View MAX5025EUT-T_9051441.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

general description the max5025?ax5028 constant-frequency, pulse- width modulating (pwm), low-noise boost converters are intended for low-voltage systems that often need a locally generated high voltage. these devices are capable of generating low-noise, high output voltages required for varactor diode biasing in tv tuners, set-top boxes, and pci cable modems. the max5025 max5028 operate from as low as 3v and switch at 500khz. the constant-frequency, current-mode pwm architec- ture provides for low output noise that is easy to filter. a 40v lateral dmos device is used as the internal power switch, making the devices ideal for boost converters up to 36v. the max5025/max5026 adjustable versions require the use of external feedback resistors to set the output voltage. the max5027/max5028 offer a fixed 30v output. these devices are available in a small, 6- pin sot23 package. applications tv tuner power supply low-noise varactor diode biasing set-top box tuner power supply pci cable modem voice-over-cable lcd power supply avalanche photodiode biasing features ? input voltage range: 3v to 11v (max5026/max5028) 4.5v to 11v (max5025/max5027) ? wide output voltage range: v cc to 36v ? output power: 120mw (max) ? user-adjustable output voltage with max5025/max5026 using external feedback resistors ? fixed 30v output voltage: max5027/max5028 ? internal 1.3 (typ), 40v switch ? constant pwm frequency provides easy filtering in low-noise applications ? 500khz (typ) switching frequency ? 1a (max) shutdown current ? small, 6-pin sot23 package max5025?ax5028 500khz, 36v output, sot23, pwm step-up dc-dc converters ________________________________________________________________ maxim integrated products 1 gnd fb 16lx 5v cc pgnd max5025 max5028 sot23-6 top view 2 34 shdn pin configuration v out 30v c1 c2 l1 v cc = 4.5v to 11v (max5027) v cc = 3v to 11v (max5028) d1 v cc gnd fb pgnd lx max5027 max5028 shdn typical operating circuit 19-2239; rev 2; 3/09 evaluation kit available ordering information pa rt temp range pin- pack age max5025 eut-t -40c to +85c 6 sot23-6 max5026 eut-t -40c to +85c 6 sot23-6 max5027 eut-t -40c to +85c 6 sot23-6 max5028 eut-t -40c to +85c 6 sot23-6 for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. selector guide appears at end of data sheet.
max5025?ax5028 500khz, 36v output, sot23, step-up dc-dc converters 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v cc = 5v, shdn = v cc , t a = -40? to +85?, unless otherwise noted. typical values are at t a = +25?.) (note 1) stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress rating s only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. v cc to gnd ............................................................-0.3v to +12v pgnd to gnd .......................................................-0.1v to +0.1v fb to gnd (max5025/max5026)...............-0.3v to (v cc + 0.3v) fb to gnd (max5027/max5028)...........................-0.3v to +40v shdn to gnd.............................................-0.3v to (v cc + 0.3v) lx to gnd ..............................................................-0.3v to +45v peak lx current ................................................................600ma operating temperature range ...........................-40? to +85? continuous power dissipation (t a = +70 c) 6-pin sot23 (derate 8.7mw/? above +70?)..........695.7mw junction temperature ......................................................+150? storage temperature range .............................-65? to +165? lead temperature (soldering 10s) ..................................+300? parameter symbol conditions min typ max units supply voltage max5026/max5028 3.0 11 input voltage range v cc max5025/max5027 4.5 11 v undervoltage lockout v uvlo rise/fall, hysteresis = 3mv 2.25 2.65 2.95 v supply current i cc max5025/max5026, fb = 1.4v max5027/max5028, fb = 35v 350 1000 ? shutdown current i shdn shdn = gnd 0.01 1a boost converter max5025/max5027 345 500 1000 switching frequency f sw max5026/max5028, v cc = 3.3v 410 500 670 khz max5025/max5027, i load = 2ma, v cc = 4.5v to 11v, v out = 30v 0.25 line regulation max5026/max5028, i load = 0.5ma, v cc = 3v to 11v, v out = 30v 0.25 %/v max5025/max5027, v cc = 5v, i load = 0 to 4ma, v out = 30v 2.0 load regulation max5026/max5028, v cc = 3.3v, i load = 0 to 1ma, v out = 30v 1.0 % thermal shutdown 140 ? thermal shutdown hysteresis 2c
max5025?ax5028 electrical characteristics (continued) (v cc = 5v, shdn = v cc , t a = -40? to +85?, unless otherwise noted. typical values are at t a = +25?.) (note 1) parameter symbol conditions min typ max units max5025, v cc = 4.5v to 11v 1.19 1.25 1.31 max5027, v cc = 4.5v to 11v 28.5 30.0 31.5 max5026, v cc = 3.3v to 11v 1.212 1.25 1.288 fb set point v fb max5028, v cc = 3.3v to 11v 29.0 30 31 v max5025/max5026, fb = 1v 110 310 na fb input bias current i fb max5027/max5028, fb = 30v 100 170 ? output voltage adjustment range max5025/max5026 v cc + 1 36 v lx output max5026/max5028, v cc = 3v 2.0 4.0 v cc = 5v 1.3 3.0 lx on-resistance r on i lx = 40ma v cc = 11v 1.0 2.5 switch current limit i lim note 2 260 ma max5025/max5026, v fb = 1.4v lx leakage current v lx = 40v max5027/max5028, v fb = 35v 0.01 10 ? logic input: shdn input low level v il 0.8 v input high level v ih 2.4 v input bias current -1 1 a note 1: all devices are 100% production tested at t a = +25?. all temperature limits are guaranteed by design. note 2: switch current-limit accuracy is typically ?0% and is a function of the input voltage. i lim = (v in /5) (260ma). 500khz, 36v output, sot23, step-up dc-dc converters _______________________________________________________________________________________ 3
max5025?ax5028 500khz, 36v output, sot23, step-up dc-dc converters 4 _______________________________________________________________________________________ 0 20 10 40 30 50 60 80 70 90 0246810 max5025-28 toc01 load current (ma) efficiency (%) efficiency vs. load current (v out = 12v) max5026 v cc = 5v, v out = 12v circuit of figure 2. r1 = 147k , r2 = 16.2k 0 20 10 50 40 30 80 70 60 90 04 268 max5025-28 toc02 load current (ma) efficiency (%) efficiency vs. load current (v out = 15v) max5026 v cc = 5v, v out = 12v circuit of figure 2. r1 = 147k , r2 = 13k 0 20 10 30 60 70 50 40 80 012345 max5025-28 toc03 load current (ma) efficiency (%) efficiency vs. load current (v out = 24v) max5026 v cc = 5v, v out = 24v circuit of figure 2. r1 = 147k , r2 = 8.07k 0 10 30 20 50 60 40 70 01234 max5025-28 toc04 load current (ma) efficiency (%) efficiency vs. load current (v out = 30v) max5026 v cc = 5v, v out = 30v circuit of figure 2. r1 = 147k , r2 = 6.34k 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 01234 max5025-28 toc05 load current (ma) startup voltage (v) max5026 minimum startup voltage vs. load current 0 150 100 50 200 250 300 350 400 450 500 036912 max5025-28 toc06 supply voltage (v) supply current ( a) max5026/max5028 supply current vs. supply voltage current into v cc pin device not switching 0 2 4 6 8 10 12 14 16 357911 max5025-28 toc07 supply voltage (v) no load supply current (ma) max5026 no load supply current vs. supply voltage circuit of figure 2 v out = 30v 150 350 250 550 450 750 650 850 -40 0 20 -20 40 60 80 supply current vs. temperature max5025-28 toc08 temperature ( c) supply current ( a) current into v cc pin v cc = 11v v cc = 9v v cc = 7v v cc = 5v v cc = 3v 200 300 250 450 400 350 600 550 500 650 -40 0 20 -20 40 60 80 max5025-28 toc09 temperature ( c) switching frequency (khz) max5026 switching frequency vs. temperature v cc = 5v v out = 30v circuit of figure 2. typical operating characteristics (v cc = 5v, v out = 30v, t a = +25?, unless otherwise noted.)
max5025?ax5028 typical operating characteristics (continued) (v cc = 5v, v out = 30v, t a = +25?, unless otherwise noted.) 500khz, 36v output, sot23, step-up dc-dc converters _______________________________________________________________________________________ 5 exiting shutdown max5025-28 toc10 5v output voltage 20v/div inductor current 50ma/div shutdown voltage 5v/div 30v 5v 2ms/div max5026, v cc = 5v, v out = 30v, i load = 1ma. circuit of figure 3 entering shutdown max5025-28 toc11 30v output voltage 20v/div shutdown voltage 5v/div 5v 5v 0v 100ms/div max5026, v cc = 5v, v out = 30v, i load = 1ma. circuit of figure 3 max5025-28 toc12 lx pin 20v/div v out 2mv/div ac-coupled i l 100ma/div 0v 0ma 1 s/div max5026, v cc = 5v, v out = 30v, i load = 0.1ma. circuit of figure 2 light-load switching waveform without rc filter max5025-28 toc13 lx pin 20v/div v out 1mv/div ac-coupled i l 100ma/div 0v 0ma 1 s/div max5026, v cc = 5v, v out = 30v, i load = 0.1ma. circuit of figure 3 light-load switching waveform with rc filter max5025-28 toc14 lx pin 20v/div v out 5mv/div ac-coupled i l 200ma/div 0v 0ma 1 s/div max5026, v cc = 5v, v out = 30v, i load = 2ma. circuit of figure 2 medium-load switching waveform without rc filter max5025-28 toc15 lx pin 20v/div v out 1mv/div ac-coupled i l 200ma/div 0v 0ma 1 s/div max5026, v cc = 5v, v out = 30v, i load = 2ma. circuit of figure 3 medium-load switching waveform with rc filter
max5025?ax5028 500khz, 36v output, sot23, step-up dc-dc converters 6 _______________________________________________________________________________________ typical operating characteristics (continued) (v cc = 5v, v out = 30v, t a = +25?, unless otherwise noted.) max5025-28 toc17 lx pin 20v/div v out 1mv/div ac-coupled i l 200ma/div 0v 0ma 1 s/div max5026, v cc = 5v, v out = 30v, i load = 4ma. circuit of figure 3 heavy-load switching waveform with rc filter load transient response max5025-28 toc18 output voltage 200mv/div ac-coupled load current 10ma/div 0mv 0ma 1ms/div max5026, v cc = 5v, v out = 30v, i load = 0 to 4ma. circuit of figure 2 line transient response max5025-28 toc19 output voltage 1mv/div ac-coupled input voltage 100mv/div ac-coupled 0mv 0mv 2ms/div max5026, v cc = 5v to 5.2v, v out = 30v, i load = 1ma. circuit of figure 2 max5025-28 toc20 1.230 1.235 1.245 1.240 1.260 1.265 1.255 1.250 1.270 fb pin voltage (v) -40 0 20 -20 40 60 80 temperature ( c) max5026 fb pin voltage vs. temperature v cc = 11v v cc = 5v v cc = 3v 29.0 29.4 29.2 29.8 29.6 30.2 30.0 30.4 -40 0 20 -20 40 60 80 max5025-28 toc21 temperature ( c) fb pin voltage (v) max5028 fb pin voltage vs. temperature v cc = 11v v cc = 5v v cc = 3v max5025-28 toc16 lx pin 20v/div v out 5mv/div ac-coupled i l 200ma/div 0v 0ma 1 s/div max5026, v cc = 5v, v out = 30v, i load = 4ma. circuit of figure 2 heavy-load switching waveform without rc filter
max5025?ax5028 500khz, 36v output, sot23, step-up dc-dc converters _______________________________________________________________________________________ 7 0 0.015 0.010 0.005 0.025 0.020 0.045 0.040 0.035 0.030 0.050 -40 -20 0 20 40 60 80 max5025-28 toc23 temperature ( c) lx leakage current ( a) lx leakage current vs. temperature current into lx pin v lx = 40v 32 31 30 29 28 02 1 345 load regulation max5025-28 toc24 load current (ma) output voltage (v) max5026 v cc = 5v with rc filter (circuit of figure 3) without rc filter (circuit of figure 2) max5025-28 toc25 input voltage (v) maximum load current (ma) max5026 maximum load current vs. input voltage 9 7 5 1 10 100 0.1 311 a: v out = 12v b: v out = 24v c: v out = 30v d: v out = 32v e: v out = 36v a b e c d typical operating characteristics (continued) (v cc = 5v, v out = 30v, t a = +25?, unless otherwise noted.) 0.5 1.0 2.0 1.5 2.5 3.0 -40 0 -20 20 40 60 80 max5025-28 toc22 temperature ( c) r on ( ) switch on-resistance vs. temperature v cc = 3v v cc = 5v v cc = 11v max5026
max5025?ax5028 500khz, 36v output, sot23, step-up dc-dc converters 8 _______________________________________________________________________________________ pin description pin max5025/ max5026 max5027/ max5028 name function 1 1 pgnd power ground. connect directly to local ground plane. use a star ground configuration for low noise. 2 2 gnd ground. connect directly to local ground plane. 3fb feedback pin. reference voltage is approximately 1.25v. connect resistive-divider tap here. minimize trace area at fb. see setting the output voltage section. ?fb feedback pin. connect v out to fb for +30v. internal resistors divide down the output voltage. 44 shdn shutdown pin. connect to v cc to enable device. connect to gnd to shut down. 55v cc input supply voltage. bypass with a 4.7? ceramic capacitor. 66lx drain of internal 40v n-channel dmos. connect inductor/diode to lx. minimize trace area at this pin to keep emi down. detailed description the max5025?ax5028 current-mode pwm con- trollers operate in a wide range of dc-dc conversion applications including boost, flyback, and isolated out- put configurations. these converters provide low- noise, high output voltages making them ideal for var- actor diode tuning applications as well as tft lcd bias. other features include shutdown, fixed 500khz pwm oscillator, and a wide input range: 3v to 11v for max5026/max5028 and 4.5v to 11v for max5025/ max5027. the max5025?ax5028 operate in discontinuous mode in order to reduce the switching noise at the out- put. other continuous mode boost converters generate a large voltage spike at the output when the lx switch turns on because there is a conduction path between the output, diode, and switch to ground during the time needed for the diode to turn off. to reduce the output noise even further, the lx switch turns off by taking 40ns typically to transition from ?n to ?ff.?as a consequence, the positive slew rate of the lx node is reduced and the current from the induc- tor does not ?orce?the output voltage as hard as would be the case if the lx switch were to turn off more quickly. pwm controller the heart of the max5025?ax5028 current-mode pwm controllers is a bicmos multi-input comparator that simultaneously processes the output-error signal and switch current signal. the main pwm comparator is direct summing, lacking a traditional error amplifier and its associated phase shift. the direct summing configuration approaches ideal cycle-by-cycle control over the output voltage since there is no conventional error amp in the feedback path. the device operates in pwm mode using a fixed-fre- quency, current-mode operation. the current-mode feedback loop regulates peak inductor current as a function of the output error signal. shdn input the shdn pin provides shutdown control. connect shdn to v cc for normal operation. to disable the device, connect shdn to gnd. design procedure the max5025?ax5028 can operate in a number of dc-dc converter configurations including step-up, sin- gle-ended primary inductance converter (sepic), and flyback. the following design discussions are limited to step-up, with a complete circuit shown in the application circuits section. setting the output voltage the output voltage of the max5027/max5028 is fixed at 30v. the output voltage of the max5025/max5026 is set by two external resistors (r1 and r2, figure 2 and figure 3). first select the value of r2 in the 5k to 50k range. r1 is then given by:
max5025?ax5028 500khz, 36v output, sot23, step-up dc-dc converters _______________________________________________________________________________________ 9 where v ref is 1.25v determining peak inductor current if the boost converter remains in the discontinuous mode of operation, then the approximate peak inductor current, i lpeak , is represented by the formula below: where t s is the period, v out is the output voltage, v in is the input voltage, i out is the output current, and is the efficiency of the boost converter. determining the inductor value 47? is the recommended inductor value when the out- put voltage is 30v and the input voltage is 5v. in gener- al, the inductor should have a current rating greater than the current-limit value. for example, the inductor? current rating should be greater than 150ma to support a 4ma output current. equivalent series resistance (esr) should be below 1 for reasonable efficiency. due to the max5025?ax5028? high switching fre- quency, inductors with a ferrite core or equivalent are recommended. powdered iron cores are not recom- mended due to their high losses at frequencies over 500khz. table 1 shows a list of vendors and 47? inductor parts. for 4ma output current and output voltages other than 30v, the inductor can be simply scaled in value according to the following formula: use the following formula to calculate the upper bound of the inductor value at different output voltages and output currents. this is the maximum inductance value for discontinuous mode operation. calculate the lower bound, l lower , for the acceptable inductance value using the following formula, which will allow the maximum output current to be delivered with- out reaching the peak current limit: notice that the switch current limit, (v in /5)(260ma), is a function of the input voltage, v in . the current rating of the inductor should be greater than the switch current limit. l tv vi v ma lower s out in out in = ? () () ? ? ? ? ? ? 2 5 260 2 l vv vt iv upper out in s out out in = ? () 2 2 2 l hv v v out in = () ? () () 47 25 i tv vi l lpeak s out in out = ? () 2 rr v v out ref 12 1 = ? ? ? ? ? ? - control logic main pwm comparator current- limit comparator fb ref -a +a +c -c max5025 max5026 thermal shutdown oscillator ulvo pgnd 3 gnd 2 v cc 5 shdn 4 1 6 lx n table 1. inductor vendors vendor phone fax part number of 47? inductor coilcraft 847-639-6400 847-639-1469 dt1608c-473 sumida 847-545-6700 847-545-6720 cdrh4d28-470 toko 847-297-0070 847-699-7864 a915by-470m figure 1. functional diagram
max5025?ax5028 500khz, 36v output, sot23, step-up dc-dc converters 10 ______________________________________________________________________________________ for a design in which v in = 5v, v out = 30v, i out = 4ma, = 0.5, and t s = 2?, l upper = 87? and l lower = 12?. for a worst-case scenario in which v in = 4.75v, v out = 29v, i out = 4.4ma, = 0.5, and t s = 1.25?, l upper = 46? and l lower = 9?. the choice of 47? as the recommended inductance value is reasonable given the worst-case scenario above. in general, the higher the inductance, the lower the switching noise. load regulation is also better with higher inductance. diode selection the max5025?ax5028? high switching frequency demands a high-speed rectifier. schottky diodes are recommended for most applications because of their fast recovery time and low forward-voltage drop. ensure that the diode? peak current rating is greater than or equal to the peak inductor current. also, the diode reverse breakdown voltage must be greater than v out . table 2 lists diode vendors. capacitor selection output filter capacitor the output filter capacitor should be 1? or greater. to achieve low output ripple, a capacitor with low esr, low esl, and high capacitance value should be selected. for very low output ripple applications, the output of the boost converter can be followed by an rc filter to fur- ther reduce the ripple. figure 3 shows a 100 , 1? fil- ter used to reduce the switching output ripple to 1mvp-p. x7r ceramic capacitors are better for this boost appli- cation because of their low esr and tighter tolerance over temperature than the y5v ceramic capacitors. table 3 below lists manufacturers of recommended capacitors. input capacitor bypass v cc with a 4.7? ceramic capacitor as close to the ic as is practical. applications information layout considerations the max5025?ax5028 switch at high speed, man- dating careful attention to layout for optimum perfor- mance. protect sensitive analog grounds by using a star ground configuration. minimize ground noise by connecting gnd, pgnd, the input bypass-capacitor ground lead, and the output-filter ground lead to a sin- gle point (star ground configuration). also, minimize table 2. schottky diode vendors vendor phone fax part numbers comchip 510-657-8671 510-657-8921 cdbs1045 panasonic 408-942-2912 408-946-9063 ma2z785 st-microelectronics 602-485-6100 602-486-6102 tmmbat48 vishay-telefunken 402-563-6866 402-563-6296 bas382 zetex 631-360-2222 631-360-8222 zhcs500 table 3. capacitor table company phone fax part numbers grm42-2x7r105k050ad (1? capacitor) murata 814-237-1431 814-238-0490 grm32-1210r71c475r (4.7? capacitor) umk325bj105kh (1? capacitor) taiyo yuden 408-573-4150 408-573-4159 emk316bj475ml (4.7? capacitor) c3225x7r1h155k (1.5? capacitor) tdk 847-803-6100 847-803-6296 c3225x7r1h105k (1? capacitor)
max5025?ax5028 500khz, 36v output, sot23, step-up dc-dc converters ______________________________________________________________________________________ 11 trace lengths to reduce stray capacitance, trace resis- tance, and radiated noise. the trace between the out- put voltage-divider (max5025/max5026) and the fb pin must be kept short, as well as the trace between gnd and pgnd. inductor layout the shielded drum type inductors have a small air gap around the top and bottom periphery. the incident fring- ing magnetic field from this air gap to the copper plane on the pc board tends to reduce efficiency. this is a result of the induced eddy currents on the copper plane. to minimize this effect, avoid laying out any copper planes under the mounting area of these inductors. 30v boost application circuit figures 2 and 3 show the max5025/max5026 operat- ing in a 30v boost application. figure 3 has an rc filter to reduce noise at the output. these circuits provide output currents greater than 4ma with an input voltage of 5v or greater. they are designed by following the design procedure section. operating characteristics of these circuits are shown in the typical operating characteristics section. v cc v out +30v gnd fb pgnd c1 4.7 f c2 1 f lx l1 47 h max5025 max5026 c2 1 f v cc = 4.5v to 11v (max5025) v cc = 3v to 11v (max5026) d1 r1 147k r2 6.34k toko 47 h inductor a915by-470m zetex schottky diode zhcs500 shdn figure 2. adjustable 30v output circuit v cc v out +30v gnd fb pgnd c1 4.7 f c2 1 f lx l1 47 h max5025 max5026 c3 1 f v cc = 4.5v to 11v (max5025) v cc = 3v to 11v (max5026) d1 r1 147k r3 100 r2 6.34k toko 47 h inductor a915by-470m zetex schottky diode zhcs500 shdn figure 3. adjustable 30v output circuit with rc filter
max5025?ax5028 500khz, 36v output, sot23, step-up dc-dc converters 12 ______________________________________________________________________________________ selector guide part output frequency tolerance fb set point tolerance input voltage max5025 adjustable -31% to +100% 5% 4.5v to 11v max5026 adjustable -18% to +34% 3% 3v to 11v max5027 fixed 30v -31% to +100% 5% 4.5v to 11v max5028 fixed 30v -18% to +34% 3% 3v to 11v package information for the latest package outline information and land patterns, go to www.maxim-ic.com/packages . package type package code document no. 6 sot23 s8-2 21-0058 ____________________chip information transistor count: 365 process: bicmos
maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ____________________ 13 2009 maxim integrated products maxim is a registered trademark of maxim integrated products, inc. max5025?ax5028 500khz, 36v output, sot23, step-up dc-dc converters revision history revision number revision date description pages changed 0 10/01 initial release 1 12/01 released the max5027 1 2 3/09 revised the absolute maximum ratings section. 2

▲Up To Search▲

Price & Availability of MAX5025EUT-T

	To Download MAX5025EUT-T Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .