UC2842BN Datasheet | STMicroelectronics

DESCRIPTION Differences between members of this family are the under-voltagelockout thresholds and maximum duty The UC384x B family ofcontrol ICs providesthe nec- cycle 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 wit.Dhata Sheet4Us.cuomitedoff-lineapplications Thecorrespondingthresh- a minimal external parts count. Internally imple- oldsforthe UC3843Band UC3845Bare8.5 V and7.9 mented circuits include a trimmed oscillator for pre- V. The UC3842B and UC3843B can operate to duty cise DUTY CYCLE CONTROL under voltage lock- cycles approaching 100%. A range of the zero to < outfeaturingstart-up current less than0.5m A,a pre- 50 % 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) 7 Vi 5 GROUND 4 RT/CT 2 VFB 1 P CURRENT 3 SENSE 34V UVLO S/R 5V REF 2.50V OSC VREF GOOD LOGIC INTERNAL BIAS 8 VREF 5V 50m A 6 OUTPUT ERROR AMP. + 2R R 1V CURRENT SENSE PARATOR PWM LATCH UC3842B D95IN331 March 1999 1/15 UC2842B/3B/4B/5B - UC3842B/3B/4B/5B ABSOLUTE MAXIMUM RATINGS Sy mb o l P ar ame te r Vi Supply Voltage (low impedance source) Vi Supply Voltage (Ii < 30m...