UTC3842

UTC3842 LINEAR INTEGRATED CIRCUIT CURRENT MODE PWM CONTROL CIRCUITS DESCRIPTION The UTC3842 provides the 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 under-voltage lockout featuring start up current less than 1mA,a precision reference trimmed for accuracy at the error amp input, logic to insure latched operation, a PWM comparator which also provides current limit control, and a totem pole output stage designed to source or sink high peak current. The output stage, suitable for driving N channel MOSFETs, is low in the off state. DIP-8 SOP-8 FEATURES *Optimized for off-line and DC to DC converts *Low start up current(<1mA) *Automatic feed forward compensation *Pulse-by-Pulse current limiting *Enhanced load response characteristics *Under-voltage lockout with hysteresis BLOCK DIAGRAM *Double pulse Suppression *High current totem pole output *Internally trimmed band-gap reference *500kHz operation *Low Ro error amp Vref 8 Internal Bias VFB 2 COMP 1 CURRENT SENSE 3 RT/CT 4 1/2Vref ERROR AMPLIFIER 5V REF S/R Vref Good Logic 1/3Vref U.V.L.O CURRENT SENSE COMPAREATOR 1V R PWM LATCH S OSCILLATOR 7 Vcc 5 GND 7 Vcc 6 OUTPUT 5 GND YOUWANG ELECTRONICS CO.LTD 1 2005.06.09 V1.1 UTC3842 LINEAR INTEGRATED CIRCUIT ABSOLUTE MAXIMUM RATINGS(Ta=25°C) Characteristic Symbol Supply Voltage(Low Impedance Source) VCC Supply Voltage(Icc<30mA) Vcc ...