A monolithic current limiting power MOSFET

Abstract

A new monolithic current limiting power MOSFET is proposed. The MOSFET consists of a main power cell, a sensing cell and a lateral npn bipolar transistor. The proposed MOSFET may be fabricated by a conventional DMOS process without an additional mask step. Overcurrent state is sensed by the pinched resistor of the npn transistor so that any additional sensing resistor is not required. Sensing voltage at the pinched base resistor is 0.7 V. The limiting current level is adjusted easily by an external resistor. Simulation results show that the on-resistance of the power MOSFET is not deteriorated by the sensing and protection circuit. Overcurrent protection is achieved successfully with the protection area less than 0.2% of the whole die area.<>