Max-supply selector using a voltage comparator

Higher supply line selector is an integral part of a multi-supply power management integrated circuit (IC). This document talks about a CMOS implementation of higher-supply-line selector circuit. The selector circuit uses a proposed supply line comparator. To avoid unwanted hazard for equal potential at the supply lines, the comparator has hysteresis in its switching characteristic. Operating principle of the proposed comparator discussed in detail. The higher-supply-line selector circuit is used in a 3.0V/5.0V power supervisor chip which is implemented in a 0.5mum CMOS process. The silicon-measured data is consistent with predicted simulation results. The proposed circuit idea can be extended for more than two supplies environment. Additionally, similar implementation can be adopted using bi-polar or in Bi-CMOS circuits