View AX3842S_1571267.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

page no. : 1/12 avantics - ax3842 series specification no.: 050308-fe0008 ax3842p / AX3842S high performance current mode pwm controlers description the ax3842 series is high performance fixed frequency current mode controllers. that is specifically designed for off-line and dc to dc converter applications offering the designer a costeffective solution with minimal external components. these integrated circuits feature a trimmed oscillator for precise duty cycle control. a temperature compensated reference, high gain error amplifier, current sensing compara-tor, and a high current totem pole output ideally suited for driving a power mosfet. also included are protective features consisting of input and reference undervoltage lockouts each with hysteresis, cycle-by-cycle current limiting, programmable output deadtime, and a latch for single pulse metering. features ? trimmed oscillator for precise frequency control ? oscillator frequency guaranteed at 250 khz ? current mode operation to 500 khz ? automatic feed forward compensation ? latching pwm for cycle-by-cycle current limiting ? internally trimmed reference with undervoltage lockout ? high current totem pole output ? undervoltage lockout with hysteresis ? low startup and operating current absolute maximum ratings symbol parameter value unit v i supply voltage (low impedance source) 30 v v i supply voltage (i i <30ma) self limiting i o output current 1 a e o output energy (capacitive load) 5 uj analog inputs (pin 2, 3) -0.3 to 5.5 v error amplifier output sink current 10 ma p tot power dissipation at t amb 25 o c 800 mw t stg storage temperature range -65 to 150 o c t j junction operating temperature -40 to 150 o c t l lead temperature (soldering 10s) 300 o c thermal data symbol description dip-8 so-8 units rth j-amb thermal resistance junction-ambient 100 150 o c/w 8-lead plastic so-8 package code: s ? 8-lead plastic dip-8 package code: p
page no. : 2/12 avantics - ax3842 series specification no.: 050308-fe0008 block diagram pin connection (top view) package function description pin1: compensation this pin is the error amplifier output and is made available for loop compensation. pin2: voltage feedback this is the inverting input of the error amplifier. it?s normally connected to the switching power supply output through a resistor divider. pin3: current sense a voltage proportional to inductor current is connected to this input. the pwm uses this information to terminate the output switch conduction. pin4: rt/ct the oscillator frequency and maximum output duty cycle are programmed by connecting resistor rt to vref and cpacitor ct to ground. operation to 500khz is possible. pin5: ground this pin is the combined control circuitry and power ground. pin6: output this output directly drives the gate of a power mosfet. peak currents up to 1a are sourced and sunk by this pin. pin7: vcc this pin is the positive supply of the control ic. 1234 5 6 7 8 dip-8 1234 5 6 7 8 so-8 pin8: vref this is the reference output. it provides charging current for capacitor ct through resistor rt. 1v 34v 2r r 1 2 3 4 5 6 7 8 vcc ground vfb comp current sense + - error amp. vref good logic 2.50v current sense comparator t uvlo 5v ref internal bias pwm latch output vref 5v 50ma s/r rt/ct s r osc
page no. : 3/12 avantics - ax3842 series specification no.: 050308-fe0008 electrical characteristics unless otherwise stated, specifications apply for 0 t amb 70 c v cc =15v (note 1) ; r t =680 ? , c t =0.022uf for triangular mode, r t =10k, c t =3.3nf for sawtooth mode symbol parameter test conditions min. typ. max. units reference section v ref reference output voltage tj=25 c,io=1ma 4.90 5 5.1 v ? v ref line regulation 12v v in 25v -2.020mv ? v ref load regulation 1ma io 20ma -3.025mv ? v ref / ? t temperature stability (note 2) -0.2- mv/ c total output variation line, load, temp (note 2) 4.82 - 5.18 v e n output noise voltage 10hz f 10khz,tj=25 c (note 2) -50- uv long term stability ta=125 c,1000hrs (note 2) -5-mv i sc output short current ta=25 c -30 -100 -180 ma oscillator section t j =25 c 47 52 57 khz f osc frequency t low t a t high 46 52 60 khz ? f osc / ? v frequency change with volt. 12v v cc 25v -0.21 % t low t a t high (note 2) -5-% ? f osc / ? t frequency change with temp. t j =25 c -0.5- % v osc oscillator voltage swing peak to peak - 1.7 - v t j =25 c 7.8 8.3 9.3 ma i dischg discharge current (v osc =2v) t low t a t high 7.2 - 9.5 ma error amplifier section v 2 voltage feedback input v o =2.5v 2.42 2.50 2.58 v i b input bias current v fb =5.0v - -0.1 -2.0 ua a vol open loop voltage gain 2 v o 4 v 65 90 - db bw unity gain bandwidth t j =25 c (note 2) 0.7 1.0 - mhz psrr power supply rejection ratio 12v v cc 25v 60 70 - db sink (v o =1.1v, v fb =2.7v) 2.0 12 - ma i o output current source (v o =5.0v, v fb =2.3v) -0.5 -1.0 - ma v out-high output voltage swing high state v fb =2.3v, r l =15k to ground 5 6 - v v out-low output voltage swing low state v fb =2.7v, r l =15k to v ref -0.71.1v current sense section g v current sense input voltage gain (notes 3 & 4) 2.85 3.0 3.15 v/v v 3 maximum input signal v pin1 =5v (note 3) 0.9 1.0 1.1 v svr supply voltage rejection ratio 12v v cc 25v (note 3) -70- db i b input bias current - -2.0 -10 ua propagation delay tj=25 c (note 2) - 150 300 ns
page no. : 4/12 avantics - ax3842 series specification no.: 050308-fe0008 electrical characteristics (continued) symbol parameter test conditions min. typ. max. units output section i sink =20ma - 0.1 0.4 v v ol output voltage (low state) i sink =200ma - 1.5 2.2 v i source =20ma 13 13.5 - v v oh output voltage (high state) i source =200ma 12 13.4 - v v ols output voltage with uvlo activated v cc =6v, i sink =1ma - -0.1 -1.1 v t r output voltage rise time t j =25 c, c l =1.0nf (note 2) - 50 150 ns t f output voltage fall time t j =25 c, c l =1.0nf (note 2) - 50 150 ns under-voltage lockout section start threshold 14.5 16 17.5 v min. operating voltage after turn on 8.5 10 11.5 v pwm section dc max maximum duty cycle 94 96 - % dc min minimum duty cycle - - 0 % total device i st start-up current - 0.1 0.5 ma i i operating supply current v pin2 =v pin3 =0, r t =10k, c t =3.3nf -1117ma v iz vcc zener voltage i cc =25 ma - 34 - v note 1: adjust v cc above the start threshold before setting at 15v. note 2: these parameters, although guaranteed are not 100% tested in production. note 3: parameter measured at trip point of latch with v pin2 =0. note 4: gain defined as: a=v pin1 /v pin3 , 0 v pin3 0.8v
page no. : 5/12 avantics - ax3842 series specification no.: 050308-fe0008 characteristics curve oscillator frequency & timing resistance 1k 10k 100k 1000k 10000k 100 1000 10000 100000 rt( ? ) fo(hz) ct=1.0nf ct=2.2nf ct=4.7nf current sense input threshold & error amp output voltage 0 0.2 0.4 0.6 0.8 1 1.2 02468 vo (v) vth (v) ta=125 o c ta=-40 o c ta=25 o c vcc=15v reference voltage change & source current 0 10 20 30 40 50 60 0 20 40 60 80 100 120 ire f (ma ) ta=125 o c ta=25 o c ta=-40 o c vcc=15v oscillator discharge current & temperate 7 7.5 8 8.5 9 -50 -25 0 25 50 75 100 125 ta ( o c) idischg (ma) vi=15v vosc=2v error amp open-loop gain and phase & frequency -20 0 20 40 60 80 100 10 100 1000 10000 100000 1000000 10000000 f (hz) (db) gain phase vcc=15v vo=2v to 4v r l =100k ta=25 o c 30 60 90 120 150 180 maximum duty cycle & timing resistance 0 20 40 60 80 100 100 1000 10000 100000 rt( ? ) dcmax (%)
page no. : 6/12 avantics - ax3842 series specification no.: 050308-fe0008 reference short circuit current &temperature 50 60 70 80 90 100 110 -50 -25 0 25 50 75 100 125 ta ( o c) isc (ma) vcc=15v rl 0.1 ? supply current & supply voltage 0 5 10 15 20 25 0 10203040 vi (v) ii (ma) r t =10k c t =3.3nf output saturation voltage & load current 0 1 2 3 4 0 200 400 600 800 io (ma ) vsat (v) sink saturation (load to vcc) ta=-40 o c ta=25 o c vcc=15v 80us pulsed load 120hz rate output saturation voltage & load current -4 -3 -2 -1 0 0 200 400 600 800 io (ma ) vsat (v) source saturation (load to ground) ta=25 o c ta=-40 o c vcc=15v 80us pulsed load 120hz rate
page no. : 7/12 avantics - ax3842 series specification no.: 050308-fe0008 application information open loop test circuit oscillator and output waveforms error amp configuration under voltage lockout 4.7k 1k 4.7k 5k 100k rt 0.1uf 0.1uf ct 1w 1k error amp. adjust i adjust hpn2222a comp rt/ct v vcc output ground ground output vcc vref 1 2 3 4 5 6 7 8 ref sense i sense v fb a ax3842 rt ct 4 5 6 7 8 5v reg pwm clock oscillator id output gnd ct output large rt / small ct ct output small rt / lar g e ct vcc 1 2 3 high peak currents associated with capacitive loads necessitate careful grounding techniques. timing and bypass capacitors should be connected close to pin5 in a single point ground. the transistor and 5k ? p otentiometerare used to sam p lethe oscillator waveform and a pp l y an ad j ustable ram p to p in3. zi zf v comp 2.5v 1ma 1 2 fb + - on/off command von voff ax3842 to rest of ic 16v 10v icc <17ma <0.5ma vcc voff von vi 7
page no. : 8/12 avantics - ax3842 series specification no.: 050308-fe0008 current sense circuit slope compensation techniques isolated mosfet drive and current transformer sensing peak current (is) is determined by the formula is(max.) 1v/rs a small rc filter may be required to suppress switch transients. r rs c 2r comp is current sense gnd 1 3 5 error ampl. r1v current sense comparator 5.0vref + + + - - vcc s r q comp/latch c r rs ns np q1 vin isolation boundary 3 6 7 vgs waveforms 50%dc 25%dc ipk=((vpin1-1.4)/3rs)(ns/np) + 0 - + 0 - r1 8 rs 5 r 4 rt 3 ct slope ax3842 is v reg rt/ct i sense gnd r1 8 rs 5 r 4 rt 3 ct slope ax3842 is v reg rt/ct i sense gnd
page no. : 9/12 avantics - ax3842 series specification no.: 050308-fe0008 2n3903 2n3905 r + - osc bias 1ma + ea 1 2 4 5 8 r 2r r latched shutdown error amplifier compensation external clock synchronization ri rd rf cf 2r r + + - 1 2 2.5v ea 1ma 5 from vo rp rf cf 2r r + + - 1 2 2.5v ea 1ma 5 from vo rd ri cp scr must be selected for a holding current of less than 0.5ma at ta(min). the simple two transistor circuit can be used in p lace of the scr as shown. all resistors are 10k. error amp compensation circuit for stabilizing any current-mode topology except for boost and flyback converters operating with continuous inductor current error amp compensation circuit for stabilizing current-mode boost and flyback topologies operating with continuous inductor current. the diode clamp is required if the sync amplitude is large enough to cause the bottom side of ct to go more than 300mv below ground 0.01uf ct rt 47 r r r 2r 1 2 4 5 8 + - + ea osc bias vref external sync input
page no. : 10/12 avantics - ax3842 series specification no.: 050308-fe0008 rs vclamp comp/latch q1 bc109 vcc vin 7 6 5 1 2 r2 5vref c r 2r 5 ea + - 1ma + r r 4 8 osc bias s r q + 1v + - r1 + 7 external duty cycle clamp and multi unit synchronization soft-start circuit soft-start and error amplifier output duty cycle clamp r r r 2r 1 2 4 5 8 + ea osc bias ra rb 5k 5k 5k c 2 3 4 5 6 7 8 1 + - r s q vref ne555 to additional ax3842 + - + - f=1.44/((ra+2rb)c), dmax=rb/(ra+2rb) vclamp=r1/(r1+r2) where 0 page no. : 11/12 avantics - ax3842 series specification no.: 050308-fe0008 dip-8 dimension so-8 dimension important notice: ? all rights are reserved. reproduction in whole or in part is prohibited without the prior written approval of avantic. ? avantics reserves the right to make changes to its products without notice. ? avantics semiconductor products are not warranted to be su itable for use in life-support applications, or systems. ? avantics assumes no liability for any consequence of customer product design, infringement of patents, or application assistan ce. head office: ? avantics microelectronics corp: no. 255, cai lun rd. zhangjiang technology industrial park pudong, shanghai, china tel: 86-021-58955599 fax: 86-021-58558038 a b 87 65 4 3 2 1 h i f g j k m l 1 e d c 8-lead dip-8 plastic package avantics package code: p marking: date code control code ap 3842 pb free mark pb-free: " . " (note) normal: none x note: green label is used for pb-free packing pin style: 1.comp 2.v fb 3.i sense 4.r t /c t 5.gnd 6.output 7.v i 8.v ref material: ? lead solder plating: sn60/pb40 (normal), sn/3.0ag/0.5cu or pure-tin (pb-free) ? mold compound: epoxy resin family, flammability solid burning class: ul94v-0 dim min. max. a 6.29 6.40 b 9.22 9.32 c-*1.52 d-*1.27 e-*0.99 f 3.25 3.35 g 3.17 3.55 h 0.38 0.53 i 2.28 2.79 j 7.49 7.74 k-*3.00 l 8.56 8.81 m 0.229 0.381 1 94 o 97 o *: typical, unit: mm a b f c d e g part a i h j k o m l n part a 234 5 6 7 8 pin1 index dim min. max. a 4.85 5.10 b 3.85 3.95 c 5.80 6.20 d 1.22 1.32 e 0.37 0.47 f 3.74 3.88 g 1.45 1.65 h 4.80 5.10 i 0.05 0.20 j 0.30 0.70 k 0.19 0.25 l 0.37 0.52 m 0.23 0.28 n 0.08 0.13 o 0.00 0.15 *: typical, unit: mm marking: date code control code pin 1 index as 384 pb free mark pb-free: " . " (note) normal: none 2 x note: green label is used for pb-free packing pin style: 1.comp 2.v fb 3.i sense 4.r t /c t 5.gnd 6.output 7.v i 8.v ref material: ? lead solder plating: sn60/pb40 (normal), sn/3.0ag/0.5cu or pure-tin (pb-free) ? mold compound: epoxy resin family, flammability solid burning class: ul94v-0 8-lead so-8 plastic surface mounted package avantics package code: s
page no. : 12/12 avantics - ax3842 series specification no.: 050308-fe0008 soldering methods for avantics?s products 1. storage environment: temperature=10 o c~35 o c humidity=65%15% 2. reflow soldering of surface-mount devices profile feature sn-pb eutectic assembly pb-free assembly average ramp-up rate (t l to t p )<3 o c/sec <3 o c/sec preheat - temperature min (ts min ) - temperature max (ts max ) - time (min to max) (ts) 100 o c 150 o c 60~120 sec 150 o c 200 o c 60~180 sec tsmax to t l - ramp-up rate <3 o c/sec <3 o c/sec time maintained above: - temperature (t l ) - time (t l ) 183 o c 60~150 sec 217 o c 60~150 sec peak temperature (t p ) 240 o c +0/-5 o c 260 o c +0/-5 o c time within 5 o c of actual peak temperature (t p ) 10~30 sec 20~40 sec ramp-down rate <6 o c/sec <6 o c/sec time 25 o c to peak temperature <6 minutes <8 minutes 3. flow (wave) soldering (solder dipping) products peak temperature dipping time pb devices. 245 o c 5 o c 5sec 1sec pb-free devices. 260 o c +0/-5 o c 5sec 1sec figure 1: temperature profile t p t l ramp-down ramp-up ts max ts min critical zone t l to t p t s preheat t l t p 25 t 25 o c to peak time temperature

▲Up To Search▲

Price & Availability of AX3842S

	To Download AX3842S Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .