UC2842B

® UC2842B/3B/4B/5B UC3842B/3B/4B/5B HIGH PERFORMANCE CURRENT MODE PWM CONTROLLER comparatorwhich alsoprovidescurrent limit control, and a totem pole output stage designed to source or sink high peakcurrent. The outputstage, suitable for driving N-Channel MOSFETs, is low in the offstate. Differences between members of this family are the DESCRIPTION under-voltagelockout thresholds and maximum duty TheUC384xB family ofcontrolICs providesthe neccycle ranges. The UC3842B and UC3844B have essary features to implement off-line or DC to DC UVLO thresholds of 16V (on) and 10V (off), ideally fixed frequency current mode control schemes www.DataSheet4U.com with suitedoff-lineapplicationsThecorrespondingthresha minimal external parts count. Internally impleoldsforthe UC3843BandUC3845Bare8.5 V and7.9 mented circuits include a trimmed oscillator for preV. The UC3842B and UC3843B can operate to duty cycles approaching 100%. A range of the zero to < cise DUTY CYCLE CONTROL under voltage lockoutfeaturingstart-up current less than0.5mA,a pre50 % is obtained by the UC3844B and UC3845B by cision reference trimmed for accuracy at the error the addition of an internal toggle flip flopwhich blanks amp input, logicto insure latched operation,a PWM the output off every otherclock cycle. BLOCK DIAGRAM (toggle flip flop used only in UC3844B and UC3845B) Vi 7 34V GROUND 5 UVLO S/R 5V REF INTERNAL BIAS VREF GOOD LOGIC RT/CT 4 OSC ERROR AMP. 2R R 1V T . . . . . . . . . TRIMMED OSCILLATOR FOR PRECISE...