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lt3495/lt3495b/ lt3495-1/lt3495b-1 1 3495b1b1fa typical application features applications description 650ma/350ma micropower low noise boost converter with output disconnect the lt ? 3495/lt3495b/lt3495-1/lt3495b-1 are low noise boost converters with integrated power switch, feedback resistor and output disconnect circuitry. the parts control power delivery by varying both the peak inductor current and switch off-time. this novel* control scheme results in low output voltage ripple as well as high ef? ciency over a wide load range. for the lt3495/lt3495-1, the off-time of the switch is not allowed to exceed a ? xed level, guaranteeing the switching frequency stays above the audio band for the entire load range. the parts feature a high performance npn power switch with a 650ma and 350ma current limit for the lt3495/lt3495b and lt3495-1/lt3495b-1 respectively. the quiescent current is a low 60a, which is further reduced to less than 0.1a in shutdown. the internal disconnect circuitry allows the output voltage to be isolated from the input during shut- down. an auxiliary reference input (ctrl pin) overrides the internal 1.235v feedback reference with any lower value allowing full control of the output voltage during operation. the lt3495 series are available in a tiny 10-lead 3mm 2mm dfn package. oled power supply from one li-ion cell n low quiescent current 60a in active mode 0.1a in shutdown mode n low noise control scheme (switching frequency always stays above audible range for lt3495/-1) n integrated power npn: 650ma current limit (lt3495/b) 350ma current limit (lt3495-1/b-1) n integrated output disconnect n integrated output dimming n wide input range: 2.5v to 16v n wide output range: up to 40v n integrated feedback resistor n tiny 10-lead 3mm 2mm dfn package n oled power n low noise power n mp3 player output voltage ripple vs load current ef? ciency vs load current l , lt, ltc and ltm are registered trademarks of linear technology corporation. all other trademarks are the property of their respective owners. *patent pending. load current (ma) 0.1 v out peak-to-peak ripple (mv) 50 40 20 30 10 0 1 3495 ta01b 100 10 1.0f 0603 capacitor at v out 2.2f 1206 capacitor at v out sw cap v cc shdn ctrl v out fb gnd 909k 3495 ta01a lt3495 4.7f 1f 10h 2.2f one li-ion cell v out 16v 70ma load current (ma) efficiency (%) power loss (mw) 3495 ta01c 90 80 50 60 70 40 400 320 80 160 240 0 0.1 10 100 1 v in = 3.6v load from cap load from v out
lt3495/lt3495b/ lt3495-1/lt3495b-1 2 3495b1b1fa pin configuration absolute maximum ratings v cc voltage ...............................................................16v sw voltage ...............................................................40v cap voltage ..............................................................40v v out voltage .............................................................40v shdn voltage ...........................................................10v ctrl voltage ............................................................10v fb voltage ................................................................2.5v maximum junction temperature........................... 125c operating temperature range (note 2).. C40c to 125c storage temperature range ................... C65c to 150c (note 1) top view 11 ddb package 10-lead (3mm 2mm) plastic dfn gnd gnd v cc ctrl shdn sw cap cap v out fb 6 8 7 9 10 5 4 2 3 1 t jmax = 125c, ja = 76c/w exposed pad (pin 11) is gnd, must be soldered to pcb order information lead free finish tape and reel part marking package description temperature range lt3495eddb#pbf lt3495eddb#trpbf ldss 10-lead (3mm 2mm) plastic dfn C40c to 125c lt3495eddb-1#pbf lt3495eddb-1#trpbf ldsv 10-lead (3mm 2mm) plastic dfn C40c to 125c lt3495beddb#pbf lt3495beddb#trpbf ldst 10-lead (3mm 2mm) plastic dfn C40c to 125c lt3495beddb-1#pbf lt3495beddb-1#trpbf ldsw 10-lead (3mm 2mm) plastic dfn C40c to 125c consult ltc marketing for parts speci? ed with wider operating temperature ranges. consult ltc marketing for information on non-standard lead based ? nish parts. for more information on lead free part marking, go to: http://www.linear.com/leadfree/ for more information on tape and reel speci? cations, go to: http://www.linear.com/tapeandreel/ parameter conditions min typ max units minimum operating voltage 2.2 2.5 v maximum operating voltage 16 v fb voltage v ctrl = 3v, (note 3) l 1.220 1.235 1.255 v fb voltage line regulation 0.03 %/v fb resistor fb voltage = 1.235v l 74.7 76 77 k quiescent current not switching 60 70 a quiescent current in shutdown v shdn = 0v, v cc = 3v 0 1 a minimum switch-off time after start-up (note 4) during start-up (note 4) 200 500 ns ns maximum switch-off time lt3495/lt3495-1, v fb = 1.5v l 17 26 35 s maximum switch-on time 10 s switch current limit lt3495/lt3495b l 550 650 780 ma the l denotes the speci? cations which apply over the full operating temperature range, otherwise speci? cations are at t a = 25c. v cc = 3v, v shdn = v cc , unless otherwise noted. (note 2) electrical characteristics
lt3495/lt3495b/ lt3495-1/lt3495b-1 3 3495b1b1fa note 1: stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. exposure to any absolute maximum rating condition for extended periods may affect device reliability and lifetime. note 2: the lt3495/lt3495b/lt3495-1/lt3495b-1 are guaranteed to meet performance speci? cations from 0c to 125c junction temperature. speci? cations over the C40c to 125c operating junction temperature range are assured by design, characterization and correlation with statistical process controls. electrical characteristics the l denotes the speci? cations which apply over the full operating temperature range, otherwise speci? cations are at t a = 25c. v cc = 3v, v shdn = v cc , unless otherwise noted. (note 2) parameter conditions min typ max units switch current limit lt3495-1/lt3495b-1 l 275 350 450 ma switch v cesat lt3495/lt3495b, i sw = 400ma lt3495-1/lt3495b-1, i sw = 200ma 200 125 mv mv switch leakage current v sw = 5v 0.01 1 a pmos disconnect current limit after start-up during start-up 250 110 370 150 450 190 ma ma pmos disconnect v cap C v out i out = 50ma, v cap = 15v 150 mv v cap C v out clamp voltage 8.7 v shdn input voltage high 1.5 v shdn input voltage low 0.3 v shdn pin bias current v shdn = 3v v shdn = 0v 5.3 0 8a a ctrl pin bias current v ctrl = 0.5v, current flows out of pin l 20 100 na ctrl to fb offset v ctrl = 0.5v 6 14 mv maximum shunt current lt3495/lt3495-1, v fb = 1.5v 230 a note 3: internal reference voltage is determined by ? nding v fb voltage level which causes quiescent current to increase 150a above not switching level. note 4: if ctrl is overriding the internal reference, start-up mode occurs when v fb is less then half the voltage on ctrl. if ctrl is not overriding the internal reference, start-up mode occurs when v fb is less then half the voltage of the internal reference. typical performance characteristics t a = 25c unless otherwise noted. switching frequency vs load current load regulation v out vs ctrl voltage load current (ma) 0 switching frequency (khz) 1000 800 400 200 600 0 80 40 3495 g01 120 60 20 100 v cc = 3.6v v out = 16v figure 7 circuit load current (ma) 0 v out voltage change (%) 1.5 1.0 0.0 C0.5 C1.0 0.5 C1.5 80 40 3495 g02 120 60 20 100 v cc = 3.6v v out = 16v figure 7 circuit ctrl voltage (v) 0 v out voltage (v) 18 15 9 6 3 12 0 1.2 0.6 3495 g03 1.5 0.9 0.3 figure 7 circuit
lt3495/lt3495b/ lt3495-1/lt3495b-1 4 3495b1b1fa shdn current vs shdn voltage peak inductor current vs temperature (lt3495) peak inductor current vs temperature (lt3495-1) typical performance characteristics output voltage vs temperature minimum switching frequency quiescent current - not switching quiescent current vs temperature sw saturation voltage vs switch current (lt3495) sw saturation voltage vs switch current (lt3495-1) t a = 25c unless otherwise noted. temperature (c) C40 output voltage change (%) 1.00 0.75 0.25 0.00 C0.75 C0.50 C0.25 0.50 C1.00 80 0 3495 g04 125 40 v cc = 3.6v v out = 16v load = 5ma figure 7 circuit temperature (c) C40 minimum switching frequency (khz) 50 40 35 45 30 80 0 3495 g05 125 40 figure 7 circuit v cc (v) 2 quiescent current (a) 100 70 80 60 90 50 14 12 10 8 4 3495 g06 16 6 temperature (c) C40 quiescent current (a) 100 70 80 60 90 50 80 0 3495 g07 125 40 switch current (ma) 0 switch v cesat (mv) 300 100 150 50 200 250 0 600 200 100 300 3495 g08 700 400 500 switch current (ma) 0 switch v cesat (mv) 200 80 120 40 160 0 200 100 300 3495 g09 400 shdn pin voltage (v) 0 shdn pin current (a) 20 5 10 15 0 4 268 3495 g10 10 temperature (c) C40 inductor peak current (ma) 1000 700 800 900 600 40 080 3495 g11 125 v cc = 3.6v v out = 16v figure 7 circuit temperature (c) C40 inductor peak current (ma) 600 350 400 450 500 550 300 40 080 3495 g12 125 figure 9 circuit
lt3495/lt3495b/ lt3495-1/lt3495b-1 5 3495b1b1fa typical performance characteristics lt3495 switching waveform at no load lt3495 switching waveform at 10ma lt3495 switching waveform at 80ma lt3495b-1 switching waveform at no load lt3495b-1 switching waveform at 10ma lt3495b-1 switching waveform at 60ma t a = 25c unless otherwise noted. 10s/div 3495 g13 v out voltage 10mv/div ac coupled inductor current 100ma/div sw voltage 10v/div v cc = 3.6v v out = 16v 2s/div 3495 g14 v out voltage 50mv/div ac coupled inductor current 500ma/div sw voltage 10v/div v cc = 3.6v v out = 16v 500ns/div 3495 g15 v out voltage 50mv/div ac coupled inductor current 500ma/div sw voltage 10v/div v cc = 3.6v v out = 16v 20s/div 3495 g16 v out voltage 20mv/div ac coupled inductor current 100ma/div sw voltage 10v/div v cc = 5v v out = 16v 2s/div 3495 g17 v out voltage 50mv/div ac coupled inductor current 200ma/div sw voltage 10v/div v cc = 5v v out = 16v 500ns/div 3495 g18 v out voltage 50mv/div ac coupled inductor current 200ma/div sw voltage 10v/div v cc = 5v v out = 16v
lt3495/lt3495b/ lt3495-1/lt3495b-1 6 3495b1b1fa typical performance characteristics line regulation output disconnect pmos current vs cap to v out voltage difference lt3495 start-up waveforms lt3495 transient response lt3495-1 transient response v cc voltage (v) 0 output voltage change (%) 0.30 0.05 0.10 0.15 0.20 0.25 0 8 412 3495 g19 16 cap to v out voltage difference (v) 0 pmos current (ma) 600 100 0 200 300 400 500 C100 6 4 2810 3495 g20 12 after start-up in start-up in shutdown 20s/div 3495 g23 v out voltage 200mv/div ac coupled load current 20ma/div inductor current 200ma/div v cc = 3.6v v out = 16v figure 9 circuit 10ma 30ma 10ma load pulse 50s/div 3495 g21 shdn voltage 5v/div cap voltage 5v/div v out voltage 5v/div inductor current 500ma/div v cc = 3.6v v out = 16v figure 7 circuit t a = 25c unless otherwise noted. 20s/div 3495 g22 load current 20ma/div v out voltage 200mv/div ac coupled inductor current 500ma/div v cc = 3.6v v out = 16v figure 7 circuit 20ma 60ma 20ma load pulse
lt3495/lt3495b/ lt3495-1/lt3495b-1 7 3495b1b1fa block diagram pin functions gnd (pins 1, 2): ground. tie directly to local ground plane. v cc (pin 3): input supply pin. must be locally by- passed. ctrl (pin 4): dimming pin. if not used, tie ctrl to 1.5v or higher. if in use, drive ctrl below 1.235v to override the internal reference. see applications section for more information. shdn (pin 5): shutdown pin. tie to 1.5v or more to en- able chip. ground to shut down. fb (pin 6): feedback pin. minimize the metal trace area to this pin to minimize noise. reference voltage is 1.235v. there is an internal 76k resistor from the fb pin to gnd. to achieve the desired output voltage, choose r1 according to the following formula: r1 = 76 ? (v out /1.235 C 1)k v out (pin 7): drain of output disconnect pmos. place a bypass capacitor from this pin to gnd. see applications information. cap (pins 8, 9): source of output disconnect pmos. place a bypass capacitor from this pin to gnd. sw (pin 10): switch pin. this is the collector of the in- ternal npn power switch. minimize the metal trace area connected to this pin to minimize emi. exposed pad (pin 11): ground. this pin must be soldered to pcb. 10 + C + + 6 3 4 fb ctrl 76k 5 shdn v ref switch control shunt control disconnect control start-up control v cc input sw 2 gnd 1 11 gnd 8 cap 9 cap 7 v out r1 3495 bd
lt3495/lt3495b/ lt3495-1/lt3495b-1 8 3495b1b1fa operation the lt3495 series utilizes a variable peak current, variable off-time control scheme to provide high ef? ciency over a wide range of output current. the operation of the part can be better understood by referring to the block diagram. the part senses the output voltage by monitoring the voltage on the fb pin. the user sets the desired output voltage by choosing the value of the external top feedback resistor. the parts incorporate a precision 76k bottom feedback resistor. assuming that output voltage adjustment is not used (ctrl pin is tied to 1.5v or greater), the internal reference (v ref = 1.235v) sets the voltage at which fb will servo to during regulation. the switch control block senses the output of the ampli- ? er and adjusts the switching frequency as well as other parameters to achieve regulation. during the start-up of the circuit, special precautions are taken to ensure that the inductor current remains under control. for the lt3495/lt3495-1, the switching frequency is never allowed to fall below approximately 45khz. because of this, a minimum load must be present to prevent the output voltage from drifting too high. for most applications, this minimum load is automatically generated within the part via the shunt control block. the level of this current is adaptable, removing itself when not needed to improve ef? ciency at higher load levels. however when the input table 1. difference between lt3495 and lt3495b/lt3495-1/lt3495b-1 part switch current limit (ma) minimum switching frequency (khz) minimum output load requirement lt3495 650 45 required under certain conditions lt3495b 650 0 not required lt3495-1 350 45 required under certain conditions lt3495b-1 350 0 not required voltage and output voltage are close, the internal shunt current may not be large enough. under this condition, a minimum output load is required to prevent the output voltage from drifting too high. for the lt3495b/b-1, the minimum switching frequency feature is disabled and the switching frequency can be as low as zero. as a result, the output voltage will never drift high and no minimum output load is required. the lt3495 series also has a pmos output disconnect switch. the pmos switch is turned on when the part is enabled via the shdn pin. when the parts are in shutdown, the pmos switch turns off, allowing the v out node to go to ground. this type of disconnect function is often required in power supplies. the lt3495 series also sets a maximum switch on time of 10s. this feature guarantees that the parts can continue to deliver energy to the output even if the input supply impedance becomes so large that the commanded peak switch current is never reached. the difference between the lt3495/lt3495b and lt3495-1/ lt3495b-1 is the level of the current limit. lt3495/lt3495b have a typical peak current limit of 650ma while the lt3495-1/lt3495b-1 have a typical peak current limit of 350ma. the differences between the lt3495 and lt3495b/ lt3495-1/lt3495b-1 are listed in table 1.
lt3495/lt3495b/ lt3495-1/lt3495b-1 9 3495b1b1fa applications information inductor selection several inductors that work well with the lt3495/lt3495b are listed in table 2 and those for the lt3495-1/lt3495b-1 are listed in table 3. these tables are not complete, and there are many other manufacturers and devices that can be used. consult each manufacturer for more detailed information and for their entire selection of related parts, as many different sizes and shapes are available. inductors with a value of 3.3h or higher are recommended for most lt3495 series designs. inductors with low core losses and small dcr (copper wire resistance) are good choices for lt3495 series applications. for full output power, the inductor should have a saturation current rating higher than the peak inductor current. the peak inductor current can be calculated as: i pk = i limit + v in ? 200 ? 10 ?9 l amps where i limit is 0.65a and 0.35a for lt3495/lt3495b and lt3495-1/lt3495b-1 respectively. l is the inductance value in henrys and v in is the input voltage to the boost circuit. table 2. recommended inductors for lt3495/lt3495b part l (h) dcr (m) s ize (mm) vendor lps4018-103ml mss5131-103mlc lps3015-472mlc lps3015-682mlc 10 10 4.7 6.8 200 83 200 300 4.4 4.4 1.7 5.1 5.1 3.1 3.0 3.0 1.5 3.0 3.0 1.5 coilcraft www.coilcraft.com lqh43cn4r7m03 4.7 150 4.5 3.2 2.8 murata www.murata.com cr32-6r8 6.8 202 4.1 3.7 3.0 sumida www.sumida.com 744031004 4.7 105 3.8 3.8 1.7 wurth elektronik www.weonline.com capacitor selection the small size and low esr of ceramic capacitors makes them suitable for most lt3495 series applications. x5r and x7r types are recommended because they retain their capacitance over wider voltage and temperature ranges than other types such as y5v or z5u. a 4.7f input capacitor and a 1f to 10f output capacitor are suf? cient for most applications. always use a capacitor with a suf? cient voltage rating. many capacitors rated at 1f to 10f, particularly 0603 case sizes, have greatly reduced capacitance when bias voltages are applied. be sure to check actual capacitance at the desired output voltage. generally a 0805 or 1206 size capacitor will be adequate. a 2.2f capacitor placed on the cap node is recommended to ? lter the inductor current while a 1f to 10f capacitor placed on the v out node will give excellent transient response and stability. table 4 shows a list of several capacitor manufacturers. consult the manufac- turers for more detailed information and for their entire selection of related parts. table 3. recommended inductors for lt3495-1/lt3495b-1 part l (h) dcr (m) size (mm) vendor lpo4815-472mlc lpo4815-682mlc lpo4815-103mlc lps3008-472mlc lps3008-682mlc lps3008-103mlc 4.7 6.8 10 4.7 6.8 10 150 180 230 350 500 650 4.8 4.8 1.5 4.8 4.8 1.5 4.8 4.8 1.5 3.0 3.0 0.8 3.0 3.0 0.8 3.0 3.0 0.8 coilcraft www.coilcraft.com lqh32cn4r7m53 lqh32cn100k33 4.7 10 150 300 3.2 2.5 1.6 3.2 2.5 2.0 murata www.murata.com cdh28d09/s-6r2 6.2 369 3.3 3.0 1.0 sumida www.sumida.com 744030004 4.7 290 3.5 3.3 1.0 wurth elektronik www.weonline.com table 4. recommended ceramic capacitor manufacturers manufacturer phone website taiyo yuden (408) 573-4150 www.t-yuden.com avx (843) 448-9411 www.avxcorp.com murata (814) 237-1431 www.murata.com kemet (408) 986-0424 www.kemet.com tdk (847) 803-6100 www.tdk.com diode selection schottky diodes, with their low forward voltage drops and fast switching speeds, are recommended for use with the lt3495 series. the diodes inc. b0540ws-7 is a very good choice. this diode is rated to handle an average forward current of 0.5a with 40v reverse breakdown.
lt3495/lt3495b/ lt3495-1/lt3495b-1 10 3495b1b1fa applications information figure 2. feedback connection using the cap pin or the v out pin sw cap v cc shdn ctrl v out fb gnd r1 lt3495 c1 c3 v out sw cap v cc shdn ctrl v out fb gnd r1 3495 f02 lt3495 c1 sw cap v cc shdn ctrl v out fb gnd 3495 f03 lt3495 c1 i load figure 1. ctrl to fb transfer curve figure 3. improved ef? ciency connection setting output voltage and the auxiliary reference input the lt3495 series is equipped with both an internal 1.235v reference and an auxiliary reference input. this allows the user to select between using the built-in refer- ence and supplying an external reference voltage. the voltage at the ctrl pin can be adjusted while the chip is operating to alter the output voltage for purposes such as display dimming or contrast adjustment. to use the internal 1.235v reference, the ctrl pin must be held higher than 1.5v. when the ctrl pin is held between 0v and 1.235v, the parts will regulate the output such that the fb pin voltage is nearly equal to the ctrl pin voltage. at ctrl voltages close to 1.235v, a soft transition occurs between the ctrl pin and the internal reference. figure 1 shows this behavior. to set the maximum output voltage, select the values of r1 according to the following equation: r1 = 76 ? v out 1.235 C1 k when ctrl is used to override the internal reference, the output voltage can be lowered from the maximum value down to nearly the input voltage level. if the volt- age source driving the ctrl pin is located at a distance to the lt3495, a small 0.1f capacitor may be needed to bypass the pin locally. choosing a feedback node the single feedback resistor may be connected to the v out pin or to the cap pin (see figure 2). regulating the v out pin eliminates the output offset resulting from the voltage drop across the output disconnect pmos. regu- lating the cap pin does not compensate for the voltage drop across the output disconnect, resulting in an output voltage v out that is slightly lower than the voltage set by the resistor divider. under most conditions, it is advised that the feedback resistor be tied to the v out pin. connecting the load to the cap node the ef? ciency of the converter can be improved by con- necting the load to the cap pin instead of the v out pin. the power loss in the pmos disconnect circuit is then made negligible. by connecting the feedback resistor to the v out pin, no quiescent current will be consumed in the feedback resistor string during shutdown since the pmos transistor will be open (see figure 3). the disadvantage of this method is that the cap node cannot go to ground during shutdown, but will be limited to around a diode drop below v cc . loads connected to the part should only sink current. never force external power supplies onto the cap or v out pins. ctrl voltage (v) 0 fb voltage (v) 1.5 1.2 0.6 0.9 0.3 0 0.9 3495 f01 1.5 0.6 0.3 1.2
lt3495/lt3495b/ lt3495-1/lt3495b-1 11 3495b1b1fa applications information maximum output load current the maximum output current of a particular lt3495 series circuit is a function of several circuit variables. the fol- lowing method can be helpful in predicting the maximum load current for a given circuit: step 1: calculate the peak inductor current: i pk = i limit + v in ? 200 ? 10 ?9 l amps where i limit is 0.65a and 0.35a for lt3495/lt3495b and lt3495-1/lt3495b-1 respectively. l is the inductance value in henrys and v in is the input voltage to the boost circuit. step 2: calculate the inductor ripple current: i ripple = v out + 1? v in () ? 200 ? 10 ?9 l amps where v out is the desired output voltage. if the inductor ripple current is greater than the peak current, then the circuit will only operate in discontinuous conduction mode. the inductor value should be increased so that i ripple < i pk . an application circuit can be designed to operate only in discontinuous mode, but the output current capability will be reduced. step 3: calculate the average input current: i in(avg) = i pk ? i ripple 2 amps step 4: calculate the nominal output current: i out(nom) = i in(avg) ?v in ? 0.8 v out amps step 5: derate output current: i out = i out(nom) ? 0.8 amps for low output voltages the output current capability will be increased. when using output disconnect (load cur- rent taken from v out ), these higher currents will cause the drop in the pmos switch to be higher resulting in reduced output current capability than those predicted by the preceding equations. inrush current when v cc is stepped from ground to the operating voltage while the output capacitor is discharged, a higher level of inrush current may ? ow through the inductor and schottky diode into the output capacitor. conditions that increase inrush current include a larger more abrupt voltage step at v in , a larger output capacitor tied to the cap pin and an inductor with a low saturation current. while the chip is designed to handle such events, the inrush current should not be allowed to exceed 1.5a. for circuits that use output capacitor values within the recommended range and have input voltages of less than 5v, inrush current remains low, posing no hazard to the device. in cases where there are large steps at v cc (more than 5v) and/or a large capacitor is used at the cap pin, inrush current should be measured to ensure safe operation. soft-start by connecting the shdn and ctrl pins as shown in figure 4, using an rc ? lter at the ctrl pin to limit the start-up current, the lt3495 is able to achieve soft-start. the small bias current of the ctrl pin allows using a small capacitor for a large rc time constant. the soft- start waveform is shown in figure 5. the soft-start time figure 5. soft-start waveform figure 4. soft-start circuitry sw cap v cc shdn ctrl v out fb gnd 3495 f04 lt3495 c ctrl r ctrl chip enable 500s/div 3495 f05 shdn voltage 5v/div inductor current 500ma/div v out voltage 5v/div ctrl voltage 2v/div v cc = 3.6v v out = 16v
lt3495/lt3495b/ lt3495-1/lt3495b-1 12 3495b1b1fa applications information figure 6. recommended board layout can be set by the value of r ctrl and c ctrl . the following expression can be used to design the soft-start time: t start up = r ctrl ?c ctrl ?in v shd n v shd n C 1.235 where v shdn is the voltage at shdn pin when the part is enabled. to ensure soft-start will work, the initial voltage at ctrl pin when the part is enabled should be close to 0v. the soft-start may not work if this initial condition is not satis? ed. output disconnect the lt3495 series has an output disconnect pmos that blocks the load from the input during shutdown. during normal operation, the maximum current through the pmos is limited by circuitry inside the chip. when the cap and v out voltage difference is more than 8.7v (typ), the cur- rent through the pmos is no longer limited, and can be much higher. as a result, forcing 8.7v or higher voltage from the cap to the v out pins can damage the pmos. in cases when the cap voltage is high and/or a large ca- pacitor is used at the cap pin, shorting v out to gnd can cause large pmos currents to ? ow. under this condition, the pmos peak current should be kept at less than 1a. also be aware of the thermal dissipation in the pmos at all times. in addition, if the input voltage is more than 8v, the pmos will turn on during shutdown, resulting in the output voltage no longer being blocked from the input. under this condition, the output voltage will be about 8v lower than the input voltage. board layout considerations as with all switching regulators, careful attention must be paid to the pcb board layout and component placement. to maximize ef? ciency, switch rise and fall times are made as short as possible. to prevent electromagnetic interfer- ence (emi) problems, proper layout of the high frequency switching path is essential. the voltage signal of the sw pin has sharp rising and falling edges. minimize the length and area of all traces connected to the sw pin and always use a ground plane under the switching regulator to minimize interplane coupling. in addition, the fb pin feeds into the internal error ampli? er and is sensitive to noise. minimizing the length and area of all traces to this pin is recommended. connect the feedback resistor r1 directly from the v out pin to the fb pin and keep the trace as short as possible. recommended component placement is shown in figure 6. gnd gnd v cc ctrl shdn sw cap cap v out fb gnd ctrl vias to ground plane required to improve thermal performance vias for cap ground return through second metal layer, capacitor grounds must be returned directly to ic ground shdn 3495 f06 gnd
lt3495/lt3495b/ lt3495-1/lt3495b-1 13 3495b1b1fa typical applications figure 8. one li-ion cell input boost converter with the lt3495b ef? ciency vs load current lt3495/lt3495b maximum output current vs output voltage v out r1 value required (m) maximum output current at 3v input (ma) 40 2.37 26 35 2.05 31 30 1.78 37 25 1.47 43 20 1.15 57 15 0.845 74 10 0.536 120 5 0.232 250 sw cap v cc shdn ctrl v out fb gnd r1 909k 3495 f07a lt3495 c1 4.7f l1 10h c2 2.2f c3 1f one li-ion cell turn on/off v out dimming c1: 4.7f, 6.3v, x5r, 0603 c2: 2.2f, 25v, x5r, 0805 c3: 1f, 25v, x5r, 0603 d1: diodes inc. b0540ws-7 l1: coilcraft lps4018-103mlb output 16v 70ma d1 figure 7. one li-ion cell input boost converter with the lt3495 sw cap v cc shdn ctrl v out fb gnd r1 909k 3495 f08a lt3495b c1 4.7f l1 6.8h c2 2.2f c3 1f one li-ion cell turn on/off v out dimming c1: 4.7f, 6.3v, x5r, 0603 c2: 2.2f, 25v, x5r, 0805 c3: 1f, 25v, x5r, 0603 d1: diodes inc. b0540ws-7 l1: sumida cr32-6r8 output 16v 70ma d1 ef? ciency vs load current load current (ma) efficiency (%) power loss (mw) 3495 f07b 90 80 50 60 70 40 400 320 80 160 240 0 0.1 10 100 1 v in = 3.6v load from cap load from v out load current (ma) efficiency (%) power loss (mw) 3495 f08b 90 80 50 60 70 40 400 320 80 160 240 0 0.1 10 100 1 v in = 3.6v load from cap load from v out
lt3495/lt3495b/ lt3495-1/lt3495b-1 14 3495b1b1fa one li-ion cell input boost converter with the lt3495-1/lt3495b-1 ef? ciency vs load current typical applications lt3495-1/lt3495b-1 maximum output current vs output voltage v out r1 value required (m) maximum output current at 3v input (ma) 40 2.37 12 35 2.05 15 30 1.78 18 25 1.47 21 20 1.15 28 15 0.845 36 10 0.536 63 5 0.232 120 ef? ciency vs load current sw cap v cc shdn ctrl v out fb gnd 665k 3495 ta02a lt3495b c1 4.7f l1 10h c2 2.2f c3 10f v in = 5v turn on/off v out dimming c1: 4.7f, 6.3v, x5r, 0603 c2: 2.2f, 25v, x5r, 0805 c3: 10f, 25v, x5r, 1206 d1: diodes inc. b0540ws-7 l1: coilcraft lps4018-103mlb v out = 12v 130ma d1 5v to 12v, 130ma boost converter load current (ma) efficiency (%) power loss (mw) 3495 ta02b 100 90 80 50 60 70 40 900 750 600 150 300 450 0 0.1 10 100 1000 1 load from cap load from v out load current (ma) efficiency (%) power loss (mw) 3495 f09b 90 80 50 60 70 40 250 200 50 100 150 0 0.1 10 100 1 v in = 3.6v load from cap load from v out sw cap v cc shdn ctrl v out fb gnd 909k 3495 f09a lt3495b-1/ lt3495-1 c1 2.2f l1 10h c2 1f c3 1f one li-ion cell turn on/off v out dimming c1: 2.2f, 6.3v, x5r, 0603 c2: 1f, 25v, x5r, 0603 c3: 1f, 25v, x5r, 0603 d1: diodes inc. b0540ws-7 l1: murata lqh32cn100k33 output 16v 30ma d1
lt3495/lt3495b/ lt3495-1/lt3495b-1 15 3495b1b1fa information furnished by linear technology corporation is believed to be accurate and reliable. however, no responsibility is assumed for its use. linear technology corporation makes no representa- tion that the interconnection of its circuits as described herein will not infringe on existing patent rights. ddb package 10-lead plastic dfn (3mm 2mm) (reference ltc dwg # 05-08-1722 rev ?) 2.00 0.10 (2 sides) note: 1. drawing conforms to version (wecd-1) in jedec package outline m0-229 2. drawing not to scale 3. all dimensions are in millimeters 4. dimensions of exposed pad on bottom of package do not include mold flash. mold flash, if present, shall not exceed 0.15mm on any side 5. exposed pad shall be solder plated 6. shaded area is only a reference for pin 1 location on the top and bottom of package 0.40 0.10 bottom view?xposed pad 0.64 0.05 (2 sides) 0.75 0.05 r = 0.115 typ r = 0.05 typ 2.39 0.05 (2 sides) 3.00 0.10 (2 sides) 1 5 10 6 pin 1 bar top mark (see note 6) 0.200 ref 0 ?0.05 (ddb10) dfn 0905 rev 0.25 0.05 2.39 0.05 (2 sides) recommended solder pad pitch and dimensions 0.64 0.05 (2 sides) 1.15 0.05 0.70 0.05 2.55 0.05 package outline 0.25 0.05 0.50 bsc pin 1 r = 0.20 or 0.25 45 chamfer 0.50 bsc ef? ciency vs load current typical applications wide input range sepic converter with 5v output sw cap v cc shdn ctrl v out fb gnd 232k 3495 ta03a lt3495b c1 2.2f l1 10h l2 10h c3 10f c2 1f input 2.6v to 12v turn on/off v out dimming c1: 2.2f, 16v, x5r, 0805 c2: 1f, 16v, x5r, 0805 c3: 10f, 16v, x5r, 1206 d1: fairchild semi mbr0540 l1, l2: coilcraft lps4018-103mlb v out = 5v 200ma, v in = 3.3v, 300ma, v in = 5v, 500ma, v in = 8v d1 load current (ma) efficiency (%) power loss (mw) 3495 ta03b 90 80 50 60 70 40 1200 1000 400 200 600 800 0 0.1 10 100 1000 1 v cc = 3.3v package description
lt3495/lt3495b/ lt3495-1/lt3495b-1 16 3495b1b1fa linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 fax: (408) 434-0507 www.linear.com ? linear technology corporation 2008 lt 0209 rev a ? printed in usa related parts typical application part number description comments lt1930/lt1930a 1a (i sw ), 1.2mhz/2.2mhz, high ef? ciency step-up dc/dc converters v in : 2.6v to 16v, v out(max) = 34v, i q = 4.2ma/5.5ma, i sd < 1a, thinsot package lt1945 (dual) dual output, boost/inverter, 350ma (i sw ), constant off- time, high ef? ciency step-up dc/dc converter v in : 1.2v to 15v, v out(max) = 34v, i q = 40a, i sd < 1a, 10-lead ms package lt1946/lt1946a 1.5a (i sw ), 1.2mhz/2.7mhz, high ef? ciency step-up dc/dc converters v in : 2.45v to 16v, v out(max) = 34v, i q = 3.2ma, i sd < 1a, 8-lead ms package lt3463/lt3463a dual output, boost/inverter, 250ma (i sw ), constant off-time, high ef? ciency step-up dc/dc converters with integrated schottkys v in : 2.3v to 15v, v out(max) = 40v, i q = 40a, i sd < 1a, dfn package lt3467/lt3467a 1.1a (i sw ), 1.3mhz/2.1mhz, high ef? ciency step-up dc/dc converters with soft-start v in : 2.4v to 16v, v out(max) = 40v, i q = 1.2ma, i sd < 1a, thinsot package lt3471 dual output, boost/inverter, 1.3a (i sw ), high ef? ciency boost-inverting dc/dc converter v in : 2.4v to 16v, v out(max) = 40v, i q = 2.5ma, i sd < 1a, dfn package lt3473/lt3473a 1a (i sw ), 1.2mhz, high ef? ciency step-up dc/dc converters with integrated schottky diode and output disconnect v in : 2.2v to 16v, v out(max) = 36v, i q = 100a, i sd < 1a, dfn package lt3494/lt3494a 180ma/350ma (i sw ), high ef? ciency step-up dc/dc converters with output disconnect v in : 2.1v to 16v, v out(max) = 40v, i q = 65a, i sd < 1a, dfn package lt3580 2a, 40v, 2.5mhz boost dc/dc converter v in : 2.5v to 32v, v out(max) = 40v, i q = 1ma, i sd < 1a, ms8e 3mm 3mm dfn-8 package adjustable high voltage power supply doesnt need a transformer output vs ctrl load current (ma) efficiency (%) power loss (mw) 3495 ta04c 90 80 50 40 60 70 30 600 500 200 100 300 400 0 0.1 10 100 1 v in = 5v v out = 120v load current (ma) 0 v out peak-to-peak ripple (mv) 700 600 400 500 300 200 100 0 16 8 3495 ta04d 20 12 4 v in = 5v v out = 120v sw cap v cc shdn ctrl v out fb gnd 10.7k v out 15v to 120v 10ma (v in = 3.3v) 18ma (v in = 5v) 35ma (v in = 8v) 3495 ta04a lt3495b c1 4.7f l1 22h c2 1f d1 d2 d3 d4 c4 1f c6 1f 909k c5 1f c7 1f c3 1f 3.3v to 8v input turn on/off v out dimming c1: 4.7f, 16v, x5r, 0805 c2-c7: 1f, 50v, x5r, 0805 d1-d5: diode inc. b0540ws-7 l1: coilcraft lps4018-223mlb d5 danger high voltage! operation by high voltage trained personnel only ctrl voltage (v) 0 v out voltage (v) 150 120 60 90 30 0 1.2 0.6 1.8 3495 ta04b 2.1 0.9 0.3 1.5 output voltage ripple vs load current ef? ciency vs load current

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