technical data rev. 01 fixed frequency current mode pwm controller description fixed frequency current-mode pwm cont roller. it is specially designed for off line and dc-to-dc converter applications with minimal external component. this integrated circuit features a trimmed oscillator for precise duty cycle control. a temper ature compensated reference, high gain arror amplifier, current sensing comparator, and a high current totempole output ideally suited for driving a power mosfet. protection circuitry includes built in under-voltage lockout and current limiting . features ? automatic feed forward compensation ? high gain totem pole output ? internally trimmed bandgap reference ? undervoltage lockout with hysteresis ? low start up current ? optimized for offline converter ? double pulse suppression ? current mode operation to 500khz ordering information IL3843 device operating temperature range package IL3843 t a =0 to +70c dip-8
IL3843 rev. 01 pin function description pin no. function description 1 compensation this pln is the error amplifier output and is made available for loop compensation 2 voltage feedback this is the inverting input of the error amplifier. it is normally connected to the switching power supply outpul through a resistor divider. 3 current sense a voltage proportional to inductor current is connected to this input. the pwm uses this. information to terminate the output switch conduction 4 rt/ct the oscillator frequency and maximum output duty cycle are progr ammed by connecting resistor r t to v ref and capacitor c t to ground. operation to 500khz is possible. 5 gnd this pin is the combined conlrol circuitry and power ground 6 output this output directly drives the gate of a power mosfet. peak currents up to 1,0a are sourced and sunk by this pin. 7 vcc this pin is the positive supply of the control ic. 8 v ref this is the reference output. it provides chsarging current for capacitor c t through resistor r t absolute maximum ratings characteristic symbol value unit total power supply and zener current (i cc + i z ) 30 ma output current i o 1.0 a output energy (capacitive load per cycle) w 5.0 j error amp output sink current i oe 10 ma current sense and voltage feedback inputs vin -0.3 to 5.5 v maximum power dissipation @ t a = 25 o c: p d 0.862 w thermal resistance,junction-to-air r ja 145 c/w operating junction temperature t j +150 o c storage temperature range t stg -65 ~ +150 o c
IL3843 rev. 01 electrical characteristics (vcc=15v unless otherwise noted) characteristics symbol min max unit reference section reference output voltage (i o =1.0ma, v cc =15v , t a =25 10c) (i o =1.0ma, v cc =15v , t a = tlow to thigh) v ref 4.9 4.865 5.1 5.135 v line regulation (v cc =12v to 25v,t a =tlow to thigh) reg line 20 mv load regulation (i o =1.0 to 20ma,t a =tlow to thigh) reg load 25 mv total output variation over line,load,temperature (note1) (v cc =12v, i o =1.0ma,t a =tlow to thigh) (v cc =25v, i o =20ma,t a =tlow to thigh) vfinal 4.82 5.18 v output short circuit current (v cc =15v) i sc -30 -180 ma oscillator section frequency (v cc =15v,tj=25c,r t =10k,c t =3.3nf) (v cc =15v, t a =tlow to thigh,r t =10k,c t =3.3nf) f osc 47 46 57 60 khz frequency change with voltage (v cc =12v to 25v, t a =tlow to thigh,r t =10k,c t =3.3nf) ? f osc / ? v 1.0 % discharge current (vosc=2.0v, v cc =15v) tj=25c t a =tlow to thigh idisch 7.5 7.2 9.3 9.5 ma error amplifier section voltage feedback input (v o =2.5v,v cc =15v, t a =tlow to thigh) v fb 2.42 2.58 v input bias current (v fb =2.7v,v cc =15v, t a =tlow to thigh) i ib -2.0 a open loop voltage gain (v o =2.0v to 4.0v,v cc =15v, t a =tlow to thigh) a vol 65 db unity gain bandwidth (v cc =15v, t a =tlow to thigh) bw 0.7 mhz power supply rejection ratio (v cc =12v to 25v, vo=3.0v, t a =tlow to thigh) psrr 60 db output current sink (v o =1.1v,v fb =2.7v, v cc =15v, t a =tlow to thigh) source (v o =5.0v,v fb =2.3v, v cc =15v, t a =tlow to thigh) i sink i source 2.0 -0.5 ma output voltage swing high state (v fb =2.3v, v cc =15v,r l(gnd) =15k, t a =tlow to thigh) low state (v fb =2.7v, v cc =15v,r l(5.0) =15k, t a =tlow to thigh) v oh v ol 5.0 1.1 v current sense section current sense input voltage gain (v fb =0v, v cc =15v, t a =tlow to thigh) av 2.85 3.15 v/v maximum current sense input threshold (v fb =0v, v cc =15v, t a =tlow to thigh) vth 0.9 1.1 v input bias current (v cc =15v, t a =tlow to thigh) i ib -10 a propagation delay (current sense input to output) (v cc =15v, t a =tlow to thigh) t plh 300 ns
IL3843 rev. 01 electrical characteristics (vcc=15v unless otherwise noted) characteristics symbol min max unit output section output voltage low state (sink=20ma, v cc =15v) (sink=200ma, v cc =15v) high state (sink=-20ma, v cc =15v) (sink=-200ma, v cc =15v) v ol v oh 13 12 0.4 2.2 v output voltage with uvlo activated (v cc =6.0v, i sink ,=1.0ma, t a =tlow to thigh) v ol(uvl o) 1.1 v output voltage rise time (c l =1.0nf, v cc =15v, t a =tlow to thigh) tr 150 ns output voltage fall time (c l =1.0nf, v cc =15v, t a =tlow to thigh) tf 150 ns ondervoltage lockout section startup threshold (v cc =0v to 15v,t a =tlow to thigh) vth 7.8 9.0 v minimum operating voltage after turn-on (v cc =15v to 0v,t a =tlow to thigh) v cc(min) 7.0 8.2 v pwm section duty cycle maximum (v cc =15v, t a =tlow to thigh,r t =10k,c t =3.3nf) minimum (v cc =15v, t a =tlow to thigh,r t =10k,c t =3.3nf) dcmax dcmin 94 0 % total device power supply current startup: v cc =6.5v v cc =15v operating i cc 1.0 17 ma power supply zener voltage (i cc =25ma, v cc =0 to 40v) vz 30 40 v notes: 1 . vfinal= v ref25 ( reg line + reg load )/1000 | v ref70 (v ref0 )-v ref25 | v ref25 =vref @ t a =25c; v ref70 =vref @ t a =70c; v ref0 =vref @ t a =0c. 2. tlow= 0c ; thigh=+70c
IL3843 rev. 01 n suffix plastic dip (ms ? 001ba) symbol min max a 8.51 10.16 b 6.1 7.11 c 5.33 d 0.36 0.56 f 1.14 1.78 g h j 0 10 k 2.92 3.81 notes: l 7.62 8.26 1. dimensions ?a?, ?b? do not include mold flash or protrusions. m 0.2 0.36 maximum mold flas h or protrus ions 0.25 mm (0.010) per s ide. n 0.38 dimension, mm 2.54 7.62 l h m j a b f g d seating plane n k 0.25 (0.010) m t -t- c 1 8 4 5
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