A CMOS power backup switching circuit and method for operating a CMOS power backup switching circuit

摘要

A Complementary Metal Oxide Semiconductor (CMOS) power switching circuit and a method for operating a CMOS power switching circuit are described. A CMOS power switching circuit includes a voltage selection circuit configured to output the highest output voltage between an output voltage of a primary power supply and an output voltage of a backup power supply and a control circuit configured to connect a load circuit to either the primary power supply or the backup power supply by comparing the output voltage of the primary power supply with a power supply switchover level that is set as a function of the highest output voltage. The backup power supply serves as a voltage reference to set the power supply switchover level only when the output voltage of the primary power supply is lower than the output voltage of the backup power supply.