DESCRIPTION
under-voltagelockout thresholds and maximum duty TheUC384xB family ofcontrolICs providesthe neccycle ranges. Internally impleoldsforthe UC3843BandUC3845Bare8.5 V and7.9 mented circuits include a trimmed oscillator for preV. 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 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 TRI...
STMicroelectronics
