The UC3842/UC3843/UC3844/UC3845 are fixed-frequency current-mode PWM controllers. They are specially designed for off-line and DC-to-DC converter applications with minimum external components. These integrated circuits feature a trimmed oscillator for precise duty cycle control, a temperature-compensated reference, a high-gain error amplifier, a current-sensing comparator, and a high-current totem pole output for driving a power MOSFET. The UC3842 and UC3844 have UVLO thresholds of 16 V (on) and 10 10V (off). The UC3843 and UC3845 are 8.5V (on) and 7.9V (off). The UC3842 and UC3843 can operate within a 100% duty cycle. The UC3844 and UC3845 can operate with a 50% duty cycle.

Features:

• Low Start up Current
• Maximum Duty Clamp
• UVLO With Hysteresis
• Operating Frequency up to 500KHz

Datasheet: https://www.mouser.com/datasheet/2/149/uc3843-309322.pdf