1 cs3972 1.25a high efficiency switching regulator cs3972 description block diagram features 75v max , 2a peak internal switch 3v to 60v input voltage range 6ma input supply current 1.24v precision reference 40khz switching frequency variable current limit with external voltage clamp under-voltage protection over-temperature protection external synchronization package options 5l to-220 tab (gnd) 8l pdip 1 gnd v c v fb nc e 2 v sw e 1 v in 1 1v c 2v fb 3 gnd 4v sw 5v in 16l so wide 1 gnd nc nc nc nc v in e 1 v sw e 2 v c v fb nc nc nc nc nc december, 2001 - rev. 9 on semiconductor 2000 south county trail, east greenwich, ri 02818 tel: (401)885?600 fax: (401)885?786 n. american technical support: 800-282-9855 web site: www.cherry?emi.com archive device not recommended for new design the cs3972 is a 1.25a, 60v, current mode, high efficiency, switching regulator circuit. it can be config- ured in buck, boost, forward, iso- lated and non-isolated topologies, using a single-ended switch. the ic contains a 1.25a high effi- ciency output switch, precision bandgap reference, voltage regula- tor, error amplifier, oscillator, con- trol, and protection circuitry. output transistor efficiency is achieved by keeping the switch in quasi-saturation when it is on. this minimizes the switch turn-off delay time and power dissipation, an important consideration for applications with wide ranging loads. the precision reference is internally trimmed to 1.24v, while the oscilla- tor frequency is internally trimmed to 40khz. the on board 2.3v regu- lator powers the internal circuitry. by keeping the voltage regulator at 2.3v, the ic is able to operate down to 3v and maintain a constant input supply current of 6ma(typ). synchronization mode is achieved by applying a pulsating v c voltage of less than 0.2v with a duration of about 0.5 s to v c pin. the switch- ing frequency can be adjusted from 50khz to 70khz. the ic's synchro- nization mode is set externally. protection circuitry includes a vari- able current limit with external voltage clamp, under-voltage and over-temperature protection. output protection driver 2.3v reg logic 40khz osc error amp - + 1.24v ref current amp - + v sw v c v in v fb 0.22 ? 0.22 ? comp e 1 * e 2 * gnd *always connect e1 to ground pin on dip package. both emitters are tied to ground on to-220 package. 1.25a, 75v switch - +
2 absolute maximum ratings cs3972 parameter test conditions min typ max unit input voltage range ............................................................................................................ ............................................3v to 60v output switching voltage....................................................................................................... ..................................................75v voltage transient (t r =10 s, t f =400ms) ........................................................................................................................ ..............60v esd (human body model; r=1.5k ? , c=100pf) ...................................................................................................................2k v junction temperature range..................................................................................................... ..........................-40? to +150? storage temperature range ...................................................................................................... ..........................-65? to +150? lead temperature soldering wave solder (through hole styles only)......................................................................................10 sec. max, 260? peak reflow (smd styles only) ......................................................................................60 sec. max above 183?, 230? peak feedback pin voltage (1ms transient)........................................................................................... ........................................ 15v electrical characteristics: for 3v v cc 60v, -40? t a 125? unless otherwise specified. reference voltage v c =0.8v; v fb =v ref 1.214 1.244 1.274 v line regulation v c =0.8v; v fb =v ref , 3v v in 60v 0.03 %/v feedback input current v c =0.8v; v fb =v ref 350 1100 na minimum input voltage v c =v fb =v ref 2.6 3.0 v supply current v c =0.6v; 3v v in 60v 6.0 9.0 ma supply current increase during switch on time v c =open, 1.0v v fb 1.5v 25 ma/a switching frequency v c =v fb =v ref; v sw =15v 33 40 47 khz maximum duty cycle v c =2v; v fb =open, v sw =15v 92 % v c threshold v fb =open; v sw =15v, 0.60 0.90 1.25 v duty cycle=0% error amplifier transconductance v c =0.8v; v fb =v ref , ? i c = 25 a 2400 4400 7000 mho source/sink current v c =1.5v 120 200 400 a high voltage clamp v fb =1.0v 2.0 v low voltage clamp v fb =1.5v 0.38 v gain 0.9v v c 1.4v, v fb =v ref 800 v/v output switch breakdown voltage v c =0.5v; 3v v in 60v, i out =5ma 75 90 v on resistance v c =open, v fb =0.8v, i out =1.25a 0.6 1.0 ? control voltage to switch 1.2v v c 1.8v 2 a/v current transconductance current limit duty cycle 50%, t j 25? 1.25 3.00 a duty cycle 50%, t j <25? 1.25 3.50 a duty cycle=80% 1.00 2.50 a duty cycle=80% (note 1) 0.50 2.50 a note 1: 16 lead so wide package only.
3 package pin description package pin # pin symbol function typical performance characteristics 1.274 1.264 1.254 1.244 1.234 1.224 1.214 -50 -25 -0 25 50 75 100 125 150 temperature ( c) reference voltage (v) reference voltage vs. temperature 47 45 43 41 39 37 33 -50 -25 -0 25 50 75 100 125 150 temperature ( c) frequency (khz) 35 switching frequency vs. temperature 100 90 80 70 60 50 0 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 switch current (a) driver current (ma) 10 40 30 20 1.8 2.0 driver current vs. switch current 97 96 95 93 92 91 90 -50 -25 -0 25 50 75 100 125 150 junction temperature ( c) duty cycle (%) maximum duty cycle 1.6 1.4 1.2 1.0 0.8 0.6 0 0 0.50 1.00 1.25 1.75 switch current (a) switch saturation voltage (v) 0.4 0.2 2.0 0.25 0.75 1.50 t j =25 c switch saturation voltage 16l 5l 8l so wide to-220 pdip 16 3 1 gnd logic and power ground on to-220. logic ground only on 8l pdip. 21 2 v c control voltage can be used for frequency compensation, cur- rent limit threshold, frequency synchronization, and soft start. 32 3 v fb feedback voltage is the negative input to the error amplifier. 1,4,5,6,7,8, 4 nc no connection. 10,12,15 95 5 v in supply input voltage with a range of 3v to 60v. 11 6 e 1 emitter one is a power ground which should always be con- nected to logic ground since it is used as the negative input to the current sense amp. 13 4 7 v sw collector of internal 75v npn power switch. 14 8 e 2 emitter two is a power ground which can be left disconnected to reduce the switch rating to 625ma. cs3972
the cs3972 has an on board, high current npn transistor in its output stage. the output transistor is switched on every 25 s by the on board 40 khz oscillator. the output is switched off as soon as the output current reaches a dynamically controlled level. that level is determined by three factors: the current drawn by the load, the input voltage, and the output voltage. this control scheme has several benefits. the ic reacts quickly to overvoltage and short circuit conditions and it is less sensitive to input voltage fluctuation. current drawn by the load influences when the output stage turns off. the voltage across the internal high preci- sion resistor (0.11 ? ) in the emitter of the output transistor generating the input to the current sensing amplifier. the output of the current sensing amplifier provides one of the inputs to the comparator. the other input to the comparator connected to the out- put of the error amplifier whose inverting input is con- nected to the output voltage through the feedback circuit- ry while its noninverting input is set to an internal refer- ence voltage of 1.24v. when the current sensing amplifier output exceeds the error amplifier output, the comparator switches off, triggering the logic which turns off the out- put stage. all on board amplifier, logic and protection circuitry uses the internal 2.3v reference to minimize quiescent current drain (6ma) and permits ic operation down to 3v. the anti-saturation circuitry minimizes output switch turn off time and power dissipation, by keeping the power npn at the edge of saturation. 4 circuit description application diagrams v in d 1 c 1 + r 1 c 2 r 3 c 3 (1.24v) r 2 v out v in v c gnd v fb v sw cs3972 l 1 + v in q 1 r 1 c 1 + r 2 c 2 d 1 r 4 c 3 (1.24v) r 3 v out v in v c gnd v fb v sw cs3972 l 1 + v in tr 1 r 1 c 2 + r 2 c 3 r 5 (1.24v) r 4 v out 1 v in v c gnd v fb v sw cs3972 c 4 c 1 c 5 + c 6 + v out 2 +v in tr 1 c 2 + r 2 c 3 r 7 r 5 v out v in v c gnd v fb v sw cs3972 c 3 + c 5 l 1 d 2 d 1 r 4 1/2 oc1 r 6 c 4 u 1 r 3 d 1 r 1 ? in d 3 1/2 oc1 figure 1: boost regulator figure 2: buck regulator with the external switch figure 3: flyback multiple output regulator figure 4: isolated forward regulator cs3972
thermal data 5l 8l 16l to-220 pdip so wide r jc typ 1.7 52 23 ?/w r ja typ 50 100 105 ?/w d lead count metric english max min max min 8 lead pdip 10.16 9.02 .400 .355 16 lead so wide 10.50 10.10 .413 .398 5 cs3972 package specification package dimensions in mm (inches) package thermal data plastic dip (n); 300 mil wide 0.39 (.015) min. 2.54 (.100) bsc 1.77 (.070) 1.14 (.045) d some 8 and 16 lead packages may have 1/2 lead at the end of the package. all specs are the same. .203 (.008) .356 (.014) ref: jedec ms-001 3.68 (.145) 2.92 (.115) 8.26 (.325) 7.62 (.300) 7.11 (.280) 6.10 (.240) .356 (.014) .558 (.022) surface mount wide body (dw); 300 mil wide 1.27 (.050) bsc 7.60 (.299) 7.40 (.291) 10. 65 (.41 9 ) 10. 00 (. 394 ) d 0.32 (.013) 0.23 (.009) 1.27 (.050) 0.40 (.016) ref: jedec ms-013 2.49 (.098) 2.24 (.088) 0.51 (.020) 0.33 (.013) 2.65 (.104) 2.35 (.093) 0.30 (.012) 0.10 (.004)
6 package specification ordering information cs3972 part number description cs3972yn8 8l pdip cs3972ydw16 16l so wide cs3972ydwr16 16l so wide (tape & reel) cs3972yt5 to-220 straight on semiconductor and the on logo are trademarks of semiconductor components industries, llc (scillc). on semiconductor reserves the right to make changes without further notice to any products herein. for additional infor- mation and the latest available information, please contact your local on semiconductor representative. ?semiconductor components industries, llc, 2000 archive device not recommended for new design 5 lead to-220 (t) straight 2.87 (.113) 2.62 (.103) 6.93(.273) 6.68(.263) 9.78 (.385) 10.54 (.415) 1.02(.040) 0.63(.025) 1.83(.072) 1.57(.062) 0.56 (.022) 0.36 (.014) 2.92 (.115) 2.29 (.090) 1.40 (.055) 1.14 (.045) 4.83 (.190) 4.06 (.160) 6.55 (.258) 5.94 (.234) 14.22 (.560) 13.72 (.540) 1.02 (.040) 0.76 (.030) 3.71 (.146) 3.96 (.156) 14.99 (.590) 14.22 (.560)
notes
8 notes
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