An externally adjustable overcurrent protection circuit that does not require any additional chip pins was proposed in this paper. The effect of process deviations on the overcurrent threshold was reduced by sampling the rectifier MOSFET on-resistance and superimposing positive and negative voltages. The digital-to-analog converter (DAC) was used to control the driver stage so that the LGATE pin of the chip was multiplexed, and the internal constant current source flowed through different external resistors from this port to set different overcurrent thresholds, and this port was used to drive the gate of the rectifier MOSFET after the overcurrent point was set. This design avoided the need for additional overcurrent setting pins, reducing costs. The converter was fabricated in 0.35 μm BCD process and had a chip area of about 1.65 mm 2 , of which the overcurrent protection circuits accounts for about 3%. Simulation results show that after the chip is powered on, the LGATE terminal first complete the overcurrent point setting and then is used to drive the rectifier. The overcurrent threshold ranges from 5A to 35A with a maximum deviation of 5.4% by adjusting four different sets of external resistors at an input voltage of 6~13V.