curren t - - mode pwm controlle r the k a 3842a are fixe frequency current-mode pwm controller. they are specially designed for off - line and dc - to - dc converter applications 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 comparator, and a high current totempole output ideally suited for driving a power mosfet. protection circuity includes built under - voltage lockout and current limiting. the the k a 3842 a , ka 3 84 a m can the ka 384 2 a have start-up current 0,45 ma features low start-up current maximum duty cycle u/v lockout with hysteresis operating freguency up to 500khz ordering information device package operating temperature k a 384 2 a m s o - 8 0 to +70 0 c block diagram absolute maximum ratings characteristic symbol value unit supply voltage v cc 30 v output current i o 1 a analog inputs v i - 0.3 to v cc v error amp output sink current i sink (e.a) 10 ma power dissipation (t a =25 0 c) p o 1 w wing shing computer components co., (h.k.)ltd. tel:(852)2341 9276 fax:(852)2797 8153 homepage: http://www.wingshing.com e-mail: wsccltd@hkstar.com
electrical characteristics (*v cc =15v, r t =10k ww , c t =3.3nf, t a =0 0 c to +70 0 c, unless otherwise specified) characteristics symbol test condition min typ max unit reference section reference output voltege v ref t j = 25 c, i ref = 1 ma 4.9 5.0 5.1 v line regulation d v ref 12v v cc 25 v 6.0 20 mv load regulation d v ref 1 ma i ref 20ma 6.0 25 short circit output current i sc t a = 25 c -100 -180 ma oscillator section oscillation freguency f t j = 25 c 47 52 57 khz frequency change with voltage d f/ d v ccf 12v v cc 25 v 0.05 1.0 % oscillator amplitude v (osc) 1.6 v p -p error amplifier section input bias current i bias -0.1 -2 m a input voltage v i(e.a) v 1 = 2.5v 2.42 2.5 2.58 v open loop voltage gain g vo 2v v0 4v 65 90 db power supply rejection ratio psrr 12v v cc 25 v 60 70 output sink current i sink v 2 = 2.7v, v 1 = 1.1v 2 7 ma output source current i source v 2 = 2.3v, v 1 = 5v -0.5 -1.0 ma high output voltage v oh v 2 = 2.3v, r l = 15k w to gnd 5.0 6.0 v low output voltage v ol v 2 = 2.7v, r l = 15k w to pin 8 0.8 1.1 current sense section gain g v (note 1 & 2) 2.85 3.0 3.15 v/v maximum input signal v i(max) v 1 = 5v (note1) 0.9 1.0 1.1 v power supply rejection ratio psrr 12v v cc 25 v (note 1) 70 db input bias current i bias -3.0 -10 m a output section low output voltage v ol i sink = 20 ma 0.08 0.4 i sink = 200 ma 1.4 2.2 v high output voltage v oh i sink = 20 ma 13 13.5 i sink = 200 ma 12 13.0 rise time t r t j = 25 c, c l = 1nf (note 3) 45 150 ns fall time t f t j = 25 c, c l = 1nf (note 3) 35 150 under -- voltage lockout section start theshold v th(st) 14.5 16.0 17.5 v min. operating voltage v opr(min) 8.5 10 11.5 v (after turn on) pwm section max. duty cycle d (max) 95 97 100 % min. duty cycle d (max) 0 total standby current start - up current i st 0.17 0.3 ma operating supply current i cc (opr) v 3 = v 2 = 0v 14 17 zener voltage v z 30 38 v * adjust v cc above the start threshold before setting at 15v note 1: parameter measured at trip point of lath with v 2 =0 note 2: gain defined as a= d v 1 / d v 3 ; 0 v 3 0.8v note 3: these parameters, although guaranteed, are not 100% tested in production.
pad location chip size: 2.38 x 1.63 mm pad coordinates mm m pad coordinates mm m n x y n x y 1 90 110 5 1680 1450 2 1050 110 6 1310 1410 3 1310 110 4 2000 150 7 815 1410 8 460 1390
dim. mm inch min. typ. max. min. typ. max. a 1.75 0.069 a1 0.1 0.25 0.004 0.010 a2 1.65 0.065 a3 0.65 0.85 0.026 0.033 b 0.35 0.48 0.014 0.019 b1 0.19 0.25 0.007 0.010 c 0.25 0.5 0.010 0.020 c1 45 (typ.) d (1) 4.8 5.0 0.189 0.197 e 5.8 6.2 0.228 0.244 e 1.27 0.050 e3 3.81 0.150 f (1) 3.8 4.0 0.15 0.157 l 0.4 1.27 0.016 0.050 m 0.6 0.024 s8 (max.) (1) d and f d o not include mold flash or protrusions. mold flash or potrusions shall not exceed 0.15mm (.006inch). so8 outline and mechanical data
notes: 1. dimension l to center of lead when formed parallel. 2. package contour optional (round or square corners). 3. dimensioning and tolerancing per ansi y14.5m, 1982. 14 58 f note 2 a b t seating plane h j g d k n c l m m a m 0.13 (0.005) b m t dim min max min max inchesmillimeters a 9.40 10.16 0.370 0.400 b 6.10 6.60 0.240 0.260 c 3.94 4.45 0.155 0.175 d 0.38 0.51 0.015 0.020 f 1.02 1.78 0.040 0.070 g 2.54 bsc 0.100 bsc h 0.76 1.27 0.030 0.050 j 0.20 0.30 0.008 0.012 k 2.92 3.43 0.115 0.135 l 7.62 bsc 0.300 bsc m 10 10 n 0.76 1.01 0.030 0.040
|
