Abstract: The relation between the maximum temperature and the switching condition of an LDMOST under different frequencies is studied.The results show that the maximum temperature in the device depends on the thermal capacitance,the power dissipation,the duty cycle,and the duration of continuous operation under a high switching frequency.Under a low switching frequency,the maximum temperature depends not only on those four parameters,but also on the thermal resistance and the period of the cycle.The results given here can be used as a reference for designing the thermal safe operation conditions of power devices.

Key words: thermal safety, the maximum temperature, switching frequencies