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1 atmel MSL3080 8 string 60ma led drivers with integrated boost controller full datasheet features: ? drives 8 parallel 60ma led strings at up to 40v led string voltage ? integrated boost controller ? offers true 12-bit led dimming at 120hz ? string open circuit and led short circuit fault detection and automatic shut down ? 3% current accuracy and current balance ? single resistor sets current for all led strings ? external pwm dimming ? internal pwm dimming control engine ? single pwm input sets dimming duty cycle and frequency ? internal pwm dimming (use optional) ? synchronizes pwm dimming to lcd panel refresh rate ? frequency multiplier allows pwm dimming at multiples of lcd panel refresh frequency (see programming guide) ? 1mhz i2c/smbus interface; use optional ? resistor programmable led short circuit threshold ? die over-temperature cut-off protection ? -40c to +85c operating temperature range ? lead free, halogen free, rohs compliant package description: the MSL3080 8-channel led drivers with integrated boost regulator controller offers a complete solution to drive parallel led strings at up to 40v. the led current sinks control up to 60ma each for up to 19w of led power. the MSL3080 has eight current sinks. parallel connect the current sinks for increased string current. a single resistor sets led current, with string matching and accuracy within 3%. the advanced integrated pwm circuitry allows up to 4095:1 dimming, and offers simple pwm dimming control. external pwm dimming is controlled by a signal at the pwm input, which sets both the pwm duty cycle and frequency of the dimming signals. the internal pwm dimming is controlled by registers accessible through the i 2 c serial interface. the MSL3080 feature integrated fault detection circuitry that detects and acts upon string open-circuit and led short circuit faults, boost regulator over-voltage faults, and die over-temperature faults. a proprietary effciency optimizer maintains suffcient boost regulator output voltage to maintain led current regulation while minimizing power use. a 1mhz i 2 c/smbus serial interface allows optional dimming control, fault inspection and control of driver confguration; for serial interface information see the msl3040/50/60/80/86/87/88 programming guide. the MSL3080 is offered in the 24-pin vqfn lead-free, halogen-free, rohs compliant package and operate over -40c to +85c. dbie-20120814 msl3050/msl3060/MSL3080 datasheet preliminary i2c and smbus are trademarks of their respective owners. msl3050/60/80 preliminary datasheet revision 0.1 page 1 of 24 ? atmel inc., 2011. all rights reserved. 5, 6 and 8 string 60ma led drivers with integrated boost controller ______________ general description the msl3050/msl3060/MSL3080 multi-channel led drivers with integrated boost regulator controller offer a complete solution to drive parallel led strings at up to 40v. the led current sinks control up to 60ma each for up to 19w of led power. the msl3050 has five current sinks, the msl3060 has six and the MSL3080 has eight. parallel connect the current sinks for increased string curren t. a single resistor se ts led current, with string matching and accuracy within 3%. the advanced integrated pwm circuitry allows up to 4095:1 dimming, and offers simple pwm dimming control. external pwm dimming is controlled by a signal at the pwm input, which sets both the pwm duty cycle and frequency of the dimming signals. the internal pwm dimming is controlled by registers accessible through the i2c serial interface. the msl3050/60/80 feature integrated fault detection circuitry that detects and acts upon st ring open-circuit and led short circuit faults, boost regulator over-voltage faults, and die over- temperature faults. a proprietary efficiency opti mizer maintains sufficient boost regulator output voltage to maintain led current regulation while minimizing power use. a 1mhz i 2 c/smbus serial interface allows optional dimmi ng control, fault inspection and control of driver configuration; fo r serial interface information see the msl3050/60/80/50/ 60/80/86/87/88 programming guide. the msl3050/60/80 are offered in the 24-pin vqfn lead-free, halogen-free, rohs compliant package and operate over -40c to +85c. _____________________ applications long life, efficient led backlighting for: televisions and desktop monitors medical and industrial instrumentation automotive audi o-visual displays channel signs architectural lighting _____________ ordering information part description pkg msl3050 5-ch led driver with integrated boost controller and resistor based led short circuit threshold setting, with single pwm input. 24 pin 4 x 4 x 0.75mm vqfn msl3060 6-ch led driver with integrated boost controller and resistor based led short circuit threshold setting, with single pwm input. 24 pin 4 x 4 x 0.75mm vqfn MSL3080 8-ch led driver with integrated boost controller and resistor based led short circuit threshold setting, with single pwm input. 24 pin 4 x 4 x 0.75mm vqfn ____________________ key features ? drives 5/6/8 parallel 60ma le d strings at up to 40v led string voltage ? integrated boost controller ? offers true 12-bit led dimming at 200hz ? string open circuit and led short circuit fault detection and automatic shut down ? 3% current accuracy and current balance ? single resistor sets current for all led strings ? external pwm dimming ? internal pwm dimming control engine ? single pwm input sets dimming duty cycle and frequency ? internal pwm dimming (use optional) ? synchronizes pwm dimming to lcd panel refresh rate ? frequency multiplier allows pwm dimming at multiples of lcd panel refresh frequency (see programming guide) ? 1mhz i2c/smbus interface; use optional ? resistor programmable led short circuit threshold ? die over-temperature cut-off protection ? -40c to +85c operating temperature range ? lead free, halogen free, rohs compliant package _______________ application circuit enable v in = 5v en sda scl fltb pwm iled pgnd gnd ep str3 str2 str1 str0 cs gate fb vin pvin i 2 c interface fbi fault output pwm input comp MSL3080 str4 str5 str6 str7 v led v pwr = 12v 10 h 25m 2nf 22k 20 f 3.12k 47.5k 91.3k 60v 3a fdc 5612 10 f application circuit atmel MSL3080 datasheet 8 string 60ma led driver with integrated boost controller free datasheet http:///
2 table of contents 1.0 packages and pin connections ................................................................. 3 2.0 pin descriptions .......................................................................................... 4 3.0 absolute maximum ratings ....................................................................... 5 4.0 electrical characteristics ........................................................................... 6 5.0 typical operating characteristics ............................................................. 7 6.0 block diagram ............................................................................................. 9 7.0 typical application circuits ..................................................................... 10 8.0 detailed description ................................................................................. 13 8.1 led driver comparison ................................................................................................. 13 8.2 boost regulator overview ............................................................................................. 14 8.3 error amplifer ................................................................................................................ 14 8.4 gate driver .................................................................................................................... 15 8.5 soft-start ....................................................................................................................... 15 8.6 boost fault monitoring and protection .......................................................................... 15 8.7 led current regulators and pwm dimming modes .................................................... 15 8.8 effciency optimizer (eo) .............................................................................................. 15 8.9 fault monitoring and auto-handling .............................................................................. 15 8.10 internal supervisory and ldo ....................................................................................... 16 8.11 internal oscillator ........................................................................................................... 16 8.12 over temperature shutdown ......................................................................................... 16 8.13 power saving modes ..................................................................................................... 16 8.14 i 2 c serial interface and driver control ........................................................................... 16 9.0 application information ............................................................................ 17 9.1 bypassing vin and pvin ............................................................................................... 17 9.2 setting the led current ................................................................................................ 17 9.3 fault monitoring and automatic fault handling ............................................................. 17 9.4 setting the led short-circuit threshold ........................................................................ 17 9.5 boost regulator ............................................................................................................. 18 9.6 the effciency optimizer (eo) ....................................................................................... 19 9.7 setting the boost regulator output voltage .................................................................. 20 9.8 choosing the input and output capacitors .................................................................... 20 9.9 choosing the inductor ................................................................................................... 20 9.10 setting the external mosfet current limit .................................................................. 21 9.11 choosing the switching mosfet ................................................................................. 21 9.12 choosing the output rectifer ....................................................................................... 21 9.13 loop compensation ...................................................................................................... 21 10.0 led dimming control ............................................................................... 23 11.0 ordering information ................................................................................ 23 atmel MSL3080 datasheet 8 string 60ma led driver with integrated boost controller free datasheet http:///
3 1.0 packages and pin connections 1.1 24 pin 4 x 4 x 0.75mm vqfn package page 22 of 22 ? atmel inc., 2011. all rights reserved. p hase s hifted led d imming signals by default, string pwm dimming is staggered in time to r educe the transient current demand on the boost regulator. the msl3040/41 automatically determine the stagger times based on the number of enabled strings and the pwm dimming frequency. package information page 22 of 22 ? atmel inc., 2011. all rights reserved. p hase s hifted led d imming signals by default, string pwm dimming is staggered in time to r educe the transient current demand on the boost regulator. the msl3040/41 automatically determine the stagger times based on the number of enabled strings and the pwm dimming frequency. package information page 22 of 22 ? atmel inc., 2011. all rights reserved. p hase s hifted led d imming signals by default, string pwm dimming is staggered in time to r educe the transient current demand on the boost regulator. the msl3040/41 automatically determine the stagger times based on the number of enabled strings and the pwm dimming frequency. package information page 22 of 22 ? atmel inc., 2011. all rights reserved. p hase s hifted led d imming signals by default, string pwm dimming is staggered in time to r educe the transient current demand on the boost regulator. the msl3040/41 automatically determine the stagger times based on the number of enabled strings and the pwm dimming frequency. package information msl3050/msl3060/MSL3080 datasheet preliminary msl3050/60/80 preliminary datasheet revision 0.1 page 2 of 24 ? atmel inc., 2011. all rights reserved. package pin description gnd comp cs en fltb pvin 24 23 22 21 20 19 fb 1 18 gate msl3050 (top view) vin 2 17 pgnd sda 3 16 iled scl 4 15 cgnd scth 5 14 pwm str0 6 13 cgnd 7 8 9 10 11 12 str1 str2 str3 str4 cgnd cgnd gnd comp cs en fltb pvin 24 23 22 21 20 19 fb 1 18 gate msl3060 (top view) vin 2 17 pgnd sda 3 16 iled scl 4 15 cgnd scth 5 14 pwm str0 6 13 cgnd 7 8 9 10 11 12 str1 str2 str3 str4 str5 cgnd gnd comp cs en fltb pvin 24 23 22 21 20 19 fb 1 18 gate MSL3080 (top view) vin 2 17 pgnd sda 3 16 iled scl 4 15 cgnd scth 5 14 pwm str0 6 13 str7 7 8 9 10 11 12 str1 str2 str3 str4 str5 str6 atmel MSL3080 datasheet 8 string 60ma led driver with integrated boost controller free datasheet http:///
4 2.0 pin descriptions table 2.1 pin assignments name MSL3080 pin description fb 1 v led voltage regulator feedback input: connect a resistive voltage divider from the boost regulator output, v led , to fb to set the un- optimized boost regulator output voltage. the feedback regulation voltage is 2.5v. vin 2 power supply input: power supply input. apply 4.5v to 5.5v to vin. decouple vin to gnd a 1 f or greater capacitor placed close to vin. sda 3 i2c serial data i/o: sda is the i2c serial interface data input/output. connect sda to vin when unused. for interface information see the msl3040/50/60/80/86/87/88 programming guide. scl 4 i2c serial clock input: scl is the i2c serial interface clock input. connect scl to vin when unused. for interface information see the msl3040/50/60/80/86/87/88 programming guide . scth 5 string short circuit threshold level setting input: scth programs the led string short-circuit detection threshold. connect a resistor from scth to gnd to set the short-circuit threshold level to 4.9v (1k), 5.8v (27k), 6.8v (68k) or 7.6v (330k). a short circuit is detected when the str n voltage is above the threshold while strn is on. see the section setting the led short-circuit threshold on page 17 for information. str0 6 led string 0 current sink: connect the cathode end of series led string 0 to str0. if not used, connect str0 to gnd. str1 7 led string 1 current sink: connect the cathode end of series led string 1 to str1. if not used, connect str1 to gnd. str2 8 led string 2 current sink: connect the cathode end of series led string 2 to str2. if not used, connect str2 to gnd. str3 9 led string 3 current sink: connect the cathode end of series led string 3 to str3. if not used, connect str3 to gnd. str4 10 led string 4 current sink: connect the cathode end of series led string 4 to str4. if not used, connect str4 to gnd. str5 11 led string 5 current sink: connect the cathode end of series led string 5 to str5. if not used, connect str5 to gnd. str6 12 led string 6 current sink: connect the cathode end of series led string 6 to str6. if not used, connect str6 to gnd. str7 13 led string 7 current sink: connect the cathode end of series led string 7 to str7. if not used, connect str7 to gnd. cgnd 15 connect to ground: connect cgnd to gnd close to the driver. pwm 14 pwm dimming and synchronization input: drive pwm with a pulse-width modulated signal with duty cycle of 0% to 100% and frequency of 20hz to 50khz to control the duty cycle and the frequency of all led strings. for serial interface controlled pwm dimming connect pwm to gnd and refer to the register definitions section for registers 0x10 through 0x14 in the msl3040/50/60/80/86/87/88 programming guide . iled 16 maximum led current control input: connect a resistor from iled to gnd to set the full-scale led current. see the section setting the led current on page 17 for more information. pgnd 17 power ground: ground of the boost regulator gate driver. connect pgnd to gnd, ep and cgnd as close to the MSL3080 as possible. gate 18 gate drive output: connect gate to the gate of the boost regulator switching mosfet pvin 19 boost regulator power supply input: pvin is the power supply input for the external mosfet gate driver. apply 4.5v to 5.5v to pvin. decouple pvin with two 1 f capacitors placed close to pvin. fltb 20 fault output: fltb sinks current to gnd when a fault is detected. clear faults by toggling en low and then high, by cycling input power off and on, or through the i 2 c serial interface; see the msl3040/50/60/80/86/87/88 programming guide for information. en 21 enable input: drive en high to turn on the device, drive it low to turn it off. for automatic startup connect en to vin. toggle en low then high to reset fltb, or reset it through the i2c serial interface. cs 22 boost regulator current sense input: connect the current sense resistor from cs and the mosfet source to gnd to set the boost regulator current limit. the current limit threshold is 100mv. see the section setting the external mosfet current limit beginning on page 21 for more comp 23 boost regulator compensation node: connect the compensation network components from comp to fb to compensate the boost regulator control loop, as shown in the typical applications circuit on page 10. see the section loop compensation beginning on page 21 for more information. gnd 24 signal ground: connect gnd to ep, pgnd and cgnd as close to the device as possible. ep ep exposed die-attach paddle: connect ep to gnd, cgnd, pgnd and to the system ground. ep is the return path for the led current as well as the primary thermal path to remove heat generated in the MSL3080. use a large circuit board trace to connect from ep to the boost supply output capacitor ground and to the input supply ground return. connect ep to a large copper ground plane for best thermal and electrical performance. atmel MSL3080 datasheet 8 string 60ma led driver with integrated boost controller free datasheet http:///
5 3.0 absolute maximum ratings voltage (with respect to gnd) vin, pvin, en, sda, scl, pwm, fltb, scth, iled, cs, comp, fb, gate ............................................................... -0.3v to +5.5v str0 to str7 ................................................................................................................................................................... -0.3v to +40v pvin to vin ....................................................................................................................................................................................... 1v pgnd, cgnd, ep ........................................................................................................................................................... -50mv to 50mv current (into pin) vin ................................................................................................................................................................................................. 50ma gate, pvin ............................................................................................................................................................................... 1250ma str0 to str7, cgnd ..................................................................................................................................................................... 75ma ep, pgnd, gnd ......................................................................................................................................................................... -1000ma all other pins ..................................................................................................................................................................... -20ma to 20ma continuous power dissipation 24-pin 4mm x 4mm vqfn (derate 25mw/c above t a = +70c) .............................................................................................. 1850mw ambient operating temperature range t a = t min to t max .......................................................................................................... -40c to +85c junction to ambient thermal resistance ( ja ), 4-layer (note 8) ............................................................................................................ 29c/w junction to ambient thermal resistance ( ja ), 2-layer (note 8) ............................................................................................................ 38c/w junction to case thermal resistance ( jc ) ............................................................................................................................................ 8.6c/w junction temperature ............................................................................................................................................................................. +125c storage temperature range ..................................................................................................................................................... -65c to +125c lead soldering temperature, 10s ............................................................................................................................................................ +300c atmel MSL3080 datasheet 8 string 60ma led driver with integrated boost controller free datasheet http:///
6 4.0 electrical characteristics v vin = 5v, v en = 5v, default register settings of table 1, ta = -40c to 85c, unless otherwise noted. typical values are at ta = +25c parameter conditions and notes min typ max unit dc electrical characteristics vin operating supply voltage 4.5 5.5 v vin operating supply current all strn outputs 100% duty 18 ma vin shutdown supply current en = gnd 1 a sda, scl, pwm, sync input high voltage 1.82 v sda, scl, pwm, sync input low voltage 0.72 v minimum pwm on-time 400 ns pwm, sync input frequency range 20 200 50,000 hz sda, fltb output low voltage sinking 6ma 0.4 v en threshold v en rising 1.5 v iled regulation voltage minimum r iled = 60k 1.25 v str0 to str7 led regulation current r iled = 100k , ta= 25c v strn = 1v 58.2 60.0 61.8 ma str0 to str7 led current load regulation r iled = 100k v strn = 1v to 5v 0.15 %/v str0 to str7 led current matching string to average of all strings -3 3 % str0 to str7 minimum headroom v strn = 60ma 0.5 v str0 to str7 short circuit fault threshold r scth = 1.0k 3.98 4.96 v fb feedback output current fbo dac = 0xff, v fb = 0 224 350 a fb feedback output current step size 1.1 a fbi input disable threshold 50 mv thermal shutdown temperature temperature rising, 10c hysteresis 135 c boost regulator electrical characteristics switching frequency 569 665 762 khz gate voltage rise/fall time c gate = 1nf 50 ns cs current limit threshold voltage 75 111 147 mv maximum duty cycle at factory set boost frequency 90.1 % minimum on time f boost = 350khz to 1mhz (contact factory for boost frequencies different from 625khz) 241 300 ns boost regulator leading-edge blanking period 130 ns fb regulation voltage 2.4 2.5 2.6 v i2c switching characteristics scl clock frequency 1/t scl bus timeout disabled (note 1) 0 1000 khz bus timeout period t timeout ta = 25c (note 7) 29 30 ms stop to start condition bus free time t buf (note 7) 0.5 s repeated start condition hold time t hd:sta (note 7) 0.26 s repeated start condition setup time t su:sta (note 7) 0.26 s stop condition setup time t su:stop (note 7) 0.26 s sda data hold time t hd:dat (note 7) 0 ns sda data valid acknowledge time t vd:ack (note 2) (note 7) 0.05 0.55 s sda data valid time t vd:dat (note 3) (note 7) 0.05 0.55 s sda data set-up time t su:dat (note 7) 100 ns scl clock low period t low (note 7) 0.5 s scl clock high period t high (note 7) 0.26 s sda, scl fall time t f (note 4) (note 5) (note 7) 120 ns sda, scl rise time t r (note 7) 120 ns sda, scl input suppression filter period t sp (note 6) (note 7) 50 ns note 1. minimum scl clock frequency is limited by the bus timeout feature, which resets the serial bus interface if either sda or scl is held low for timeout. note 2. tvd:ack = scl low to sda (out) low acknowledge time. note 3. t vd:dat = minimum sda output data-valid time following scl low transition. note 4. a master device must internally provide an sda hold time of at least 300ns to ensure an scl low state. note 5. the maximum sda and scl rise times is 300ns. the maximum sda fall time is 250ns. this allows series protection resistors to be connected between sda and scl inputs and the sda/scl bus lines without exceeding the maximum allowable rise time. note 6. MSL3080 include input flters on sda and scl that suppress input noise less than 50ns note 7. parameter is guaranteed by design and not production tested. note 8. per jedec specifcation jesd51-5 and jesd51-12. note 9. tests performed at ta = 25c, specifcations over temperature guaranteed by design. atmel MSL3080 datasheet 8 string 60ma led driver with integrated boost controller free datasheet http:///
7 5.0 typical operating characteristics (typical operating circuit, unless otherwise stated, ta = +25c, unless otherwise noted) msl3050/msl3060/MSL3080 datasheet preliminary msl3050/60/80 preliminary datasheet revision 0.1 page 6 of 24 ? atmel inc., 2011. all rights reserved. typical operating characteristics (typical operating circuit, unless otherwise stated) boost regulator efficiency vs. output current 50 55 60 65 70 75 80 85 90 95 100 0 200 400 600 800 1,000 output current (ma) efficiency (% ) v pwr = 12v v led ? 37v f boost = 625khz str n current vs. r i set 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 10 100 1000 r iset (k ? ) str n current (m a supply current vs. supply voltage 0.01 0.1 1 10 100 1000 10000 4.5 4.6 4.7 4.8 4.9 5.0 5.1 5.2 5.3 5.4 5.5 v in (v) i in (a) en = 0 en = 1 sleep = slppwrsv = 1 en = 1 sleep = slppwrsv = 0 boost not sw itching start-up waveforms ch1 = v en , ch2 = v led , ch3 = v strx , ch4 = i pwr msl3050/msl3060/MSL3080 datasheet preliminary msl3050/60/80 preliminary datasheet revision 0.1 page 7 of 24 ? atmel inc., 2011. all rights reserved. start-up waveforms (zoom) ch1 = v en , ch2 = v led , ch3 = v strx , ch4 = i pwr auto calibration ch2 = v led , ch3 = v strx boost waveforms 10% led duty cycle ch1 = v led , ch2 = v gate , ch3 = i inductor boost waveforms 100% led duty cycle ch1 = v led , ch2 = v gate , ch3 = i inductor 0.01 0.1 1 10 100 1000 10000 100000 1000000 4.5 4.6 4.7 4.8 4.9 5.0 5.1 5.2 5.3 5.4 5.5 i in (a) v in (v) supply current vs. supply voltage en = 0 en = 1 sleep = slppwrsv = 1 en = 1 sleep = slppwrsv = 0 boost not switching atmel MSL3080 datasheet 8 string 60ma led driver with integrated boost controller free datasheet http:///
8 5.0 typical operating characteristics (continued) (typical operating circuit, unless otherwise stated, ta = +25c, unless otherwise noted) msl3050/msl3060/MSL3080 datasheet preliminary msl3050/60/80 preliminary datasheet revision 0.1 page 8 of 24 ? atmel inc., 2011. all rights reserved. boost regulator waveforms 10% to 99.5% led duty cycle ch1 = v led , ch2 = v gate , ch3 = v pwm , ch4 = i inductor automatic phase shifted pwm dimming ch1 = v str0 , ch2 = v str2 , ch3 = v str4 , ch4 = v str6 boost regulator gate drive rise/fall with 3nf capacitive load ch2 = v gate msl3050/msl3060/MSL3080 datasheet preliminary msl3050/60/80 preliminary datasheet revision 0.1 page 7 of 24 ? atmel inc., 2011. all rights reserved. start-up waveforms (zoom) ch1 = v en , ch2 = v led , ch3 = v strx , ch4 = i pwr auto calibration ch2 = v led , ch3 = v strx boost waveforms 10% led duty cycle ch1 = v led , ch2 = v gate , ch3 = i inductor boost waveforms 100% led duty cycle ch1 = v led , ch2 = v gate , ch3 = i inductor driver fall time this scope image shows the voltage (vstr0) and current (istr0) waveforms for string zero, and their turn-off fall times. also shown is the string power supply output (vled), which shows very little disturbance. for this photo string 0 is enabled with all other strings disabled, and a 220pf capacitor in series with a 11 resistor in series is placed from str0 to gnd at the device. driver rise time this scope image shows the voltage (vstr0) and current (istr0) waveforms for string zero, and their turn-on rise times and delay from pwm rising. also shown is the string power supply output (vled), which shows little disturbance. for this photo string 0 is enabled with all other strings disabled. atmel MSL3080 datasheet 8 string 60ma led driver with integrated boost controller free datasheet http:///
9 6.0 block diagram figure 6.1. block diagram msl3050/msl3060/MSL3080 datasheet preliminary msl3050/60/80 preliminary datasheet revision 0.1 page 9 of 24 ? atmel inc., 2011. all rights reserved. block diagram figure 1. msl3050/msl3060/MSL3080 block diagram MSL3080 atmel MSL3080 datasheet 8 string 60ma led driver with integrated boost controller free datasheet http:///
10 7.0 typical application circuits figure 7.1. typical operating circuit for eight 60ma strings of 10 white leds each. msl3050/msl3060/MSL3080 datasheet preliminary msl3050/60/80 preliminary datasheet revision 0.1 page 10 of 24 ? atmel inc., 2011. all rights reserved. typical application circuits enable v in = 5v en sda scl fltb pwm iled pgnd ep gnd str3 str2 str1 str0 cs gate fb vin pvin i 2 c interface cgnd fault output pwm input comp MSL3080 str4 str5 str6 str7 v led v pwr = 12v 10 h 25m 2nf 22k 2x 10 f 3.12k 47.5k 93.1k scth 82k 10 f 2x 1 f 1 f b380 fdc5612 18 22 1 23 6 7 8 9 10 11 12 13 24 17 15 16 5 20 14 4 3 21 2 19 figure 2. typical operating circuit for ei ght 60ma strings of 10 white leds each. atmel MSL3080 datasheet 8 string 60ma led driver with integrated boost controller free datasheet http:///
11 figure 7.2. typical operating circuit for four 120ma strings of 10 white leds each. msl3050/msl3060/MSL3080 datasheet preliminary msl3050/60/80 preliminary datasheet revision 0.1 page 11 of 24 ? atmel inc., 2011. all rights reserved. enable v in = 5v en sda scl fltb pwm iled pgnd ep gnd str3 str2 str1 str0 cs gate fb vin pvin i 2 c interface cgnd fault output pwm input comp MSL3080 str4 str5 str6 str7 v led v pwr = 12v 10 h 25m 2nf 22k 2x 10 f 3.12k 47.5k 93.1k scth 82k 10 f 2x 1 f 1 f b380 fdc5612 18 22 1 23 6 7 8 9 10 11 12 13 24 17 15 16 5 20 14 4 3 21 2 19 figure 3. typical operating circuit for four 120ma strings of 10 white leds each. atmel MSL3080 datasheet 8 string 60ma led driver with integrated boost controller free datasheet http:///
12 figure 7.3. typical operating circuit for one 480ma string of 10 white leds. msl3050/msl3060/MSL3080 datasheet preliminary msl3050/60/80 preliminary datasheet revision 0.1 page 12 of 24 ? atmel inc., 2011. all rights reserved. enable v in = 5v en sda scl fltb pwm iled pgnd ep gnd str3 str2 str1 str0 cs gate fb vin pvin i 2 c interface cgnd fault output pwm input comp MSL3080 str4 str5 str6 str7 v led v pwr = 12v 10 h 25m 2nf 22k 2x 10 f 3.12k 47.5k 93.1k scth 82k 10 f 2x 1 f 1 f b380 fdc5612 18 22 1 23 6 7 8 9 10 11 12 13 24 17 15 16 5 20 14 4 3 21 2 19 figure 4. typical operating circuit for one 480ma string of 10 white leds. detailed description the msl3050/msl3060/MSL3080 are led drivers with five, six and eight internal current regulators respectively, each capable of driving up to 60ma led curr ent they feature an integrated boost re gulator controller with a proprietary efficiency optimizer voltage control algorithm that lowers power use to the minimum required to assure led current regulation. the driver outputs allow parallel connection to in crease string current, at the ex pense of the number of strings, and a single resistor sets the current for all strings. the drivers support 12-bit pwm led dimming ratios. the driver synchronizes led dimming and controls duty cycle with a single external digital signal at the pwm input. the msl3050/60/80 include comprehensive fault monitoring and automatic fault handling. automatic fault handling allows the drivers to operate without any microcontroller or fpga, while optional control via i 2 c allows customized fault handling and driver control for more complex applications. all driv ers also feature optional register-set pwm dimming, fault management and other controls via the i 2 c serial interface; for interface information see the msl3050/60/80/50/60/80/86/87/88 programming guide. the small 4x4mm vqfn package allows a small overall le d driver solution, while maintaining high package power dissipation for high output power capability. atmel MSL3080 datasheet 8 string 60ma led driver with integrated boost controller free datasheet http:///
13 8.0 detailed description the MSL3080 is an led driver with eight internal current regulators, each capable of driving up to 60ma led current. they feature an integrated boost regulator controller with a proprietary effciency optimizer voltage control algorithm that lowers power use to the minimum required to assure led current regulation. the driver outputs allow parallel connection to increase string current, at the expense of the number of strings, and a single resistor sets the current for all strings. the drivers support 12-bit pwm led dimming ratios. the driver synchronizes led dimming and controls duty cycle with a single external digital signal at the pwm input. the MSL3080 includes comprehensive fault monitoring and automatic fault handling. automatic fault handling allows the drivers to operate without any microcontroller or fpga, while optional control via i 2 c allows customized fault handling and driver control for more complex applications. all drivers also feature optional register-set pwm dimming, fault management and other controls via the i 2 c serial interface; for interface information see the msl3040/50/60/80/86/87/88 programming guide. the small 4x4mm vqfn package allows a small overall led driver solution, while maintaining high package power dissipation for high output power capability 8.1 led driver comparison table 8.1. led driver comparison with similar parts part number of led strings max current per string phase shifted string drivers internal boost controller resistor set led short circuit threshold separate sync input*** best for msl3086 8 60ma yes yes yes no monitor, industrial panel msl3087* 8 60ma yes no yes no small tv msl3088 8 60ma yes yes no yes small tv MSL3080 8 60ma no yes yes no monitor, industrial panel 4** 120ma no yes yes no monitor, industrial panel 2** 240ma no yes yes no monitor, industrial panel 1** 480ma no yes yes no monitor, industrial panel msl3040* 4 120ma yes yes yes no monitor, automotive msl3041* 4 120ma yes yes yes yes monitor, automotive msl3050* 5 60ma no yes yes no industrial panel 1** 300ma no yes yes no industrial panel msl3060* 6 60ma no yes yes no monitor, industrial panel 3** 120ma no yes yes no monitor, industrial panel 2** 180ma no yes yes no monitor, industrial panel 1** 360ma no yes yes no monitor, industrial panel * future product, contact factory for information. ** drivers without phase shift allow parallel connection of string drive outputs for increased string current. *** drivers with separate sync input expect two control signals, one for dimming duty cycle and one for dimming frequency. atmel MSL3080 datasheet 8 string 60ma led driver with integrated boost controller free datasheet http:///
14 8.2 boost regulator overview the MSL3080 boost regulator boosts the input voltage up to the regulated output voltage (for design details see the section boost regulator beginning on page 17, the following text presents an overview of the boost regulator controller). the boost regulator uses an external switching mosfet, current sense resistor, inductor, rectifer, and input and output capacitors (figure 8.1). external mosfet and current sense resistor allow the boost regulator to operate over wide input and output voltage ranges, and led currents. it includes a 2.5v reference voltage, fxed slope compensation and external voltage regulator compensation to optimize the control loop for each confguration. because the boost regulator components are external it supports a number of converter topologies, such as sepic, fyback, and single-switch forward. the boost regulator includes soft-start, adjustable cycle-by-cycle current limiting, and output over- voltage fault detection. figure 8.1. power section of MSL3080 8.3 error amplifer the internal error amplifer compares the external divided output voltage at fb to the internal 2.5v reference voltage to set the regulated output voltage, v led . the error amplifer output voltage at comp is externally accessible; use it to compensate the voltage regulator. fb also drives the integrated boost over-voltage comparator that detects if the output voltage exceeds the regulation voltage, to generate a fault condition. the error amplifer internally controls the current mode pwm regulator. msl3050/msl3060/MSL3080 datasheet preliminary msl3050/60/80 preliminary datasheet revision 0.1 page 14 of 24 ? atmel inc., 2011. all rights reserved. cs gate fb comp msl3050 msl3060 MSL3080 v led v pwr l1 r cs c comp1 r comp r bottom c out c comp2 c in gnd str n led current sink efficiency optimizer soft start sense limit current gate drive + ref slope comp 0.4v r esr r top d1 q1 dropout detect compensation: c comp2 = pole c comp1 , r comp = zero a = 11 0.1 v pvin 5v 1.1v 1.5v figure 5. power section of msl3050/60/80 e rror a mplifier the internal error amplifier compares the external divided outpu t voltage at fb to the internal 2.5v reference voltage to set the regulated output voltage, v led . the error amplifier output voltage at comp is externally accessible; use it to compensate the voltage regulator. fb also drives the integrat ed boost over-voltage comparator that detects if the output voltage exceeds the regulation voltage, to generate a fault conditi on. the error amplifier internally controls the current mode pwm regulator. g ate d river the gate driver drives the gate of the ex ternal boost regulator switching mosfet. the drain of the switching mosfet in turn drives the boost inductor and rectifier to boost the i nput voltage to the regulated output voltage. the gate driver sources and sinks up to 1a allowing fast switching speed a nd allows the use of mosfets with high gate capacitance. the gate driver power is separated from the internal circuitr y power to reduce internal noise and to allow separate gate driver bypassing for optimal performance. s oft -s tart the boost regulator includes a built in soft-start to prevent excessive input current overshoot at turn-on. the soft-start ramps the output regulation voltage from 0v at turn-on to t he as-configured regulation output voltage over 1.6ms. note that the boost regulator only controls output voltages greater t han the input voltage; when the soft-start sets the regulation voltage below the input voltage, the actual output voltage remains at approximately the input voltage. MSL3080 atmel MSL3080 datasheet 8 string 60ma led driver with integrated boost controller free datasheet http:///
15 8.4 gate driver the gate driver drives the gate of the external boost regulator switching mosfet. the drain of the switching mosfet in turn drives the boost inductor and rectifer to boost the input voltage to the regulated output voltage. the gate driver sources and sinks up to 1a allowing fast switching speed and allows the use of mosfets with high gate capacitance. the gate driver power is separated from the internal circuitry power to reduce internal noise and to allow separate gate driver bypassing for optimal performance. 8.5 soft-start the boost regulator includes a built in soft-start to prevent excessive input current overshoot at turn-on. the soft-start ramps the output regulation voltage from 0v at turn-on to the as-confgured regulation output voltage over 1.6ms. note that the boost regulator only controls output voltages greater than the input voltage; when the soft-start sets the regulation voltage below the input voltage, the actual output voltage remains at approximately the input voltage. 8.6 boost fault monitoring and protection the boost regulator includes fault monitoring and protection circuits to indicate faults and prevent damage to the boost regulator or other circuitry. the boost regulator has cycle by cycle current limiting that prevents excessive current through the power mosfet. the current limit is has a fxed threshold voltage across the current sense resistor , thus set the current limit by choosing the proper value current sense resistor. the boost regulator includes an output over-voltage fault monitor that indicates a fault when the voltage at fb exceeds the 2.8v over- voltage protection (ovp) threshold. when an over-voltage fault occurs fltb sinks current to gnd to indicate that a fault has occurred. ovp fault is non-latching, the fault clears when the over-voltage condition disappears. 8.7 led current regulators and pwm dimming modes the MSL3080 includes eight open-drain led current regulators that sink led current up to 60ma per channel and sustain up to 40v, allowing them to drive up to 10 white leds each. the current regulators inform the effciency optimizers, which in turn control the boost regulator output voltage to minimize led voltage while maintaining suffcient headroom for the led current regulators. set the led regulation current using a single resistor from iled to gnd. led dimming is by pwm, and is by default controlled through an external signal, or optionally by internal registers accessed through the i2c compatible serial interface (for interface information see the msl3040/50/60/80/86/87/88 programming guide ). the drivers feature synchronized dimming, where all pwm dimming outputs sink current in unison. 8.8 effciency optimizer (eo) the effciency optimizer monitors the led string drivers and controls the boost regulator output voltage to minimize led current regulator overhead voltage while maintaining suffcient voltage for accurate current regulation. the effciency optimizer injects a current into the boost regulator fb input node to reduce the boost regulator output voltage. the effciency optimizer has two modes of operation, initial calibration and auto calibration. initial calibration happens at turn-on and optimizes boost regulator output voltage. auto calibration happens once per second to re-optimize the boost output voltage in response to changing led forward voltage due to aging or temperature effects. 8.9 fault monitoring and auto-handling the MSL3080 includes comprehensive fault monitoring and corrective action. the led current regulators are monitored for led string open circuit and led short circuit faults. it also monitors the boost regulator for output over-voltage. strings with led short circuit or open circuit faults are turned off and ignored by the effciency optimizer. fltb sinks current to gnd when a fault is detected. the boost over-voltage fault does not latch, the fault goes away when the fault condition no longer exists and fltb is released; all other faults latch. clear faults by toggling en low and then high, or by cycling input power off and on. additionally, fault control is available through the i 2 c compatible serial interface; see the msl3040/50/60/80/86/87/88 programming guide for information. atmel MSL3080 datasheet 8 string 60ma led driver with integrated boost controller free datasheet http:///
16 8.10 internal supervisory and ldo the MSL3080 has a power-on-reset circuit that monitors vin and allows operation when vin exceeds 4.25v. the MSL3080 has built-in ldos that generate 2.5v to power the logic and oscillator sections. an integrated supervisor ensures that the ldo and internal oscillator are stable before enabling the boost controller. the boost controller goes through a soft-start before the led drivers are enabled. 8.11 internal oscillator the MSL3080 includes a 20mhz internal oscillator that is divided down to drive the boost controller, and the led pwm engine. the oscillator is factory trimmed. contact the factory if required to change the 20mhz default oscillator frequency; available frequencies fall between 16mhz and 24mhz. 8.12 over temperature shutdown the MSL3080 includes automatic over-temperature shutdown. when the die temperature exceeds 135c, the driver turns off, as if en is pulled low, and is held off until the die temperature drops below 120c, at which time it turns back on. while MSL3080 is in over- temperature shutdown the onboard regulators are off, register values reset to their power-on default values, and the serial interface is disabled. 8.13 power saving modes the MSL3080 has 3 primary power save modes available through the i 2 c compatible serial interface. see the msl3040/50/60/80/86/87/88 programming guide for information. 8.14 i 2 c serial interface and driver control the i 2 c serial interface, whose use is optional, allows control of pwm dimming, fault monitoring, and various other control functions. for a detailed explanation of interface operation see the msl3040/50/60/80/86/87/88 programming guide. atmel MSL3080 datasheet 8 string 60ma led driver with integrated boost controller free datasheet http:///
17 9.0 application information 9.1 bypassing vin and pvin bypass vin with a capacitor of at least 1f. bypass pvin to pgnd with at least 2f. place all bypass capacitors close to the MSL3080. 9.2 setting the led current set the on-current for all led strings with a resistor from iled to gnd. choose the resistor using: where i led is the led full-scale current in amps. the maximum led current per-string is 60ma. driving all eight strings with 60ma at high duty cycles and elevated ambient temperatures requires proper thermal management to avoid over-temperature shutdown. connect the exposed pad (ep) to a large copper ground plane for best thermal and electrical performance. 9.3 fault monitoring and automatic fault handling the MSL3080 monitors the led strings and boost regulator output voltage to detect led short-circuit, led string open-circuit and boost over-voltage faults. string faults latch the open drain fault output fltb low. a boost over-voltage fault pulls fltb low but does not latch. when shorted leds are detected in a string, the driver disables and the effciency optimizer stops monitoring it. the MSL3080 fags these strings as faults in registers 0x05 through 0x08, pulls fltb low and recalibrates the led power supply voltage. set the short circuit voltage threshold with a resistor between scth and gnd, as explained in the section setting the led short-circuit threshold beginning on page 17. for information about the fault registers and the i 2 c compatible serial interface see the msl3040/50/60/80/86/87/88 programming guide. when an open circuit occurs, the effciency optimizer detects a loss of current regulation which must persist for greater than 2 s to be detected. the minimum on-time for the strings is 2 s. in this case the effciency optimizer increases the led voltage (boost regulator output voltage), in an attempt to bring the led current back in to regulation. this continues until the voltage is at the maximum level. the MSL3080 then determines that any led strings that are not regulating current are open circuit. it disables those strings, fags them as faults in registers 0x05 through 0x08, pulls fltb low and recalibrates the led power supply voltage. when the boost regulator is at its maximum value fctitious led short circuit faults can occur. toggle en low and then high to clear all faults and return the MSL3080 to controlling and monitoring all led strings. fault conditions that persist re-establish fault responses. for information about the fault registers and the i 2 c compatible serial interface see the msl3040/50/60/80/86/87/88 programming guide . 9.4 setting the led short-circuit threshold when a given string, strn, is sinking led string current, the fault detection circuit monitors the str n voltage. typical optimized str n on-voltage is 0.5v. when one or more leds of a string are shorted, the str n voltage increases above the nominal. when the voltage is above the short-circuit threshold the fault circuit generates an led short circuit fault. in most cases, two leds in a string must be shorted to cause a short circuit fault, but because led v f differs for different leds, the number of shorted leds required to generate a fault varies.set the led short-circuit threshold with a resistor from scth to gnd using: table 9.1 short circuit threshold resistor r scth threshold voltage 1.0k (or gnd) 4.9v 27k 5.8v 68k 6.8v 330k (or open) 7.6v r scth is measured only at power up, and when en is taken high, to set the threshold level. additionally, register 0x04 holds the short circuit threshold level, changeable through the i 2 c compatible serial interface. for information about the short circuit threshold register and the serial interface see the msl3040/50/60/80/86/87/88 programming guide. atmel MSL3080 datasheet 8 string 60ma led driver with integrated boost controller free datasheet http:///
18 figure 9.1 open-circuit and short-circuit detection block diagram 9.5 boost regulator the boost regulator boosts the input voltage to the regulated output voltage that drives the led anodes. the MSL3080 boost regulator uses an external mosfet switch and current sense resistor, allowing a wide variety of input/output voltage combinations and load currents. the boost regulator switching frequency is 625khz. switching frequencies of 350khz, 500khz, 750khz, 875khz and 1mhz are also available; contact the factory for information. atmel MSL3080 datasheet 8 string 60ma led driver with integrated boost controller free datasheet http:///
19 9.6 the effciency optimizer (eo) a voltage divider from the boost regulator output voltage to fb sets the regulation voltage (r top and r bottom in figure 8.1 on page 14). the eo improves power effciency by dynamically adjusting the power supply output voltage to the minimum required to power the leds. this ensures that there is suffcient voltage available for led current regulation, and good power supply noise rejection, while minimizing power dissipation. it does this by injecting a current into the fb input over 256 steps (8-bit resolution). when turned on, either by applying input voltage to vin while en is high, or by driving en high with voltage applied to vin, the eo begins an initial calibration cycle by monitoring the led current regulators. if all the current regulators maintain led current regulation the eo output current is increased to reduce the boost output voltage. after the 4ms power supply settling time, it rechecks the regulators, and if they continue to maintain regulation the process repeats until one or more current regulator loses regulation. this step requires that the strings are turned on for a minimum of 2 s to detect current regulation. the eo then decreases the output current to increase boost output voltage, giving the regulator enough headroom to maintain regulation with minimal power dissipation. the oscilloscope picture figure 9.2 shows this procedure. the eo automatically re-calibrates v out every 1 second, and at any time increases the boost voltage when detects an led string with insuffcient current. figure 9.2 effciency optimizer (eo) msl3050/msl3060/MSL3080 datasheet preliminary msl3050/60/80 preliminary datasheet revision 0.1 page 19 of 24 ? atmel inc., 2011. all rights reserved. power supply noise rejection, while minimizing power dissipation. it does this by injecting a current into the fb input over 256 steps (8-bit resolution). when turned on, either by applying input voltage to vin while en is high, or by driving en high with voltage applied to vin, the eo begins an initial calibration cycle by monitori ng the led current regulators. if all the current regulators maintain led current regulation the eo output current is increased to reduce the boost output voltage. after the 4ms power supply settling time, it rechecks the regulators, and if t hey continue to maintain regulation the process repeats until one or more current regulator looses regulation. this step requi res that the strings are turned on for a minimum of 3 s to detect current regulation. the eo then de creases the output current to increase boost output voltage, giving the regulator enough headroom to maintain regulation with minimal power dissipation. the oscilloscope picture figure 7 shows this procedure. the eo automatically re-calibrates v out every 1 second, and at any time increases the boost voltage when detects an led string with insufficient current. figure 7. efficiency optimizer (eo) s etting the b oost r egulator o utput v oltage select the voltage divider resistors (r top and r bottom in figure 5 on page 14) to set the boost regulator output voltage by first determining v out(min) and v out(max) , the required minimum and maximum led string anode power supply (boost regulator) voltage, using: atmel MSL3080 datasheet 8 string 60ma led driver with integrated boost controller free datasheet http:///
20 9.7 setting the boost regulator output voltage select the voltage divider resistors (r top and r bottom in figure 8.1 on page 14) to set the boost regulator output voltage by frst determining v out(min) and v out(max) , the required minimum and maximum led string anode power supply (boost regulator) voltage, using: and where v f(min) and v f(max) are the leds minimum and maximum forward voltage drops at the full-scale current set by r iled (page 17). for example, if the led minimum forward voltage is v f(min) = 3.5v and maximum is v f(max) = 3.8v, using 10 leds in a string, the total minimum and maximum voltage drop across a string is 35v and 38v. adding allowance of 0.5v for the current regulator headroom brings v out(min) to 35.5v and v out(max) to 38.5. next determine r top using: where 350 x 10 -6 is the maximum eo output current. then determine r bottom using: where 2.5v is the internal reference voltage. 9.8 choosing the input and output capacitors the input and output capacitors carry the high frequency current due to the boost regulator switching. the input capacitor prevents this high frequency current from travelling back to the input voltage source, reducing conducted and radiated noise. the output capacitor prevents high frequency current to the load, in this case the leds, and also prevents conducted and radiated noise. the output capacitors also have a large effect on the boost regulator loop stability and transient response, and so are critical to optimal boost regulator operation. use ceramic input and output capacitors that keep their rated capacitance values at the expected operating voltages. the typical application circuit on page 10 shows recommended values for and 10 leds and 60ma per string. use a bulk electrolytic capacitor where power enters the circuit board. 9.9 choosing the inductor the boost regulator inductor takes the current from the input source and directs that current to the load. using the proper inductor is critical to proper boost regulator operation. choose an inductor with suffcient inductance to keep the inductor ripple current within limits, and with suffcient current handling capability for steady-state and transient conditions. the boost regulator switching causes ripple current through the inductor. the current rises during the on-time and falls during the off time. the slope of the inductor current is a function of the voltage across the inductor, and so the total change in current, i l , is the current slope multiplied by the time in that phase (on time, t on , or off time, t off ). in steady-state, where the load current, input voltage, and output voltage are all constant, the inductor current does not change over one cycle, and so the amount the current rises during the on time is the same as the amount the current drops during the off time. calculate the duty cycle (equal to the on-time divided by the switching period) using: where v out is the output voltage and v in is the input voltage. calculate the on-time in seconds using: where f sw is the boost regulator switching frequency. calculate the inductor ripple current using: where l is the inductance value in henrys. choose a value for l that produces a ripple current in the range of 25% to 50% of the steady state dc inductor current. the steady state dc inductor current is equal to the input current. estimate the steady-state dc input current using: where i load is the sum of all strings steady-state led currents with all leds on simultaneously, v out is the maximum (un-optimized) boost regulator output voltage, and v in is the minimum boost regulator input voltage. msl3050/msl3060/MSL3080 datasheet preliminary msl3050/60/80 preliminary datasheet revision 0.1 page 20 of 24 ? atmel inc., 2011. all rights reserved. ?? ? ? 5 . 0 # ) ( ) ( ? ? ? ofleds v v min f min out , and ?? ? ? 5 . 0 # ) ( ) ( ? ? ? ofleds v v max f max out , where v f(min) and v f(max) are the led?s minimum and maximum forward vo ltage drops at the full-scale current set by r iled (page 16). for example, if the led minimum forward voltage is v f(min) = 3.5v and maximum is v f(max) = 3.8v, using 10 leds in a string, the total minimum and maximum voltage drop across a string is 35v and 38v. adding allowance of 0.5v for the current regulator headroom brings v out(min) to 35.5v and v out(max) to 38.5. next determine r top using: ? ? ? ? ? 6 ) ( ) ( 10 365 min out max out top v v r , where 3.65x10 -6 is the maximum eo output current. then determine r bottom using: ? ? ? ? 5 . 2 5 . 2 ) ( max out top bottom v r r , where 2.5v is the internal reference voltage. other boost regulator components use the component values shown in the typical applicatio ns circuits beginning on page 10. when custom boost regulator design is required use the guidelines presented in the following sections. c hoosing the i nput and o utput c apacitors the input and output capacitors carry the high frequency current due to the boost regulator switching. the input capacitor prevents this high frequency current from travelling back to the input voltage source, reducing conducted and radiated noise. the output capacitor prevents high frequency current to the load, in this case the leds, and also prevents conducted and radiated noise. the output capacitors also have a large effect on the boost regulator loop stability and transient response, and so are critical to optimal boost regulator operation. c hoosing the i nput and o utput c apacitors use ceramic input and output capacitors that keep their rat ed capacitance values at the expected operating voltages. the typical application circuit on page 10 shows recommended values for and 10 leds and 60ma per string. use a bulk electrolytic capacitor where power enters the circuit board. c hoosing the i nductor the boost regulator inductor takes the curr ent from the input source and directs that current to the load. using the proper inductor is critical to proper boost regulator operation. choo se an inductor with sufficient inductance to keep the inductor ripple current within limits, and with sufficient current handl ing capability for steady-state and transient conditions. the boost regulator switching causes ripple current through the inductor. the current rises during the on-time and falls during the off time. the slope of the inductor current is a function of the voltage across the inductor, and so the total change in current, ? i l , is the current slope multiplied by the time in that phase (on time, t on , or off time, t off ). in steady- state, where the load current, input voltage, and output voltage ar e all constant, the inductor current does not change over one cycle, and so the amount the current ri ses during the on time is the same as the amount the current drops during the off time. calculate the duty cycle (equal to the on-time divided by the switching period) using: ?? ? ? 5.0 # ) () ( ? ?? ofleds v v maxf maxout , where v f(min) and v f(max) are the led?s minimum and maximum forward vo ltage drops at the full-scale current set by r iled (page 14 ). for example, if the led minimum forward voltage is v f(min) = 3.5v and maximum is v f(max) = 3.8v, using 10 leds in a string, the total minimum and maximum voltage drop across a string is 35v and 38v. adding allowance of 0.5v for the current regulator headroom brings v out(min) to 35.5v and v out(max) to 38.5. next determine r top using: ? ? ? ? ? 6 )( )( 10365 minout maxout top v v r . then determine r bottom using: ? ? ?? 5.2 5.2 )( maxout top bottom v rr . c hoosing the i nput and o utput c apacitors the input and output capacitors carry the high frequency current due to the boost regulator switching. the input capacitor prevents this high frequency current from travelling back to the input voltage source, reducing conducted and radiated noise. the output capacitor prevents high frequency current to the load, in this case the leds, and also prevents conducted and radiated noise. the output capacitors also have a large effect on the boost regulator loop stability and transient response, and so are critical to optimal boost regulator operation. c hoosing the i nput and o utput c apacitors use ceramic input and output capacitors that keep their rated capacitance values at the expected operating voltages. the typical application circuit on page 10 shows recommended values for and 10 leds and 120ma per string. use a bulk electrolytic ca pacitor where pow er enters the circuit board. c hoosing the i nductor the boost regulator inductor takes the curr ent from the input source and directs that current to the load. using the proper inductor is critical to proper boost regulator operation. choo se an inductor with sufficient inductance to keep the inductor ripple current within limits, and with sufficient current handling capability for steady-state and transient conditions. the boost regulator switching causes ripple current through the inductor. the current rises during the on-time and falls during the off time. the slope of the inductor current is a function of the voltage across the inductor, and so the total change in current, ? i l , is the current slope multiplied by the time in that phase (on time, t on , or off time, t off ). in steady- state, where the load current, input voltage, and output voltage ar e all constant, the inductor current does not change over one cycle, and so the amount the current ri ses during the on time is the same as the amount the current drops during the off time. calculate the duty cycle (equal to the on-time divided by the switching period) using: in in out v vv d ? ? , where v out is the output voltage and v in is the input voltage. calculate the on-time in seconds using: sw in in out sw on fv vv f d t ? ? ?? , page 18 of 22 ? atmel inc., 2011. all rights reserved. ?? ? ? 5.0 # ) () ( ? ?? ofleds v v maxf maxout , where v f(min) and v f(max) are the led?s minimum and maximum forward vo ltage drops at the full-scale current set by r iled (page 14 ). for example, if the led minimum forward voltage is v f(min) = 3.5v and maximum is v f(max) = 3.8v, using 10 leds in a string, the total minimum and maximum voltage drop across a string is 35v and 38v. adding allowance of 0.5v for the current regulator headroom brings v out(min) to 35.5v and v out(max) to 38.5. next determine r top using: ? ? ? ? ? 6 )( )( 10365 minout maxout top v v r . then determine r bottom using: ? ? ?? 5.2 5.2 )( maxout top bottom v rr . c hoosing the i nput and o utput c apacitors the input and output capacitors carry the high frequency current due to the boost regulator switching. the input capacitor prevents this high frequency current from travelling back to the input voltage source, reducing conducted and radiated noise. the output capacitor prevents high frequency current to the load, in this case the leds, and also prevents conducted and radiated noise. the output capacitors also have a large effect on the boost regulator loop stability and transient response, and so are critical to optimal boost regulator operation. c hoosing the i nput and o utput c apacitors use ceramic input and output capacitors that keep their rated capacitance values at the expected operating voltages. the typical application circuit on page 10 shows recommended values for and 10 leds and 120ma per string. use a bulk electrolytic ca pacitor where pow er enters the circuit board. c hoosing the i nductor the boost regulator inductor takes the curr ent from the input source and directs that current to the load. using the proper inductor is critical to proper boost regulator operation. choo se an inductor with sufficient inductance to keep the inductor ripple current within limits, and with sufficient current handling capability for steady-state and transient conditions. the boost regulator switching causes ripple current through the inductor. the current rises during the on-time and falls during the off time. the slope of the inductor current is a function of the voltage across the inductor, and so the total change in current, ? i l , is the current slope multiplied by the time in that phase (on time, t on , or off time, t off ). in steady- state, where the load current, input voltage, and output voltage ar e all constant, the inductor current does not change over one cycle, and so the amount the current ri ses during the on time is the same as the amount the current drops during the off time. calculate the duty cycle (equal to the on-time divided by the switching period) using: in in out v vv d ? ? , where v out is the output voltage and v in is the input voltage. calculate the on-time in seconds using: sw in in out sw on fv vv f d t ? ? ?? , page 18 of 22 ? atmel inc., 2011. all rights reserved. ?? ? ? 5.0 # ) () ( ? ?? ofleds v v maxf maxout , where v f(min) and v f(max) are the led?s minimum and maximum forward vo ltage drops at the full-scale current set by r iled (page 14 ). for example, if the led minimum forward voltage is v f(min) = 3.5v and maximum is v f(max) = 3.8v, using 10 leds in a string, the total minimum and maximum voltage drop across a string is 35v and 38v. adding allowance of 0.5v for the current regulator headroom brings v out(min) to 35.5v and v out(max) to 38.5. next determine r top using: ? ? ? ? ? 6 )( )( 10365 minout maxout top v v r . then determine r bottom using: ? ? ?? 5.2 5.2 )( maxout top bottom v rr . c hoosing the i nput and o utput c apacitors the input and output capacitors carry the high frequency current due to the boost regulator switching. the input capacitor prevents this high frequency current from travelling back to the input voltage source, reducing conducted and radiated noise. the output capacitor prevents high frequency current to the load, in this case the leds, and also prevents conducted and radiated noise. the output capacitors also have a large effect on the boost regulator loop stability and transient response, and so are critical to optimal boost regulator operation. c hoosing the i nput and o utput c apacitors use ceramic input and output capacitors that keep their rated capacitance values at the expected operating voltages. the typical application circuit on page 10 shows recommended values for and 10 leds and 120ma per string. use a bulk electrolytic ca pacitor where pow er enters the circuit board. c hoosing the i nductor the boost regulator inductor takes the curr ent from the input source and directs that current to the load. using the proper inductor is critical to proper boost regulator operation. choo se an inductor with sufficient inductance to keep the inductor ripple current within limits, and with sufficient current handling capability for steady-state and transient conditions. the boost regulator switching causes ripple current through the inductor. the current rises during the on-time and falls during the off time. the slope of the inductor current is a function of the voltage across the inductor, and so the total change in current, ? i l , is the current slope multiplied by the time in that phase (on time, t on , or off time, t off ). in steady- state, where the load current, input voltage, and output voltage ar e all constant, the inductor current does not change over one cycle, and so the amount the current ri ses during the on time is the same as the amount the current drops during the off time. calculate the duty cycle (equal to the on-time divided by the switching period) using: in in out v vv d ? ? , where v out is the output voltage and v in is the input voltage. calculate the on-time in seconds using: sw in in out sw on fv vv f d t ? ? ?? , page 18 of 22 ? atmel inc., 2011. all rights reserved. msl3050/msl3060/MSL3080 datasheet preliminary msl3050/60/80 preliminary datasheet revision 0.1 page 21 of 24 ? atmel inc., 2011. all rights reserved. in in out v v v d ? ? , where v out is the output voltage and v in is the input voltage. calculate the on-time in seconds using: sw in in out sw on f v v v f d t ? ? ? ? , where f sw is the boost regulator switching frequency. calculate the inductor ripple current using: ?? l f v v v v l t v i sw in in out in on in l ? ? ? ? ? ? ? , where l is the inductance value in henrys. choose a value fo r l that produces a ripple current in the range of 25% to 50% of the steady state dc inductor current. the steady state dc inductor current is equal to the input current. estimate the steady-state dc input current using: in out load in v v i i , where i load is the sum of all strings steady-state led currents with all leds on simultaneously, v out is the maximum (un- optimized) boost regulator output voltage, v in is the minimum boost regulator input voltage, and n is the boost regulator efficiency. inductors have two types of maximum current ratings, rm s current and saturation current. make sure that the peak inductor current is less than the satura tion current rating. note that during load current transients, which occur whenever the leds are turned on or off (due to pwm dimming), the i nductor current may overshoot its steady state value. how much it overshoots depends on the boost regulator loop dynamics. if unsure of t he loop dynamics, a typical value to use for the overshoot is 50% of t he steady-state current. add half of the inductor ripple current to this value to determine the peak inductor current. with inductor ripple current in the 25% to 50% range, estimate the inductor rms current as 115% of the dc steady state inductor current. s etting the e xternal mosfet c urrent l imit the current sense resistor, connected from the switching mosf et source to gnd, sets the boost regulator current limit. the cycle-by-cycle current limit turns-off the boost regula tor switching mosfet when the current sense input detects instantaneous current above the current limit threshold. this causes the current to drop until the end of the switching cycle. the current limit threshold is 100mv typical, and tbd mv minimum. choose the current sense resistor value to set the current limit using: ? ? ) ( max l cs i tbd r , (tbd = the minimum cs current limit threshold vo ltage from the electrical characteristics table) where i l(max) is the maximum inductor current. when r cs is not equal to a standard 1% resistor value use the next lower value. where f sw is the boost regulator switching frequency. calculate the inductor ripple current using: l fv vv v l tv i sw out in outin onin l , where l is the inductance value in henrys. choose a value for l that produces a ripple current in the range of 25% to 50% of the steady state dc inductor current. the steady state dc inductor current is equal to the input current. estimate the steady-state dc input current using: ? ? ? ? ? ? ?? in out load in v v ii , where i load is the sum of all strings steady-state led currents with all leds on simultaneously, v out is the maximum (un- optimized) boost regulator output voltage, and v in is the minimum boost regulator input voltage. inductors have two types of maximum current ratings, rm s current and saturation current. make sure that the peak inductor current is less than the satura tion current rating. note that during load current transients, which occur whenever the leds are turned on or off (due to pwm dimming), the i nductor current may overshoot its steady state value. how much it overshoots depends on the boost regulator loop dynamics. if unsure of t he loop dynamics, a typical value to use for the overshoot is 50% of t he steady-state current. add half of the inductor ripple current to this value to determine the peak inductor current. with inductor ripple current in the 25% to 50% range, estimate the inductor rms current as 115% of the dc steady state inductor current. s etting the e xternal mosfet c urrent l imit the current sense resistor, connected from the switching mosf et source to gnd, sets the boost regulator current limit. the cycle-by-cycle current limit turns-off the boost regula tor switching mosfet when the current sense input detects instantaneous current above the current limit threshold. this causes the current to drop until the end of the switching cycle. the current limit threshold is 100mv typical, and tbd mv minimum. choose the current sense resistor value to set the current limit using: ?? )( 1.0 maxl cs i r , where i l(max) is the maximum inductor current. c hoosing the s witching mosfet the msl3040/41 use an external logic level mosfet to implement the boost converter. choose a mosfet designed to pass twice at least the peak inductor cu rrent, and that has the lowest possible r dson while maintaining minimal gate charge for fast switching speed. make sure that the mo sfet drain-source voltage rating is above the maximum un- optimized boost output voltage, with some extra margin for vo ltage overshoot due to excess ci rcuit board stray inductance and output rectifier recovery artefacts. make sure that the mosfet package can withstand the worst-case power dissipation while maintaining die temperature within the mosfet ratings. c hoosing the o utput r ectifier the output rectifier passes the inductor current to the output capacitor and load during the switching off-time. due to the high boost regulator switching frequency use a schottky rectifie r. use a schottky diode that has a current rating at least as high as that of the external mosfet, and a voltage rati ng higher than the maximum boost regulator output voltage. schottky rectifiers have very low on voltage and fast switching speed, however at high voltage and temperatures schottky leakage current can be significant. make sure that the rectifie r power dissipation is within the rectifier specifications. page 19 of 22 ? atmel inc., 2011. all rights reserved. msl3050/msl3060/MSL3080 datasheet preliminary msl3050/60/80 preliminary datasheet revision 0.1 page 20 of 24 ? atmel inc., 2011. all rights reserved. ?? ? ? 5 . 0 # ) ( ) ( ? ? ? ofleds v v min f min out , and ?? ? ? 5 . 0 # ) ( ) ( ? ? ? ofleds v v max f max out , where v f(min) and v f(max) are the led?s minimum and maximum forward vo ltage drops at the full-scale current set by r iled (page 16). for example, if the led minimum forward voltage is v f(min) = 3.5v and maximum is v f(max) = 3.8v, using 10 leds in a string, the total minimum and maximum voltage drop across a string is 35v and 38v. adding allowance of 0.5v for the current regulator headroom brings v out(min) to 35.5v and v out(max) to 38.5. next determine r top using: ? ? ? ? ? 6 ) ( ) ( 10 365 min out max out top v v r , where 3.65x10 -6 is the maximum eo output current. then determine r bottom using: ? ? ? ? 5 . 2 5 . 2 ) ( max out top bottom v r r , where 2.5v is the internal reference voltage. other boost regulator components use the component values shown in the typical applicatio ns circuits beginning on page 10. when custom boost regulator design is required use the guidelines presented in the following sections. c hoosing the i nput and o utput c apacitors the input and output capacitors carry the high frequency current due to the boost regulator switching. the input capacitor prevents this high frequency current from travelling back to the input voltage source, reducing conducted and radiated noise. the output capacitor prevents high frequency current to the load, in this case the leds, and also prevents conducted and radiated noise. the output capacitors also have a large effect on the boost regulator loop stability and transient response, and so are critical to optimal boost regulator operation. c hoosing the i nput and o utput c apacitors use ceramic input and output capacitors that keep their rat ed capacitance values at the expected operating voltages. the typical application circuit on page 10 shows recommended values for and 10 leds and 60ma per string. use a bulk electrolytic capacitor where power enters the circuit board. c hoosing the i nductor the boost regulator inductor takes the curr ent from the input source and directs that current to the load. using the proper inductor is critical to proper boost regulator operation. choo se an inductor with sufficient inductance to keep the inductor ripple current within limits, and with sufficient current handl ing capability for steady-state and transient conditions. the boost regulator switching causes ripple current through the inductor. the current rises during the on-time and falls during the off time. the slope of the inductor current is a function of the voltage across the inductor, and so the total change in current, ? i l , is the current slope multiplied by the time in that phase (on time, t on , or off time, t off ). in steady- state, where the load current, input voltage, and output voltage ar e all constant, the inductor current does not change over one cycle, and so the amount the current ri ses during the on time is the same as the amount the current drops during the off time. calculate the duty cycle (equal to the on-time divided by the switching period) using: atmel MSL3080 datasheet 8 string 60ma led driver with integrated boost controller free datasheet http:///
21 inductors have two types of maximum current ratings, rms current and saturation current. make sure that the peak inductor current is less than the saturation current rating. note that during load current transients, which occur whenever the leds are turned on or of f (due to pwm dimming), the inductor current may overshoot its steady state value. how much it overshoots depends on the boost regulator loop dynamics. if unsure of the loop dynamics, a typical value to use for the overshoot is 50% of the steady-state current. add half of the inductor ripple current to this value to determine the peak inductor current. with inductor ripple current in the 25% to 50% range, estimate the inductor rms current as 115% of the dc steady state inductor current. 9.10 setting the external mosfet current limit the current sense resistor, connected from the switching mosfet source to gnd, sets the boost regulator current limit. the cycle-by- cycle current limit turns-off the boost regulator switching mosfet when the current sense input detects instantaneous current above the current limit threshold. this causes the current to drop until the end of the switching cycle. the current limit threshold is 100mv typical, and 75mv minimum. choose the current sense resistor value to set the current limit using: where i l(max) is the maximum inductor current. when r cs is not equal to a standard 1% resistor value use the next lower value. 9.11 choosing the switching mosfet the MSL3080 uses an external logic level mosfet to drive the boost converter. choose a mosfet that can pass at least twice the peak inductor current, and that minimizes simultaneously both the mosfet on-resistance, r dson , and gate charge for fast switching speed. make sure that the mosfet drain-source voltage rating is above the maximum un-optimized boost output voltage, with some extra margin for voltage overshoot due to excess circuit board stray inductance and output rectifer recovery artefacts. assure that the mosfet is heat sunk to withstand the worst-case power dissipation while maintaining die temperature within the mosfet ratings. 9.12 choosing the output rectifer the output rectifer passes the inductor current to the output capacitor and load during the switching of f-time. due to the high boost regulator switching frequency use a schottky rectifer. use a schottky diode that has a current rating suffcient to supply the load current, and a voltage rating higher than the maximum boost regulator output voltage. schottky rectifers have very low on voltage and fast switching speed, however at high voltage and temperatures schottky leakage current can be signifcant. make sure that the rectifer power dissipation is within the rectifer specifcations. place the mosfet and rectifer close together and as close to the output capacitor(s) as possible to reduce circuit board radiated emissions. 9.13 loop compensation use a series rc network from comp to fb to compensate the MSL3080 regulation loop (figure 8.1 on page 14). the regulation loop dynamics are sensitive to output capacitor and inductor values. to begin, determine the right-half-plane zero frequency: where r load is the minimum equivalent load resistor, or the output capacitance and type of capacitor affect the regulation loop and method of compensation. in the case of ceramic capacitors the zero caused by the equivalent series resistance (esr) is at such a high frequency that it is not of consequence. in the case of electrolytic or tantalum capacitors the esr is signifcant, so must be considered when compensating the regulation loop. determine the esr zero frequency by the equation: where c out is the value of the output capacitor, and esr is the equivalent series resistance of the output capacitor. assure that the loop crossover frequency is at least 1/5th of the esr zero frequency. place the mosfet and rectifier close together and as close to the output capacitor(s) as possible to reduce circuit board radiated emissions. l oop c ompensation use a series rc network from comp to fb to compensate the msl3040/41 regulation loop ( figure 3 on page 12). the regul ation loop dynamics are sensitive to output capacitor and inductor values. to begin, determine the right-half-plane zero frequency: l r v v f load out in rhpz ? 2 2 , where r load is the minimum equivalent load resistor, or )( maxout out load i v r ? . the output capacitance and type of capacitor affect the re gulation loop and method of compensation. in the case of ceramic capacitors the zero caused by the equivalent series re sistance (esr) is at such a high frequency that it is not of consequence. in the case of electrolytic or tantalum capa citors the esr is significant, so must be considered when compensating the regulation loop. determine the esr zero frequency by the equation: out esrz cesr f ?? ? ? 2 1 where c out is the value of the output capacitor, and esr is the equivalent series resistance of the output capacitor. assure that the loop crossover frequency is at least 1/5 th of the esr zero frequency. next determine the desired crossover frequency as 1/5 th of the lower of the esr zero f esrz , the right-half-plane zero f rhpz or the switching frequency f sw . the crossover frequency equation is: ? ? ? ? ? ? ?? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? out load cs load top comp c cr r r r r f ? 2 1 11 , where f c is the crossover frequency, r top is the top side voltage divider resistor (from the output voltage to fb), r comp is the resistor of the series rc compensation network. rearrangi ng the factors of this equation yields the solution for r comp as: out c cs top comp c f rr r ? ? ? ? ?? ? 21 1 . these equations are accurate if the compensati on zero (formed by the compensation resistor r comp and the compensation capacitor c comp ) happens at a lower frequency than crossover. therefore the next step is to choose the compensation capacitor such that the compensation zero is 1/5 th of the crossover frequency, or: comp comp c compz cr f f ? 2 1 5 . solving for c comp : c comp comp fr c ? 2 5 . page 20 of 22 ? atmel inc., 2011. all rights reserved. place the mosfet and rectifier close together and as close to the output capacitor(s) as possible to reduce circuit board radiated emissions. l oop c ompensation use a series rc network from comp to fb to compensate the msl3040/41 regulation loop ( figure 3 on page 12). the regul ation loop dynamics are sensitive to output capacitor and inductor values. to begin, determine the right-half-plane zero frequency: l r v v f load out in rhpz ? 2 2 , where r load is the minimum equivalent load resistor, or )( maxout out load i v r ? . the output capacitance and type of capacitor affect the re gulation loop and method of compensation. in the case of ceramic capacitors the zero caused by the equivalent series re sistance (esr) is at such a high frequency that it is not of consequence. in the case of electrolytic or tantalum capa citors the esr is significant, so must be considered when compensating the regulation loop. determine the esr zero frequency by the equation: out esrz cesr f ?? ? ? 2 1 where c out is the value of the output capacitor, and esr is the equivalent series resistance of the output capacitor. assure that the loop crossover frequency is at least 1/5 th of the esr zero frequency. next determine the desired crossover frequency as 1/5 th of the lower of the esr zero f esrz , the right-half-plane zero f rhpz or the switching frequency f sw . the crossover frequency equation is: ? ? ? ? ? ? ?? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? out load cs load top comp c cr r r r r f ? 2 1 11 , where f c is the crossover frequency, r top is the top side voltage divider resistor (from the output voltage to fb), r comp is the resistor of the series rc compensation network. rearrangi ng the factors of this equation yields the solution for r comp as: out c cs top comp c f rr r ? ? ? ? ?? ? 21 1 . these equations are accurate if the compensati on zero (formed by the compensation resistor r comp and the compensation capacitor c comp ) happens at a lower frequency than crossover. therefore the next step is to choose the compensation capacitor such that the compensation zero is 1/5 th of the crossover frequency, or: comp comp c compz cr f f ? 2 1 5 . solving for c comp : c comp comp fr c ? 2 5 . page 20 of 22 ? atmel inc., 2011. all rights reserved. place the mosfet and rectifier close together and as close to the output capacitor(s) as possible to reduce circuit board radiated emissions. l oop c ompensation use a series rc network from comp to fb to compensate the msl3040/41 regulation loop ( figure 3 on page 12). the regul ation loop dynamics are sensitive to output capacitor and inductor values. to begin, determine the right-half-plane zero frequency: l r v v f load out in rhpz ? 2 2 , where r load is the minimum equivalent load resistor, or )( maxout out load i v r ? . the output capacitance and type of capacitor affect the re gulation loop and method of compensation. in the case of ceramic capacitors the zero caused by the equivalent series re sistance (esr) is at such a high frequency that it is not of consequence. in the case of electrolytic or tantalum capa citors the esr is significant, so must be considered when compensating the regulation loop. determine the esr zero frequency by the equation: out esrz cesr f ?? ? ? 2 1 where c out is the value of the output capacitor, and esr is the equivalent series resistance of the output capacitor. assure that the loop crossover frequency is at least 1/5 th of the esr zero frequency. next determine the desired crossover frequency as 1/5 th of the lower of the esr zero f esrz , the right-half-plane zero f rhpz or the switching frequency f sw . the crossover frequency equation is: ? ? ? ? ? ? ?? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? out load cs load top comp c cr r r r r f ? 2 1 11 , where f c is the crossover frequency, r top is the top side voltage divider resistor (from the output voltage to fb), r comp is the resistor of the series rc compensation network. rearrangi ng the factors of this equation yields the solution for r comp as: out c cs top comp c f rr r ? ? ? ? ?? ? 21 1 . these equations are accurate if the compensati on zero (formed by the compensation resistor r comp and the compensation capacitor c comp ) happens at a lower frequency than crossover. therefore the next step is to choose the compensation capacitor such that the compensation zero is 1/5 th of the crossover frequency, or: comp comp c compz cr f f ? 2 1 5 . solving for c comp : c comp comp fr c ? 2 5 . page 20 of 22 ? atmel inc., 2011. all rights reserved. = x atmel MSL3080 datasheet 8 string 60ma led driver with integrated boost controller free datasheet http:///
22 next determine the desired crossover frequency as 1/5th of the lower of the esr zero f esrz , the right-half-plane zero f rhpz or the switching frequency f sw . the crossover frequency equation is: where f c is the crossover frequency, r top is the top side voltage divider resistor (from the output voltage to fb), r comp is the resistor of the series rc compensation network. rearranging the factors of this equation yields the solution for r comp as: these equations are accurate if the compensation zero (formed by the compensation resistor r comp and the compensation capacitor c comp ) happens at a lower frequency than crossover. therefore the next step is to choose the compensation capacitor such that the compensation zero is 1/5th of the crossover frequency, or: solving for c comp : example: as an example, set the maximum (un-optimized) output voltage to 39v, using voltage divider as follows: r top = 49.9k r bottom = 3.40k let the load current be 800ma maximum, use 10uh inductor, a 20f output capacitor, a 12v input voltage, a 12m r cs , and the switching frequency is 625khz. set the crossover frequency to 1/5th f rhpz : next calculate the compensation resistor value to achieve the 15khz crossover frequency, or then calculate the compensation capacitor, c comp , to set the compensation zero to 1/5th of the crossover frequency, or 3khz when laying out the circuit board, place the voltage divider resistors and compensation resistor/capacitors as close to the msl3040/41 as possible and minimize trace lengths connected to comp and fb. place the mosfet and rectifier close together and as close to the output capacitor(s) as possible to reduce circuit board radiated emissions. l oop c ompensation use a series rc network from comp to fb to compensate the msl3040/41 regulation loop ( figure 3 on page 12). the regul ation loop dynamics are sensitive to output capacitor and inductor values. to begin, determine the right-half-plane zero frequency: l r v v f load out in rhpz ? 2 2 , where r load is the minimum equivalent load resistor, or )( maxout out load i v r ? . the output capacitance and type of capacitor affect the re gulation loop and method of compensation. in the case of ceramic capacitors the zero caused by the equivalent series re sistance (esr) is at such a high frequency that it is not of consequence. in the case of electrolytic or tantalum capa citors the esr is significant, so must be considered when compensating the regulation loop. determine the esr zero frequency by the equation: out esrz cesr f ?? ? ? 2 1 where c out is the value of the output capacitor, and esr is the equivalent series resistance of the output capacitor. assure that the loop crossover frequency is at least 1/5 th of the esr zero frequency. next determine the desired crossover frequency as 1/5 th of the lower of the esr zero f esrz , the right-half-plane zero f rhpz or the switching frequency f sw . the crossover frequency equation is: ? ? ? ? ? ? ?? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? out load cs load top comp c cr r r r r f ? 2 1 11 , where f c is the crossover frequency, r top is the top side voltage divider resistor (from the output voltage to fb), r comp is the resistor of the series rc compensation network. rearrangi ng the factors of this equation yields the solution for r comp as: out c cs top comp c f rr r ? ? ? ? ?? ? 21 1 . these equations are accurate if the compensati on zero (formed by the compensation resistor r comp and the compensation capacitor c comp ) happens at a lower frequency than crossover. therefore the next step is to choose the compensation capacitor such that the compensation zero is 1/5 th of the crossover frequency, or: comp comp c compz cr f f ? 2 1 5 . solving for c comp : c comp comp fr c ? 2 5 . page 20 of 22 ? atmel inc., 2011. all rights reserved. place the mosfet and rectifier close together and as close to the output capacitor(s) as possible to reduce circuit board radiated emissions. l oop c ompensation use a series rc network from comp to fb to compensate the msl3040/41 regulation loop ( figure 3 on page 12). the regul ation loop dynamics are sensitive to output capacitor and inductor values. to begin, determine the right-half-plane zero frequency: l r v v f load out in rhpz ? 2 2 , where r load is the minimum equivalent load resistor, or )( maxout out load i v r ? . the output capacitance and type of capacitor affect the re gulation loop and method of compensation. in the case of ceramic capacitors the zero caused by the equivalent series re sistance (esr) is at such a high frequency that it is not of consequence. in the case of electrolytic or tantalum capa citors the esr is significant, so must be considered when compensating the regulation loop. determine the esr zero frequency by the equation: out esrz cesr f ?? ? ? 2 1 where c out is the value of the output capacitor, and esr is the equivalent series resistance of the output capacitor. assure that the loop crossover frequency is at least 1/5 th of the esr zero frequency. next determine the desired crossover frequency as 1/5 th of the lower of the esr zero f esrz , the right-half-plane zero f rhpz or the switching frequency f sw . the crossover frequency equation is: ? ? ? ? ? ? ?? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? out load cs load top comp c cr r r r r f ? 2 1 11 , where f c is the crossover frequency, r top is the top side voltage divider resistor (from the output voltage to fb), r comp is the resistor of the series rc compensation network. rearrangi ng the factors of this equation yields the solution for r comp as: out c cs top comp c f rr r ? ? ? ? ?? ? 21 1 . these equations are accurate if the compensati on zero (formed by the compensation resistor r comp and the compensation capacitor c comp ) happens at a lower frequency than crossover. therefore the next step is to choose the compensation capacitor such that the compensation zero is 1/5 th of the crossover frequency, or: comp comp c compz cr f f ? 2 1 5 . solving for c comp : c comp comp fr c ? 2 5 . page 20 of 22 ? atmel inc., 2011. all rights reserved. place the mosfet and rectifier close together and as close to the output capacitor(s) as possible to reduce circuit board radiated emissions. l oop c ompensation use a series rc network from comp to fb to compensate the msl3040/41 regulation loop ( figure 3 on page 12). the regul ation loop dynamics are sensitive to output capacitor and inductor values. to begin, determine the right-half-plane zero frequency: l r v v f load out in rhpz ? 2 2 , where r load is the minimum equivalent load resistor, or )( maxout out load i v r ? . the output capacitance and type of capacitor affect the re gulation loop and method of compensation. in the case of ceramic capacitors the zero caused by the equivalent series re sistance (esr) is at such a high frequency that it is not of consequence. in the case of electrolytic or tantalum capa citors the esr is significant, so must be considered when compensating the regulation loop. determine the esr zero frequency by the equation: out esrz cesr f ?? ? ? 2 1 where c out is the value of the output capacitor, and esr is the equivalent series resistance of the output capacitor. assure that the loop crossover frequency is at least 1/5 th of the esr zero frequency. next determine the desired crossover frequency as 1/5 th of the lower of the esr zero f esrz , the right-half-plane zero f rhpz or the switching frequency f sw . the crossover frequency equation is: ? ? ? ? ? ? ?? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? out load cs load top comp c cr r r r r f ? 2 1 11 , where f c is the crossover frequency, r top is the top side voltage divider resistor (from the output voltage to fb), r comp is the resistor of the series rc compensation network. rearrangi ng the factors of this equation yields the solution for r comp as: out c cs top comp c f rr r ? ? ? ? ?? ? 21 1 . these equations are accurate if the compensati on zero (formed by the compensation resistor r comp and the compensation capacitor c comp ) happens at a lower frequency than crossover. therefore the next step is to choose the compensation capacitor such that the compensation zero is 1/5 th of the crossover frequency, or: comp comp c compz cr f f ? 2 1 5 . solving for c comp : c comp comp fr c ? 2 5 . page 20 of 22 ? atmel inc., 2011. all rights reserved. place the mosfet and rectifier close together and as close to the output capacitor(s) as possible to reduce circuit board radiated emissions. l oop c ompensation use a series rc network from comp to fb to compensate the msl3040/41 regulation loop ( figure 3 on page 12). the regul ation loop dynamics are sensitive to output capacitor and inductor values. to begin, determine the right-half-plane zero frequency: l r v v f load out in rhpz ? 2 2 , where r load is the minimum equivalent load resistor, or )( maxout out load i v r ? . the output capacitance and type of capacitor affect the re gulation loop and method of compensation. in the case of ceramic capacitors the zero caused by the equivalent series re sistance (esr) is at such a high frequency that it is not of consequence. in the case of electrolytic or tantalum capa citors the esr is significant, so must be considered when compensating the regulation loop. determine the esr zero frequency by the equation: out esrz cesr f ?? ? ? 2 1 where c out is the value of the output capacitor, and esr is the equivalent series resistance of the output capacitor. assure that the loop crossover frequency is at least 1/5 th of the esr zero frequency. next determine the desired crossover frequency as 1/5 th of the lower of the esr zero f esrz , the right-half-plane zero f rhpz or the switching frequency f sw . the crossover frequency equation is: ? ? ? ? ? ? ?? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? out load cs load top comp c cr r r r r f ? 2 1 11 , where f c is the crossover frequency, r top is the top side voltage divider resistor (from the output voltage to fb), r comp is the resistor of the series rc compensation network. rearrangi ng the factors of this equation yields the solution for r comp as: out c cs top comp c f rr r ? ? ? ? ?? ? 21 1 . these equations are accurate if the compensati on zero (formed by the compensation resistor r comp and the compensation capacitor c comp ) happens at a lower frequency than crossover. therefore the next step is to choose the compensation capacitor such that the compensation zero is 1/5 th of the crossover frequency, or: comp comp c compz cr f f ? 2 1 5 . solving for c comp : c comp comp fr c ? 2 5 . page 20 of 22 ? atmel inc., 2011. all rights reserved. example: as an example, set the maximum (un-optimized) out put voltage to 39v, using voltage divider as follows: r top = 49.9k r bottom = 3.40k let the load current be 800ma maximum, use 10uh inductor, a 20 ? f output capacitor, a 12v input voltage, a 12m ? r cs , and the switching frequency is 625khz. ?? ?? 75.48 8.0 39 a v i v r load out load ?? khz l r v v f load out in rhpz 73 10102 75.48 39 12 2 6 2 2 ? ? ? ? ? ? ? ?? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? set the crossover frequency to 1/5 th f rhpz : khz f f rhpz c 6 .1 4 5 ?? . next calculate the compensation resistor value to achieve the 15khz crossover frequency, or ? ? ? ? ? ? ? ?? ? ? ? ?? kf k k c f rr r out c cs top comp 9.2520152025.119.49 21 1 ? ? ? then calculate the compensation capacitor, c comp , to set the compensation zero to 1/5 th of the crossover frequency, or 3khz nf kk fr c compz comp comp 1.2 3 2 52 1 2 1 ? ?? ? ?? ? ? ? . when laying out the circuit board, place the voltage divider resi stors and compensation resistor /capacitors as close to the msl3040/41 as possible and minimize trace lengths connected to comp and fb. led dimming control e xternal and i 2 c c ontrol of led brightness control msl3040 led brightness using puls e width modulation (pwm) with a pwm signal applied to the external pwm input. the pwm dimming signals (outputs) take the frequency and duty cycle of the input sign al but are staggered in time so that they start at evenly spaced intervals relative to the pwm input signal. when one or more strings are disabled by fault response, the stagger delays automatically re -calculate for the remaining enabled strings. the msl3041 accepts two input signals, sync and pwm. sync provides the frequency information for the pwm dimming, and pwm provides the duty cycle information. t he led pwm dimming signals are staggered based on the frequency at sync. for all drivers, use pwm and sync inputs frequency between 20hz and 50khz and duty cycle between 0% and 100% (avoid duty cycles above 99.97% and less than 100%). additionally, internal registers accessed using the i 2 c compatible serial interface allow control of the pwm dimming frequency and duty cycle. for programming details see the msl3040/41/50/60/80/86/ 87/88 programming guide. page 21 of 22 ? atmel inc., 2011. all rights reserved. example: as an example, set the maximum (un-optimized) out put voltage to 39v, using voltage divider as follows: r top = 49.9k r bottom = 3.40k let the load current be 800ma maximum, use 10uh inductor, a 20 ? f output capacitor, a 12v input voltage, a 12m ? r cs , and the switching frequency is 625khz. ?? ?? 75.48 8.0 39 a v i v r load out load ?? khz l r v v f load out in rhpz 73 10102 75.48 39 12 2 6 2 2 ? ? ? ? ? ? ? ?? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? set the crossover frequency to 1/5 th f rhpz : khz f f rhpz c 6 .1 4 5 ?? . next calculate the compensation resistor value to achieve the 15khz crossover frequency, or ? ? ? ? ? ? ? ?? ? ? ? ?? kf k k c f rr r out c cs top comp 9.2520152025.119.49 21 1 ? ? ? then calculate the compensation capacitor, c comp , to set the compensation zero to 1/5 th of the crossover frequency, or 3khz nf kk fr c compz comp comp 1.2 3 2 52 1 2 1 ? ?? ? ?? ? ? ? . when laying out the circuit board, place the voltage divider resi stors and compensation resistor /capacitors as close to the msl3040/41 as possible and minimize trace lengths connected to comp and fb. led dimming control e xternal and i 2 c c ontrol of led brightness control msl3040 led brightness using puls e width modulation (pwm) with a pwm signal applied to the external pwm input. the pwm dimming signals (outputs) take the frequency and duty cycle of the input sign al but are staggered in time so that they start at evenly spaced intervals relative to the pwm input signal. when one or more strings are disabled by fault response, the stagger delays automatically re -calculate for the remaining enabled strings. the msl3041 accepts two input signals, sync and pwm. sync provides the frequency information for the pwm dimming, and pwm provides the duty cycle information. t he led pwm dimming signals are staggered based on the frequency at sync. for all drivers, use pwm and sync inputs frequency between 20hz and 50khz and duty cycle between 0% and 100% (avoid duty cycles above 99.97% and less than 100%). additionally, internal registers accessed using the i 2 c compatible serial interface allow control of the pwm dimming frequency and duty cycle. for programming details see the msl3040/41/50/60/80/86/ 87/88 programming guide. page 21 of 22 ? atmel inc., 2011. all rights reserved. example: as an example, set the maximum (un-optimized) out put voltage to 39v, using voltage divider as follows: r top = 49.9k r bottom = 3.40k let the load current be 800ma maximum, use 10uh inductor, a 20 ? f output capacitor, a 12v input voltage, a 12m ? r cs , and the switching frequency is 625khz. ?? ?? 75.48 8.0 39 a v i v r load out load ?? khz l r v v f load out in rhpz 73 10102 75.48 39 12 2 6 2 2 ? ? ? ? ? ? ? ?? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? set the crossover frequency to 1/5 th f rhpz : khz f f rhpz c 6 .1 4 5 ?? . next calculate the compensation resistor value to achieve the 15khz crossover frequency, or ? ? ? ? ? ? ? ?? ? ? ? ?? kf k k c f rr r out c cs top comp 9.2520152025.119.49 21 1 ? ? ? then calculate the compensation capacitor, c comp , to set the compensation zero to 1/5 th of the crossover frequency, or 3khz nf kk fr c compz comp comp 1.2 3 2 52 1 2 1 ? ?? ? ?? ? ? ? . when laying out the circuit board, place the voltage divider resi stors and compensation resistor /capacitors as close to the msl3040/41 as possible and minimize trace lengths connected to comp and fb. led dimming control e xternal and i 2 c c ontrol of led brightness control msl3040 led brightness using puls e width modulation (pwm) with a pwm signal applied to the external pwm input. the pwm dimming signals (outputs) take the frequency and duty cycle of the input sign al but are staggered in time so that they start at evenly spaced intervals relative to the pwm input signal. when one or more strings are disabled by fault response, the stagger delays automatically re -calculate for the remaining enabled strings. the msl3041 accepts two input signals, sync and pwm. sync provides the frequency information for the pwm dimming, and pwm provides the duty cycle information. t he led pwm dimming signals are staggered based on the frequency at sync. for all drivers, use pwm and sync inputs frequency between 20hz and 50khz and duty cycle between 0% and 100% (avoid duty cycles above 99.97% and less than 100%). additionally, internal registers accessed using the i 2 c compatible serial interface allow control of the pwm dimming frequency and duty cycle. for programming details see the msl3040/41/50/60/80/86/ 87/88 programming guide. page 21 of 22 ? atmel inc., 2011. all rights reserved. example: as an example, set the maximum (un-optimized) out put voltage to 39v, using voltage divider as follows: r top = 49.9k r bottom = 3.40k let the load current be 800ma maximum, use 10uh inductor, a 20 ? f output capacitor, a 12v input voltage, a 12m ? r cs , and the switching frequency is 625khz. ?? ?? 75.48 8.0 39 a v i v r load out load ?? khz l r v v f load out in rhpz 73 10102 75.48 39 12 2 6 2 2 ? ? ? ? ? ? ? ?? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? set the crossover frequency to 1/5 th f rhpz : khz f f rhpz c 6 .1 4 5 ?? . next calculate the compensation resistor value to achieve the 15khz crossover frequency, or ? ? ? ? ? ? ? ?? ? ? ? ?? kf k k c f rr r out c cs top comp 9.2520152025.119.49 21 1 ? ? ? then calculate the compensation capacitor, c comp , to set the compensation zero to 1/5 th of the crossover frequency, or 3khz nf kk fr c compz comp comp 1.2 3 2 52 1 2 1 ? ?? ? ?? ? ? ? . when laying out the circuit board, place the voltage divider resi stors and compensation resistor /capacitors as close to the msl3040/41 as possible and minimize trace lengths connected to comp and fb. led dimming control e xternal and i 2 c c ontrol of led brightness control msl3040 led brightness using puls e width modulation (pwm) with a pwm signal applied to the external pwm input. the pwm dimming signals (outputs) take the frequency and duty cycle of the input sign al but are staggered in time so that they start at evenly spaced intervals relative to the pwm input signal. when one or more strings are disabled by fault response, the stagger delays automatically re -calculate for the remaining enabled strings. the msl3041 accepts two input signals, sync and pwm. sync provides the frequency information for the pwm dimming, and pwm provides the duty cycle information. t he led pwm dimming signals are staggered based on the frequency at sync. for all drivers, use pwm and sync inputs frequency between 20hz and 50khz and duty cycle between 0% and 100% (avoid duty cycles above 99.97% and less than 100%). additionally, internal registers accessed using the i 2 c compatible serial interface allow control of the pwm dimming frequency and duty cycle. for programming details see the msl3040/41/50/60/80/86/ 87/88 programming guide. page 21 of 22 ? atmel inc., 2011. all rights reserved. = x = x x = x atmel MSL3080 datasheet 8 string 60ma led driver with integrated boost controller free datasheet http:///
23 10.0 led dimming control 10.1 external and i 2 c control of led brightness control led brightness using pulse width modulation (pwm) with a pwm signal applied to the external pwm input. the led pwm dimming occurs at the same frequency and duty cycle as the input signal. for all drivers, use pwm input frequency between 20hz and 50khz and duty cycle between 0% and 100%. additionally, internal registers, accessed using the i2c compatible serial interface, allow control of the pwm dimming frequency and duty cycle. for programming details see the msl3040/50/60/80/86/87/88 programming guide . 11.0 ordering information table 11.1 ordering information part description pkg MSL3080-iu 8-ch led driver with integrated boost controller and resistor based led short circuit threshold setting, with single pwm input. 24 pin 4 x 4 x 0.75mm vqfn ? 2012 atmel corporation. all rights reserved. / rev.: MSL3080 datasheet dbie-20120814 atmel?, logo and combinations thereof, and others are registered trademarks or trademarks of atmel corporation or its subsidiaries. other terms and product names may be trademarks of others. disclaimer: the information in this document is provided in connection with atmel products. no license, express or implied, by estoppel or otherwise, to any intellectual property right is granted by this document or in connection with the sale of atmel products. except as set forth in the atmel terms and conditions of sales located on the atmel website, atmel assumes no liability whatsoever and disclaims any express, implied or statutory warranty relating to its products including, but not limited to, the implied warranty of merchantability, fitness for a particular purpose, or non-infringement. in no event shall atmel be liable for any direct, indirect, consequential, punitive, special or incidental damages (including, without limitation, damages for loss and profits, business interruption, or loss of information) arising out of the use or inability to use this document, even if atmel has been advised of the possibility of such damages. atmel makes no representations or warranties with respect to the accuracy or completeness of the contents of this document and reserves the right to make changes to specifcations and products descriptions at any time without notice. atmel does not make any commitment to update the information contained herein. unless specifcally provided otherwise, atmel products are not suitable for, and shall not be used in, automotive applications. atmel products are not intended, authorized, or warranted for use as components in applications intended to support or sustain life. atmel corporation 2325 orchard parkway san jose, ca 95131 usa tel: (+1)(408) 441-0311 fax: (+1)(408) 487-2600 www.atmel.com atmel asia limited unit 01-5 & 16, 19f bea tower, millennium city 5 418 kwun tong road kwun tong, kowloon hong kong tel: (+852) 2245-6100 fax: (+852) 2722-1369 atmel munich gmbh business campus parkring 4 d-85748 garching b. munich germany tel: (+49) 89-31970-0 fax: (+49) 89-3194621 atmel japan 9f, tonetsu shinkawa bldg. 1-24-8 shinkawa chuo-ku, tokyo 104-0033 japan tel: (+81)(3) 3523-3551 fax: (+81)(3) 3523-7581 atmel MSL3080 datasheet 8 string 60ma led driver with integrated boost controller free datasheet http:///

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