High precision adjustable current limit protection circuit for power protection switches

Abstract

In order to improve the flexibility of the current protection circuit operation, a current protection circuit that can change the current limit value by adjusting the resistance value of the external resistor is designed. The load current is sampled using a sense-FET sensing circuit designed with an improved common-source common-gate current mirror, which reduces losses while ensuring the accuracy of the current limit value. The current is processed through two different branches to improve the efficiency of fault handling. The design is implemented using a 0.18 μm BCD process. Simulation results show that at a supply voltage of 12 V, current limit range of 1 A~5 A, the accuracy is less than 0.96% affected by temperature, the fast shutdown time is about 70 ns, and the completion of the protection time is about 1 μs.