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? semiconductor components industries, llc, 2001 may, 2001 rev. 4 1 publication order number: cs2841b/d cs2841b automotive current mode pwm control circuit the cs2841b provides all the necessary features to implement offline fixed frequency currentmode control with a minimum number of external components. the cs2841b (a variation of the cs2843a) is designed specifically for use in automotive operation. the low start threshold voltage of 8.0 v (typ), and the ability to survive 40 v automotive load dump transients are important for automotive subsystem designs. the cs2841 series has a history of quality and reliability in automotive applications. the cs2841b incorporates a precision temperaturecontrolled oscillator with an internally trimmed discharge current to minimize variations in frequency. dutycycles greater than 50% are also possible. on board logic ensures that v ref is stabilized before the output stage is enabled. ion implant resistors provide tighter control of undervoltage lockout. features ? optimized for offline control ? internally trimmed temperature compensated oscillator ? maximum dutycycle clamp ? v ref stabilized before output stage 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 a = assembly location wl, l = wafer lot yy, y = year ww, w = work week device package shipping ordering information cs2841ben8 dip8 50 units/rail cs2841bed14 so14 55 units/rail cs2841bedr14 so14 2500 tape & reel dip8 n suffix case 626 pin connections and marking diagram 1 8 cs2841b awl yyww v ref v cc v out gnd comp v fb sense osc 1 8 so14 d suffix case 751a gnd osc pwr gnd nc v out sense v cc pwr nc 1 cs2841b awlyww 14 v cc v fb nc nc v ref comp 1 14 so14 dip8
cs2841b http://onsemi.com 2 figure 1. block diagram + oscillator set/ reset undervoltage lockout circuit 8.0 v/7.4 v 2.5 v 5.0 v reference internal bias output enable error amplifier v c 2 r r 1.0 v s r current sensing comparator pwm latch nor v cc gnd osc v fb comp sense v cc pwr v ref v out pwr gnd maximum ratings* rating value unit supply voltage (low impedance source) 40 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 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 seconds max. 2. 60 seconds max above 183 c *the maximum package power dissipation must be observed.
cs2841b http://onsemi.com 3 electrical characteristics (40 c t a 85 c, r t = 680 k w , c t = 0.022 m f for triangular mode, v cc = 15 v (note 3.), r t = 10 k w , c t = 3.3 nf for sawtooth mode (see figure 7); unless otherwise specified.) characteristic test conditions min typ max unit reference section output voltage t j = 25 c, i out = 1.0 ma 4.9 5.0 5.1 v line regulation 8.4 v cc 16 v 6.0 20 mv load regulation 1.0 i out 20 ma 6.0 25 mv temperature stability note 4. 0.2 0.4 mv/ c total output variation line, load, temp. note 4. 4.82 5.18 v output noise voltage 10 hz f 10 khz, t j = 25 c. note 4. 50 m v long term stability t a = 125 c, 1000 hrs. note 4. 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. see figure 7. sawtooth mode: 40 c t a +85 c triangular mode: t j =25 c. see figure 7. 47 44 44 52 52 52 57 60 60 khz khz khz voltage stability 8.4 v cc 16 v 0.2 1.0 % temperature stability sawtooth mode: t min t a t max . note 4. triangular mode: t min t a t max . note 4. 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 7.4 7.2 8.3 9.2 9.4 ma ma error amp section input voltage v comp = 2.5 v 2.42 2.5 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 4. 0.7 1.0 mhz psrr 8.4 v v cc 16 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 ground 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 5 and 6. 2.85 3.0 3.15 v/v maximum input signal v comp = 5.0 v. note 5. 0.9 1.0 1.1 v psrr 12 v v cc 25 v. note 5. 70 db input bias current v sense = 0 v 2.0 10 m a delay to output t j = 25 c. note 4. 150 300 ns 3. adjust v cc above the start threshold before setting at 15 v. 4. these parameters, although guaranteed, are not 100% tested in production. 5. parameter measured at trip point of latch with v fb = 0. 6. gain defined as: a v comp v sense ;0 v sense 0.8 v.
cs2841b http://onsemi.com 4 electrical characteristics (continued) (40 c t a 85 c, r t = 680 k w , c t = 0.022 m f for triangular mode, v cc = 15 v (note 3.), r t = 10 k w , c t = 3.3 nf for sawtooth mode (see figure 7); unless otherwise specified.) characteristic 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 7. 50 150 ns fall time t j = 25 c, c l = 1.0 nf. note 7. 50 150 ns output leakage undervoltage active, v out = 0 0.01 10 m a total standby current startup current 0.5 1.0 ma operating supply current i cc v fb = v sense = 0 v, r t = 10 k w , c t = 3.3 nf 11 17 ma undervoltage lockout section start threshold 7.6 8.0 8.4 v min. operating voltage after turn on 7.0 7.4 7.8 v 7. these parameters, although guaranteed, are not 100% tested in production. package pin description package pin # dip8 so14 pin 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 supply. 8 14 v ref output of 5.0 v internal reference. 2, 4, 6, 13 nc no connection.
cs2841b http://onsemi.com 5 typical performance characteristics figure 2. oscillator frequency vs. c t figure 3. oscillator duty cycle vs. r t 900 800 700 600 500 frequency (khz) .0005 .001 .002 .04 .05 c t ( m f) 400 300 200 100 .03 .02 .01 .003 .005 r t = 680 w r t = 1.5 k w r t = 10 k w 100 90 80 70 50 duty cycle (%) r t ( w ) 40 30 20 10 60 100 200 300 400 500 700 1 k 2 k 3 k 4 k 5 k 7 k 10 k figure 4. test circuit v ref v cc v out gnd comp v fb sense osc cs2841b r t 4.7 k w 4.7 k w 1.0 k w error amp adjust 2n2222 100 k w 5.0 k w sense adjust c t 0.1 m f 0.1 m f 1.0 k w 1.0 w a v ref v cc v out gnd
cs2841b http://onsemi.com 6 circuit description undervoltage lockout during undervoltage lockout (figure 5), the output driver is biased to a high impedance state. the output should be shunted to ground with a resistor to prevent output leakage current from activating the power switch. figure 5. typical undervoltage characteristics on/off command to reset of ic v cc v on = 8.0 v v off = 7.4 v v cc i cc 7.4 v 8.0 v < 15 ma < 1.0 ma 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 the control voltage does not have to change during changes of input supply voltage. figure 6. timing diagram for key cs2841b parameters switch current ea output v cc i o v o osc reset osc 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. figure 7. oscillator timing network and parameters internal clock triangular mode v osc v osc internal clock small r t ( 700 k w ) large r t ( 10 k w ) sawtooth mode timing parameters v upper v lower t c t d v ref osc gnd r t c t setting the oscillator oscillator timing capacitor, c t , is charged by v ref through r t and discharged by an internal current source. during the discharge time, the internal clock signal blanks out the output to the low state, thus providing a user selected maximum duty cycle clamp. charge and discharge times are determined by the general formulas:
cs2841b http://onsemi.com 7 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 t c 0.5534r t c t t d r t c t ln 2.3 0.0083r t 4.0 0.0083r t the frequency and maximum duty cycle can be determined from the typical performance characteristic graphs. grounding high peak currents associated with capacitive loads necessitate careful grounding techniques. timing and bypass capacitors should be connected close to gnd pin 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. c8 vc c10 0.1 m f 10 m f 0.1 m f c9 c13 4.7 nf osc v ref v cc pv cc v out sense comp v fb gnd pgnd r8 4.99 k 1.0 % c14 47 pf r7 22.1 k c11 0.33 m f r6 1.0 k r4 10 c12 10 nf r3 4.99 k 1.0 % mtdisn06vtl4 r9 0.2 1.0 % q2 vpr gnd q1 2n4401 dz1 13 v 1n5243b r1 4.7 k c1 68 m f 68 m f c2 c3 4.7 pf 100 v murs120t3 d1 r2 47 v cc v cc gnd 0.1 m f c7 1000 m f c5 1000 m f c6 c4 0.1 m f d2 mbr360 l1 2.2 m h 9t v cc = 5.0 v @ 750 ma r5 2.0 k cs2841b 20t figure 8. flyback application
cs2841b http://onsemi.com 8 figure 9. boost application c4 c6 0.1 m f 10 m f 0.1 m f c5 c9 470 pf osc v ref v cc v out sense comp fb gnd r8 2.0 k c8 1.0 nf r5 100 r3 10 c7 mtp12n10 r7 1.0 q1 vpr gnd 1n5818 r2 10 c1 r1 100 v d2 17 v d1 1n5818 l1 100 m h input voltage range: 8.0 v to 16 v output voltage: 17 v @ 100 ma > 300 ma r4 3.0 k cs2841b 0.01 m f r6 10 k 100 m f 12 k c3 c2 0.1 m f 330 m f
cs2841b http://onsemi.com 9 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 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 dip8 so14 unit r q jc typical 52 30 c/w r q ja typical 100 125 c/w
cs2841b http://onsemi.com 10 notes
cs2841b http://onsemi.com 11 notes
cs2841b 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 central/south america: spanish phone : 3033087143 (monfri 8:00am to 5:00pm mst) email : onlitspanish@hibbertco.com tollfree from mexico: dial 018002882872 for access then dial 8662979322 asia/pacific : ldc for on semiconductor asia support phone : 13036752121 (tuefri 9:00am to 1:00pm, hong kong time) toll free from hong kong & singapore: 00180044223781 email : onlitasia@hibbertco.com 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. cs2841b/d north america 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 fax response line: 3036752167 or 8003443810 toll free usa/canada n. american technical support : 8002829855 toll free usa/canada europe: ldc for on semiconductor european support german phone : (+1) 3033087140 (monfri 2:30pm to 7:00pm cet) email : onlitgerman@hibbertco.com french phone : (+1) 3033087141 (monfri 2:00pm to 7:00pm cet) email : onlitfrench@hibbertco.com english phone : (+1) 3033087142 (monfri 12:00pm to 5:00pm gmt) email : onlit@hibbertco.com european tollfree access*: 0080044223781 *available from germany, france, italy, uk, ireland

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