UC3843B

www.DataSheet4U.com ® UC2842B/3B/4B/5B UC3842B/3B/4B/5B HIGH PERFORMANCE CURRENT MODE PWM CONTROLLER . . . . . . . . . TRIMMED OSCILLATOR FOR PRECISE FREQUENCY CONTROL OSCILLATOR FREQUENCY GUARANTEED AT 250kHz CURRENT MODE OPERATION TO 500kHz AUTOMATIC FEED FORWARD COMPENSATION LATCHING PWM FOR CYCLE-BY-CYCLE CURRENT LIMITING INTERNALLY TRIMMED REFERENCE WITH UNDERVOLTAGE LOCKOUT HIGH CURRENT TOTEM POLE OUTPUT UNDERVOLTAGE LOCKOUT WITH HYSTERESIS LOW START-UP AND OPERATING CURRENT Minidip SO8 DESCRIPTION TheUC384xB family ofcontrolICs providesthe necessary features to implement off-line or DC to DC fixed frequency current mode control schemes with a minimal external parts count. Internally implemented circuits include a trimmed oscillator for precise DUTY CYCLE CONTROL under voltage lockoutfeaturingstart-up current less than0.5mA,a precision reference trimmed for accuracy at the error amp input, logicto insure latched operation,a PWM 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 under-voltagelockout thresholds and maximum duty cycle ranges. The UC3842B and UC3844B have UVLO thresholds of 16V (on) and 10V (off), ideally suitedoff-lineapplicationsThecorrespondingthresholdsforthe UC3843BandUC3845Bare8.5 V and7.9 V. The UC3842B and UC3843B can operate to duty cyc...