A Double-Threshold Over-Temperature Protection Circuit for Smart Power ICs

Smart power ICs often work in a high temperature environment, the junction temperature of the power MOSFET will be affected by the ambient temperature. Therefore, this work adds an ambient temperature sensor to detect the ambient temperature of the chip. When the ambient temperature is normal, the over-temperature threshold of the junction temperature sensor is adjusted to a high threshold, which can ensure the normal operation under high voltage and high current. When the ambient temperature is too high, the over-temperature shutdown threshold of the junction temperature sensor is adjusted to a low threshold, which prevent the thermal load on the chip caused by the untimely response of the junction temperature sensor. In addition, the temperature sensor designed in this paper uses the reverse current of the transistor to detect the temperature, which has the advantages of high sensitivity, simple circuit structure and low power consumption. The circuit is designed based on 60V0.35μm BCD process. The simulation results show that the over-temperature threshold of the ambient temperature sensor is $135^{\circ}\mathrm{C}$, and the hysteresis temperature is $5^{\circ}\mathrm{C}$. The junction temperature sensor has a high over-temperature threshold of $180^{\circ}\mathrm{C}$, a low over-temperature threshold of 1$50^{\circ}\mathrm{C}$, and all hysteresis temperature of 1$0^{\circ}\mathrm{C}$.