3843 PWM

The UC3843 control IC 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. Differences between members of this family are the under-voltage lockout thresholds and maximum duty cycle ranges. The UC3843 can operate to duty cycles approaching 100%. 

Features

• Optimized for OFF-LINE and DC to DC converters

• Low Start-Up Current (<1mA)

• Automatic Feed Forward Compensation

• Pulse-by-pulse current limiting

• Enhanced load response characteristics

• Under-voltage lockout with hysteresis

• Double pulse suppression

• High current totem pole output

• Internally trimmed bandgap reference