The HY3842D-N/3843D-N/3844D-N/3845D-N, are fixed frequency current mode PWM controller. Theyare speciallydesigned for OFF−Line and DC to DC converter applications with a minimal externalcomponents. Internallyimplemented circuits include a trimmed oscillator for precise duty cycle control, a temperature compensated reference, high gain error amplifier, current sensing comparator, and a high current totem pole output ideally  suited for driving a power MOSFET. Protection circuitry includes built under  voltage lockout and current limiting.