UC3843AD – UNITRODE

The UC3843AD is a fixed-frequency current-mode PWM controller integrated circuit, manufactured in a 14-pin SOIC package. This device is optimized for off-line and DC-to-DC converter applications, providing the necessary features to implement single-ended or flyback topologies. It incorporates an internal oscillator, trimmed for precise duty cycle control, operating at a typical frequency of 500kHz. The UC3843AD features undervoltage lockout (UVLO) circuitry with hysteresis for reliable startup, a current-sense comparator with a typical propagation delay of 100ns, and a high-current totem-pole output stage capable of directly driving a power MOSFET. Furthermore, it includes a precision reference voltage of 5V with ±1% accuracy and a soft-start function to minimize stress during power-up. The device’s current-mode control architecture provides inherent pulse-by-pulse current limiting and improved dynamic response.