Abstract: In this paper, an overcurrent protection circuit with high-precision programmable threshold is proposed based on the current-mode synchronous step-down DC-DC converter. A full-cycle sampling circuit based on SENSEFET current sampling is designed, which solves the disadvantage that only half a cycle can be sampled. The current threshold is programmed and the circuit is trimmed by the external resistor, which increases the current protection range and reduces the current threshold, which is affected by temperature and other factors. A comparator consisting of a three-stage op-amp is used to improve the comparison speed of the circuit. The circuit is designed using a $ 0.18 \mu m $ BCD process, and the simulation results show that the circuit can perform fast (10 ns) and accurate (96% accuracy) current protection, and can be applied to many types of DC-DC chips.
Keywords: DC-DC converter; current sampling; programmable threshold; high precision; high speed (constant on-time, COT)