? semiconductor components industries, llc, 2001 may, 2001 rev. 3 1 publication order number: cs52843/d cs52843 current mode pwm control circuit the cs52843 provides all the necessary features to implement offline fixed frequency currentmode control with a minimum number of external components. the cs52843 incorporates a new precision temperaturecontrolled oscillator to minimize variations in frequency. an undervoltage lockout ensures that v ref is stabilized before the output stage is enabled. in the cs52843 turn on is at 8.4 v and turn off at 7.6 v. other features include low startup current, pulsebypulse current limiting, and a highcurrent totem pole output for driving capacitive loads, such as gate of a power mosfet. the output is low in the off state, consistent with nchannel devices. features ? optimized for offline control ? internally temperature compensated oscillator ? v ref stabilized before output stage is enabled ? very low startup current 300 m a (typ) ? pulsebypulse current limiting ? improved undervoltage lockout ? double pulse suppression ? 2.0% 5.0 volt reference ? high current totem pole output http://onsemi.com a = assembly location wl, l = wafer lot yy, y = year ww, w = work week pin connections and marking diagrams so8 d suffix case 751 v ref comp 52843 1 v fb sense osc v cc v out gnd alywx device package shipping ordering information cs52843ed8 so8 95 units/rail cs52843edr8 so8 cs52843ed14 so14 2500 tape & reel cs52843edr14 so14 2500 tape & reel 55 units/rail 1 8 so14 d suffix case 751a gnd osc pwr gnd nc v out sense v cc pwr nc 1 cs52843 awlyww 14 v cc v fb nc nc v ref comp 1 14
cs52843 http://onsemi.com 2 v out pwr gnd v ref gnd v cc figure 1. block diagram + v cc pwr internal bias nor output enable s r current sensing comparator 1.0 v r 2r oscillator 2.50 v r r error amplifier 8.4 v/7.6 v 34 v v cc undervoltage lockout set/ reset 5.0 volt reference pwm latch v fb comp osc sense maximum ratings* rating value unit supply voltage (i cc < 30 ma) self limiting supply voltage (low impedance source) 30 v output current 1.0 a output energy (capacitive load) 5.0 m j analog inputs (v fb , v sense ) 0.3 to 5.5 v error amp output sink current 10 ma lead temperature soldering: reflow: (smd styles only) (note 1) 230 peak c 1. 60 second maximum above 183 c. *the maximum package power dissipation must be observed.
cs52843 http://onsemi.com 3 electrical characteristics (40 c t a 85 c; v cc = 15 v (note 2.); r t = 680 w; c t = 0.022 m f for triangle mode, r t = 10 k w; c t = 3.3 nf sawtooth mode; unless otherwise specified.) parameter test conditions min typ max unit reference section output voltage t j = 25 c, i ref = 1.0 ma 4.9 5.0 5.1 v line regulation 12 v cc 25 v 6.0 20 mv load regulation 1.0 i ref 20 ma 6.0 25 mv temperature stability note 2. 0.2 0.4 mv/ c total output variation line, load, temp. note 2. 4.82 5.18 v output noise voltage 10 hz f 10 khz, t j = 25 c, note 2. 50 m v long term stability t a = 125 c, 1000 hrs. note 2. 5.0 25 mv output short circuit t a = 25 c 30 100 180 ma oscillator section initial accuracy sawtooth mode, t j = 25 c, note 2. triangle mode, t j = 25 c 47 44 52 52 57 60 khz khz voltage stability 12 v cc 25 v 0.2 1.0 % temperature stability sawtooth mode t min t a t max triangle mode t min t a t max, note 2. 5.0 8.0 % % amplitude v osc (peak to peak) 1.7 v discharge current t j = 25 c t min t a t max 7.3 6.8 8.3 9.3 9.8 ma ma error amp section input voltage v comp = 2.5 v 2.42 2.50 2.58 v input bias current v fb = 0 v 0.3 2.0 m a a vol 2.0 v out 4.0 v 65 90 db unity gain bandwidth note 2. 0.7 1.0 mhz psrr 12 v cc 25 v 60 70 db output sink current v fb = 2.7 v, v comp = 1.1 v 2.0 6.0 ma output source current v fb = 2.3 v, v comp = 5.0 v 0.5 0.8 ma v out high v fb = 2.3 v, r l = 15 k w to gnd 5.0 6.0 v v out low v fb = 2.7 v, r l = 15 k w to v ref 0.7 1.1 v current sense section gain notes 3 & 4. 2.85 3.0 3.15 v/v maximum input signal v comp = 5.0 v, note 3. 0.9 1.0 1.1 v psrr 12 v cc 25 v, note 3. 70 db input bias current v sense = 0 v 2.0 10 m a delay to output t j = 25 c, note 2. 150 300 ns 2. these parameters, although guaranteed, are not 100% tested in production. 3. parameter measured at a trip point of latch with v fb = 0. 4. gain defined as: a v comp v sense ;0 v sense 0.8 v
cs52843 http://onsemi.com 4 electrical characteristics (continued) (40 c t a 85 c; v cc = 15 v (note 2.); r t = 680 w; c t = 0.022 m f for triangle mode, r t = 10 k w; c t = 3.3 nf sawtooth mode; unless otherwise specified.) parameter unit max typ min test conditions output section output low level i sink = 20 ma i sink = 200 ma 0.1 1.5 0.4 2.2 v v output high level i source = 20 ma i source = 200 ma 13 12 13.5 13.5 v v rise time t j = 25 c, c l = 1.0 nf, note 5. 50 150 ns fall time t j = 25 c, c l = 1.0 nf, note 5. 50 150 ns output leakage uvlo active v out = 0 0.01 10 m a total standby current startup current 300 500 m a operating supply current v fb = v sense = 0 v, r t = 10 k w; c t = 3.3 nf 11 17 ma v cc zener voltage i cc = 25 ma 34 v undervoltage lockout section start threshold 7.8 8.4 9.0 v min. operating voltage after turn on 7.0 7.6 8.2 v 5. these parameters, although guaranteed, are not 100% tested in production. package pin description package lead number so8 so14 lead symbol function 1 1 comp error amp output, used to compensate error amplifier. 2 3 v fb error amp inverting input. 3 5 sense noninverting input to current sense comparator. 4 7 osc oscillator timing network with capacitor to ground, resistor to v ref. 5 8 gnd ground. 9 pwr gnd output driver ground. 6 10 v out output drive pin. 11 v cc pwr output driver positive supply. 7 12 v cc positive power suppy. 8 14 v ref output of 5.0 v internal reference. 2, 4, 6, 13 nc no connection.
cs52843 http://onsemi.com 5 typical performance characteristics 900 frequency (khz) 800 700 600 500 400 300 200 100 .0005 .001 .002 .003 .005 .01 .02 .03 .04 .05 c t ( m f) duty cycle (%) 100 90 80 70 60 50 40 30 20 10 r t ( w ) figure 2. oscillator frequency vs c t figure 3. oscillator duty cycle vs r t 100 200 300 400 500 700 1 k 2 k 3 k 4 k 5 k 10 k 7 k r t = 680 w r t = 1.5 k w r t = 10 k w v ref comp v cc v out gnd v fb sense osc c t v ref v cc v out gnd a 0.1 m f 0.1 m f 1.0 k w 2n2222 r t 100 k w 5.0 k w sense adjust 4.7 k w 1.0 k w error amp adjust 4.7 k w figure 4. test circuit open loop laboratory test fixture 1.0 w circuit description figure 5. startup voltage for the cs52843 v on = 8.4 v on/off command to reset of ic i cc v cc v off = 7.6 v v on v off v cc < 15 ma < 500 m a undervoltage lockout during undervoltage lockout (figure 5), the output driver is biased to sink minor amounts of current. the output should be shunted to ground with a resistor to prevent activating the power switch with extraneous leakage currents. pwm waveform to generate the pwm waveform, the control voltage from the error amplifier is compared to a current sense signal which represents the peak output inductor current (figure 6). an increase in v cc causes the inductor current slope to increase, thus reducing the duty cycle. this is an inherent feedforward characteristic of current mode control, since
cs52843 http://onsemi.com 6 the control voltage does not have to change during changes of input supply voltage. when the power supply sees a sudden large output current increase, the control voltage will increase allowing the duty cycle to momentarily increase. since the duty cycle tends to exceed the maximum allowed to prevent transformer saturation in some power supplies, the internal oscillator waveform provides the maximum duty cycle clamp as programmed by the selection of oscillator timing components. figure 6. timing diagram v osc osc reset toggle f/f output ea output switch current v cc i o v o setting the oscillator the times t c and t d can be determined as follows: t c r t c t ln v ref v lower v ref v upper t d r t c t ln v ref i d r t v lower v ref i d r t v upper substituting in typical values for the parameters in the above formulas: v ref 5.0 v, v upper 2.7 v, v lower 1.0 v, i d 8.3 ma then t c 0.5534r t c t t d r t c t ln 2.3 0.0083r t 4.0 0.0083r t for better accuracy r t should be 10 k w . grounding high peak currents associated with capacitive loads necessitate careful grounding techniques. timing and bypass capacitors should be connected close to gnd in a single point ground. the transistor and 5.0 k w potentiometer are used to sample the oscillator waveform and apply an adjustable ramp to sense. figure 7. oscillator timing network and parameters v in r t c t v ref internal clock v osc internal clock large r t ( 10 k w ) sawtooth mode triangular mode small r t ( 700 w ) v upper v lower t c t d osc v ref gnd
cs52843 http://onsemi.com 7 package dimensions so8 df suffix case 75107 issue w seating plane 1 4 5 8 n j x 45 k notes: 1. dimensioning and tolerancing per ansi y14.5m, 1982. 2. controlling dimension: millimeter. 3. dimension a and b do not include mold protrusion. 4. maximum mold protrusion 0.15 (0.006) per side. 5. dimension d does not include dambar protrusion. allowable dambar protrusion shall be 0.127 (0.005) total in excess of the d dimension at maximum material condition. a b s d h c 0.10 (0.004) dim a min max min max inches 4.80 5.00 0.189 0.197 millimeters b 3.80 4.00 0.150 0.157 c 1.35 1.75 0.053 0.069 d 0.33 0.51 0.013 0.020 g 1.27 bsc 0.050 bsc h 0.10 0.25 0.004 0.010 j 0.19 0.25 0.007 0.010 k 0.40 1.27 0.016 0.050 m 0 8 0 8 n 0.25 0.50 0.010 0.020 s 5.80 6.20 0.228 0.244 x y g m y m 0.25 (0.010) z y m 0.25 (0.010) z s x s m so14 d suffix case 751a03 issue f notes: 1. dimensioning and tolerancing per ansi y14.5m, 1982. 2. controlling dimension: millimeter. 3. dimensions a and b do not include mold protrusion. 4. maximum mold protrusion 0.15 (0.006) per side. 5. dimension d does not include dambar protrusion. allowable dambar protrusion shall be 0.127 (0.005) total in excess of the d dimension at maximum material condition. a b g p 7 pl 14 8 7 1 m 0.25 (0.010) b m s b m 0.25 (0.010) a s t t f r x 45 seating plane d 14 pl k c j m dim min max min max inches millimeters a 8.55 8.75 0.337 0.344 b 3.80 4.00 0.150 0.157 c 1.35 1.75 0.054 0.068 d 0.35 0.49 0.014 0.019 f 0.40 1.25 0.016 0.049 g 1.27 bsc 0.050 bsc j 0.19 0.25 0.008 0.009 k 0.10 0.25 0.004 0.009 m 0 7 0 7 p 5.80 6.20 0.228 0.244 r 0.25 0.50 0.010 0.019 package thermal data parameter so8 so14 unit r q jc typical 45 30 c/w r q ja typical 165 125 c/w
cs52843 http://onsemi.com 8 on semiconductor and are trademarks of semiconductor components industries, llc (scillc). scillc reserves the right to make changes without further notice to any products herein. scillc makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does scillc assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages. atypicalo parameters which may be provided in scill c data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. all operating parameters, including atypicalso must be validated for each customer application by customer's technical experts. scillc does not convey any license under its patent rights nor the rights of others. scillc products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body , or other applications intended to support or sustain life, or for any other application in which the failure of the scillc product could create a sit uation where personal injury or death may occur. should buyer purchase or use scillc products for any such unintended or unauthorized application, buyer shall indemnify and hold scillc and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthori zed use, even if such claim alleges that scillc was negligent regarding the design or manufacture of the part. scillc is an equal opportunity/affirmative action employer. publication ordering information japan : on semiconductor, japan customer focus center 4321 nishigotanda, shinagawaku, tokyo, japan 1410031 phone : 81357402700 email : r14525@onsemi.com on semiconductor website : http://onsemi.com for additional information, please contact your local sales representative. cs52843/d literature fulfillment : literature distribution center for on semiconductor p.o. box 5163, denver, colorado 80217 usa phone : 3036752175 or 8003443860 toll free usa/canada fax : 3036752176 or 8003443867 toll free usa/canada email : onlit@hibbertco.com n. american technical support : 8002829855 toll free usa/canada
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