technical data 2011, february, rev. 0 3 fixed frequency current mode pwm controller description fixed frequency current - mode pwm controller. it is specially designed for off line and dc - to - dc converter applications with minimal external component. this integrated circuit featu res a trimmed oscillator for precise duty cycle control. a temperature 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 order i ng i nform ati on il 3843 n plastic il 3843d soi c t a = 0 to 70 c f or al l pack ages . device operating temperature range package il3843 n t a =0 to +70c dip - 8 il3843 d t a =0 to +70c so p - 8
il 3843 2011, february, rev. 0 3 pin function description pin no. function description 1 compensation this pln is the error am plifier 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 proporti onal 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 programmed 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 t he 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: dip - 8 sop - 8 p d 0.862 0. 625 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 * stresses beyond those listed under ?absolute maximum ratings? may cause permanent damage to the device. these are stress ratings only and functional operation of the device at these or any other condi tions beyond those indicated under ?recommended operating conditions? is not implied. exposure to absolute - maximum - rated conditions for extended periods may affect device reliability.
il 3843 2011, february, rev. 0 3 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 fr equency 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 su pply 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
il 3843 2011, february, rev. 0 3 el ectri cal characteri sti cs (v cc= 15v unl ess other wi se 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 1 5v,t a =tlow to thigh) vth 7.8 9 . 0 v minimum operating voltage after turn - on (v cc = 15 v to 0 v,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 = 6.5 v 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
il 3843 2011, february, rev. 0 3 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 no tes : l 7.62 8.26 1. dimensions ?a?, ?b? do not include mold flash or protrusions. m 0.2 0.36 maximum mold flash or protrusions 0.25 mm (0.010) per side. n 0.38 d s uffix s oic (ms - 012aa) symbol min max a 4.8 5 b 3.8 4 c 1.35 1.75 d 0.33 0.51 f 0.4 1.27 g h j 0 8 no tes : k 0.1 0.25 1. dimensions a and b do not include mold flash or protrusion. m 0.19 0.25 2. maximum mold flash or protrusion 0.15 mm (0.006) per side p 5.8 6.2 for a; for b ? 0.25 mm (0.010) per s ide. r 0.25 0.5 1.27 5.72 dimens ion, mm dimens ion, mm 2.54 7.62 a b h c k c m j f m p g d r x 45 seating plane 0.25 (0.010) m t -t- 1 8 4 5 l h m j a b f g d se ati ng plane n k 0.25 (0.010) m t -t- c 1 8 4 5
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