unisonic technologies co., ltd uc3842g linear integrated circuit www.unisonic.com.tw 1 of 8 copyright ? 2012 unisonic technologies co., ltd qw-r103-036.c high performance current mode controller description the utc uc3842g of high performance current mode controller is specifically designed for off-line and dc-to-dc converter applications offering the designer a cost effective solution with minimal external components. this integrated circuit features approximately 40 a start up current, a precision reference trimmed the error amplifier input. also included are protective features consis ting of input and reference undervoltage lockouts each with hysteresis, cycle-by-cycle current limiting, and so on. features * low startup and operating current * user defined switching frequency(norm is 52khz) * power-saving mode for low power * under voltage lockout with hysteresis * over voltage protection * latching pwm for cycle-by-cycle current limiting * internally trimmed reference with undervoltage lockout ? ordering information ordering number package packing lead free halogen free uc3842gl-s08-r uc3842gp- s08-r sop-8 tape reel uc3842gl-s08-t UC3842GP-S08-T sop-8 tube uc3842gl-d08-t uc3842g p-d08-t dip-8 tube
uc3842g linear integrated circuit unisonic technologies co., ltd 2 of 8 www.unisonic.com.tw qw-r103-036.c ? pin configuration gnd out v cc v ref ct cs fb comp 1 2 3 4 8 7 6 5 pin description pin no. pin name i/o function 1 comp o this pin is error amplifier output 2 fb i the error amplifier inverting input 3 cs i current sense input 4 ct i the capacitor controlling switch frequency 5 gnd ground 6 out o output to the gate of external power mos 7 v cc supply voltage 8 v ref o inter 5v reference voltage output
uc3842g linear integrated circuit unisonic technologies co., ltd 3 of 8 www.unisonic.com.tw qw-r103-036.c block diagram
uc3842g linear integrated circuit unisonic technologies co., ltd 4 of 8 www.unisonic.com.tw qw-r103-036.c ? absolute maximum ratings (t a 25c) parameter symbol ratings unit supply voltage (low impedance source) v cc 30 v supply voltage (i cc <30ma) v cc self limiting v output current (peak) i o ( peak ) 1 a output energy (capacity load) 5 j junction temperature t j +150 c operating temperature t opr -40 ~ +125 c storage temperature t stg -65 ~ +150 c note: absolute maximum ratings are those values be yond which the device could be permanently damaged. absolute maximum ratings are stress ratings only and functional device oper ation is not implied. ? electrical characteristics (0c t a 70c, v cc =15v, c t =3.3nf , unless otherwise specified) parameter symbol test condition min typ max unit standby section reduce frequency point of standby mode v comp right load 2.2 v reference section reference output voltage v ref i out =1.0ma 4.95 5.0 5.05 v line regulation v ref 12v v cc 25v 3 20 mv load regulation v ref i out =1.0ma to 20ma 8 25 mv output short circuit current i sc -30 -65 -180 ma oscillator section frequency f osc normal 49 52 55 khz frequency change f osc / v 12v v cc 25v 0.2 1.0 oscillator voltage v osc ( p-p ) 1.6 v v oscl 1.2 v v osch 2.8 v error amplifier section input voltage v i ( ea ) v comp =2.5v 2.42 2.50 2.58 v input bias current i i ( bias ) v fb =5v -0.3 -2 a avol 2v v out 4v 60 90 db unity gain bandwidth t j =25c(note1) 0.7 1 mhz psrr 12v v cc 25v 60 70 db output sink current i sink v fb =2.7v, v comp =1.1v 2 4 ma output source current i source v fb =2.3v, v comp =5v -0.5 1 ma v out high v oh v fb =2.3v, r l =15k to gnd 5.0 5.6 v v out low v ol v fb =2.7v, r l =15k to v ref 0.8 1.1 v current sense section gain g v (note2,3) 2.85 3 3.15 v/v maximum input signal v i ( max ) v comp =5v(note2) 0.9 1 1.1 v psrr 12v v cc 25v 70 db input bias current i bias -2 -10 a delay to output 150 300 ns
uc3842g linear integrated circuit unisonic technologies co., ltd 5 of 8 www.unisonic.com.tw qw-r103-036.c ? electrical characteristics (cont.) parameter symbol test condition min typ max unit output section output voltage with uvlo active v ol(uvlo) v cc =6v,i sink =0.1ma; v cc =7.5v,i sink =1ma 0.8 1.1 v output voltage v ol i sink =20ma 0.1 0.4 v i sink =200ma 1.6 2.2 v v oh i source =20ma 13 14.5 v i source =200ma 12 14.6 v output voltage rise and fall time t r c l =1.0nf (note 1) 100 150 ns t f c l =1.0nf (note 1) 100 150 under voltage lockout section startup threshold v th ( star-up ) 13.5 15 16.5 v min operating voltage v opr ( min ) after turn-on 8.5 10 11.5 v pwm section max duty cycle d max 92 94 % minimum duty cycle d min 0 % total device power supply zener voltage v z i cc =25ma 30 39 v power operating supply current i cc note 2 7 10 ma startup current i start-up v cc =14v,uvlo active 15 40 a note: 1. 2. 3. these parameters, although guaranteed, are not 100% tested in production. parameters measured at trip point of latch with v fb =0. gain defined as: a= v comp / v cs ; 0 v cs 0.8v
uc3842g linear integrated circuit unisonic technologies co., ltd 6 of 8 www.unisonic.com.tw qw-r103-036.c ? open-loop test circuit high peak current associated with capacity loads necessitate careful grounding techniques. timing and bypass capacitors should be connected close to pin5 in single point gnd. ? under-voltage lockout during under-voltage lockout, the output driver is biased to a high impedance state. pin 6 should be shunt to gnd with a bleeder resistor to prevent activing the power switch with output leakage currents. ? error amplifier configuration error amplifier can source or sink up to 0.5ma
uc3842g linear integrated circuit unisonic technologies co., ltd 7 of 8 www.unisonic.com.tw qw-r103-036.c ? current sense circuit 5 3 1 2r r1v c rs r is error amplifier current sense comparator peak current (i s ) determined by the formula: i smax =1v/rs. a small rc filter be required to suppress switch transients ? oscillator and standby mode we can judge the state of output lo ad through the voltage of pin 1. in order to reduce the standby power, it will reduce the osc frequency at right load. when v comp 2.2v, the osc frequency begins to reduce. the normal frequency is 52khz, the minimum frequency is 22khz. 2.2v 1.2v standby mode minimum frequency :14khz normal frequency: 52khz normal frequency: 52khz v comp increase osc triangle wave
uc3842g linear integrated circuit unisonic technologies co., ltd 8 of 8 www.unisonic.com.tw qw-r103-036.c ? shutdown technique 8 3 330 ? 500 ? 1k ? 1 shutdown to current sense resistor shutdown shutdown utc uc3842g can be accomplished by two methods; either raise pin 3 above 1v or pull pin 1 below a voltage two diode drops above ground. utc assumes no responsibility for equipment failures that result from using products at values that exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or other parameters) listed in products specifications of any and all utc products described or contained herein. utc products are not designed for use in life support appliances, devices or systems where malfunction of these products can be reasonably expected to result in personal injury. reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. the information presented in this document does not form part of any quotation or contract, is believed to be accurate and reliable and may be changed without notice.
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