A reverse-voltage protection circuit for MOSFET power switches

When MOSFET is used as a power switch, if is essential to prevent reverse c urrent flow through the parasitic body diodes under reverse voltage conditi on. A new built-in reverse voltage protection circuit for MOSFETs has been developed. In this design, an area-efficient circuit is used to automatical ly select the proper well bias voltage to prevent reverse current under the reverse-voltage condition. This built-in reverse protection circuit has be en successfully implemented in a high-side power switch application using a 0.6-mum CMOS process. The die area of the protection circuit is only 2.63 % of that of a MOSFET. The latch-up immunity is greater than +12 V and -10 V in voltage triggering mode, and greater than +/-500 mA in current trigger ing mode, The protection circuit is not in series with the MOSFET switch, s o that the full output swing and high power efficiency are achieved.