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? semiconductor components industries, llc, 2001 june, 2001 rev. 3 1 publication order number: cs2844/d cs2844, cs3844, cs2845, cs3845 current mode pwm control circuit with 50% max duty cycle the cs3844/45 provides all the necessary features to implement offline fixed frequency currentmode control with a minimum number of external components. the cs3844 family incorporates a new precision temperaturecontrolled oscillator to minimize variations in frequency. an internal toggle flipflop, which blanks the output every other clock cycle, limits the dutycycle range to less than 50%. an undervoltage lockout ensures that v ref is stabilized before the output stage is enabled. in the cs2844/cs3844 turn on occurs at 16 v and turn off at 10 v. in the cs2845/cs3845 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 ? temp. compensated oscillator ? 50% max dutycycle clamp ? v ref stabilized before output stage is enabled ? low startup current ? pulsebypulse current limiting ? improved undervoltage lockout ? double pulse suppression ? 1.0% trimmed bandgap reference ? high current totem pole output http://onsemi.com x = 2 or 3 y = 4 or 5 a = assembly location wl, l = wafer lot yy, y = year ww, w = work week dip8 n suffix case 626 1 8 so8 d suffix case 751 1 8 so14 d suffix case 751a 1 14 1 8 csx84yn awl yyww marking diagrams 1 384yd alyw 8 1 csx84yd14 awlyww 14 see detailed ordering and shipping information in the package dimensions section on page 7 of this data sheet. ordering information so16l dw suffix case 751g 1 16 1 csx84ydw awlyyww 16
cs2844, cs3844, cs2845, cs3845 http://onsemi.com 2 pin connections gnd osc v out sense v cc v fb v ref comp 1 pwr gnd osc gnd nc v out sense v cc pwr nc 114 v cc v fb nc nc v ref comp 8 nc nc 1 16 pwr gnd nc gnd osc v out sense v cc pwr v fb v cc comp v ref nc nc nc dip8 & so8 so14 so16l figure 1. block diagram set/ reset 5.0 v reference v cc undervoltage lockout 16 v/10 v (8.4 v/7.6 v) 34 v v cc gnd internal bias oscillator osc 2.50 v v cc pwr v ref v out + v fb comp error amplifier s r 2r r 1.0 v sense current sensing comparator pwm latch pwr gnd ( ) indicates cs2845/3845 nor v ref undervoltage lockout r r toggle flipflop
cs2844, cs3844, cs2845, cs3845 http://onsemi.com 3 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 , sense) 0.3 to + 5.5 v error amp output sink current 10 ma package thermal resistance, pdip8 junctiontocase, r q jc junctiontoambient, r q ja 52 100 cw cw package thermal resistance, so8 junctiontocase, r q jc junctiontoambient, r q ja 45 165 cw cw package thermal resistance, so14 junctiontocase, r q jc junctiontoambient, r q ja 30 125 cw cw package thermal resistance, so16l junctiontocase, r q jc junctiontoambient, r q ja 23 105 cw cw lead temperature soldering: wave solder (through hole styles only) (note 1) reflow (smd styles only) (note 2) 260 peak 230 peak c c 1. 10 second maximum. 2. 60 second maximum above 183 c. *the maximum package power dissipation must be observed. electrical characteristics (25 t a 85 for cs2844/2845, 0 t a 70 for cs3844/cs3845. v cc = 15 v*; r t = 10 k w , c t = 3.3 nf for sawtooth mode; unless otherwise stated.) cs2844/cs2845 cs3844/cs3845 characteristic test conditions min typ max min typ max unit reference section output voltage t j = 25 c, i ref = 1.0 ma 4.95 5.00 5.05 4.90 5.00 5.10 v line regulation 12 v cc 25 v 6.0 20 6.0 20 mv load regulation 1.0 i ref 20 ma 6.0 25 6.0 25 mv temperature stability note 3. 0.2 0.4 0.2 0.4 mv/ c total output variation line, load, temperature. note 3. 4.90 5.10 4.82 5.18 v output noise voltage 10 hz f 10 khz, t j = 25 c. note 3. 50 50 m v long term stability t a = 125 c, 1000 hrs. note 3. 5.0 25 5.0 25 mv output short circuit t a = 25 c 30 100 180 30 100 180 ma oscillator section initial accuracy sawtooth mode, t j = 25 c 47 52 57 47 52 57 khz voltage stability 12 v cc 25 v 0.2 1.0 0.2 1.0 % temperature stability sawtooth mode t min t a t max . note 3. 5.0 5.0 % amplitude v osc (peak to peak) 1.7 1.7 v 3. these parameters, although guaranteed, are not 100% tested in production. *adjust v cc above the start threshold before setting at 15 v.
cs2844, cs3844, cs2845, cs3845 http://onsemi.com 4 electrical characteristics (continued) (25 t a 85 for cs2844/2845, 0 t a 70 for cs3844/cs3845. v cc = 15 v*; r t = 10 k w , c t = 3.3 nf for sawtooth mode; unless otherwise stated.) cs2842a/cs2843a cs3842a/cs3843a characteristic test conditions min typ max min typ max unit error amp section input voltage v comp = 2.5 v 2.45 2.50 2.55 2.42 2.50 2.58 v input bias current v fb = 0 0.3 1.0 0.3 2.0 m a a vol 2.0 v out 4.0 v 65 90 65 90 db unity gain bandwidth note 4. 0.7 1.0 0.7 1.0 mhz psrr 12 v cc 25 v 60 70 60 70 db output sink current v fb = 2.7 v, v comp = 1.1 v 2.0 6.0 2.0 6.0 ma output source current v fb = 2.3 v, v comp = 5.0 v 0.5 0.8 0.5 0.8 ma v out high v fb = 2.3 v, r l = 15 k w to gnd 5.0 6.0 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 0.7 1.1 v current sense section gain notes 5 & 6. 2.85 3.00 3.15 2.85 3.00 3.15 v/v maximum input signal v comp = 5.0 v. note 5. 0.9 1.0 1.1 0.9 1.0 1.1 v psrr 12 v cc 25 v. note 5. 70 70 db input bias current v sense = 0 2.0 10 2.0 10 m a delay to output t j = 25 c. note 4. 150 300 150 300 ns output section output low level i sink = 20 ma i sink = 200 ma 0.1 1.5 0.4 2.2 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 13 12 13.5 13.5 v v rise time t j = 25 c, c l = 1.0 nf. note 4. 50 150 50 150 ns fall time t j = 25 c, c l = 1.0 nf. note 4. 50 150 50 150 ns total standby current startup current 0.5 1.0 0.5 1.0 ma operating supply current v fb = v sense = 0 v, r t = 10 k w , c t = 3.3 nf 11 17 11 17 ma v cc zener voltage i cc = 25 ma 34 34 v pwm section maximum duty cycle 46 48 50 46 48 50 % minimum duty cycle 0 0 % 4. these parameters, although guaranteed, are not 100% tested in production. 5. parameters measured at trip point of latch with v fb = 0. 6. gain defined as: a = d v comp / d v sense ; 0 v sense 0.8 v. *adjust v cc above the start threshold before setting at 15 v.
cs2844, cs3844, cs2845, cs3845 http://onsemi.com 5 electrical characteristics (continued) (25 t a 85 for cs2844/2845, 0 t a 70 for cs3844/cs3845. v cc = 15 v*; r t = 10 k w , c t = 3.3 nf for sawtooth mode; unless otherwise stated.) cs2844 cs3844 cs2845/cs3845 characteristic test conditions min typ max min typ max min typ max unit undervoltage lockout section start threshold 15 16 17 14.5 16 17.5 7.8 8.4 9.0 v min. operating voltage after turn on 9.0 10 11 8.5 10 11.5 7.0 7.6 8.2 v *adjust v cc above the start threshold before setting at 15 v. package pin description package pin number dip8 & so8 so14 symbol symbol description 1 1 3 comp error amp output, used to compensate error amplifier. 2 3 4 v fb error amp inverting input. 3 5 5 sense noninverting input to current sense comparator. 4 7 6 osc oscillator timing network with capacitor to ground, resistor to v ref. 5 9 11 gnd ground. 8 10 pwr gnd output driver ground. 6 10 12 v out output drive pin. 11 13 v cc pwr output driver positive supply. 7 12 14 v cc positive power supply. 8 14 15 v ref output of 5.0 v internal reference. 2, 4, 6, 13 1, 2, 7, 8, 9, 16 nc no connection. figure 2. test circuit open loop laboratory test fixture v ref v cc v out gnd comp v fb sense osc 0.1 m f 0.1 m f r t 1.0 k w 1.0 w 2n2222 100 k w v cc v ref v out gnd a 5.0 k w sense adjust c t 4.7 k w 4.7 k w 1.0 k w error amp adjust
cs2844, cs3844, cs2845, cs3845 http://onsemi.com 6 circuit description csx845 8.4 v 7.6 v csx844 16 v 10 v v on v off on/off command to reset of ic v cc < 1.0 ma < 15 ma v on v off v cc i cc figure 3. startup voltage for csx844 and csx845 undervoltage lockout during undervoltage lockout (figure 3), 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 4). 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 the control voltage does not have to change during changes of input supply voltage. figure 4. timing diagram v osc osc reset toggle f/f output ea output switch current v cc i o v o figure 5. duty cycle parameters v upper v lower t on t c t off t d t on = t c t off = t c + 2t d 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 osc components. 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.
cs2844, cs3844, cs2845, cs3845 http://onsemi.com 7 ordering information device temperature range package shipping cs2844ln8 dip8 50 units/rail cs2844ld14 so14 55 units/rail cs2844ldr14 so14 2500 tape & reel cs2844ldw16 25 cto85 c so16l 48 units/rail cs2844ldwr16 25 c to 85 c so16l 2500 tape & reel cs2845ln8 dip8 50 units/rail cs2845ldw16 so16l 48 units/rail cs2845ldwr16 so16l 2500 tape & reel cs3844gn8 dip8 50 units/rail cs3844gd8 so8 98 units/rail cs3844gdr8 so8 2500 tape & reel cs3844gd14 so14 55 units/rail cs3844gdr14 so14 2500 tape & reel cs3844gdw16 so16 48 units/rail cs3844gdwr16 0 cto70 c so16 2500 tape & reel cs3845gn8 0 c to 70 c dip8 50 units/rail cs3845gd8 so8 98 units/rail cs3845gdr8 so8 2500 tape & reel cs3845gd14 so14 55 units/rail cs3845gdr14 so14 2500 tape & reel cs3845gdw16 so16l 48 units/rail cs3845gdwr16 so16l 2500 tape & reel
cs2844, cs3844, cs2845, cs3845 http://onsemi.com 8 package dimensions dip8 n suffix case 62605 issue l 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 5 8 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 inches millimeters 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 so8 d 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
cs2844, cs3844, cs2845, cs3845 http://onsemi.com 9 package dimensions 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 so16l dw suffix case 751g03 issue b d 14x b 16x seating plane s a m 0.25 b s t 16 9 8 1 h x 45 m b m 0.25 h 8x e b a e t a1 a l c notes: 1. dimensions are in millimeters. 2. interpret dimensions and tolerances per asme y14.5m, 1994. 3. dimensions d and e do not inlcude mold protrusion. 4. maximum mold protrusion 0.15 per side. 5. dimension b does not include dambar protrusion. allowable dambar protrusion shall be 0.13 total in excess of the b dimension at maximum material condition. dim min max millimeters a 2.35 2.65 a1 0.10 0.25 b 0.35 0.49 c 0.23 0.32 d 10.15 10.45 e 7.40 7.60 e 1.27 bsc h 10.05 10.55 h 0.25 0.75 l 0.50 0.90 0 7
cs2844, cs3844, cs2845, cs3845 http://onsemi.com 10 notes
cs2844, cs3844, cs2845, cs3845 http://onsemi.com 11 notes
cs2844, cs3844, cs2845, cs3845 http://onsemi.com 12 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. cs2844/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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