Circuits and methods for enabling redundancy in an electronic system employing cold-sparing

Abstract

CMOS output stages, electrostatic discharge (ESD) protection circuits and input bus-keeper functions are provided that block dc and ac leakage paths within inactive powered-down integrated circuits used in redundant high-reliability system configurations employing cold-sparing to provide backup circuitry. These circuits and methods avoid both undesirable power consumption in a cold-spared backup unit and loading of connected active units when powered down, without compromising performance or functionality of the backup unit when in its active powered state. Inputs and outputs using an analog majority voting principle to implement in-circuit redundancy for on-chip fault tolerance are also provided, incorporating the low-leakage principles of the invention for low power dissipation when powered down. Such on-chip redundancy can harden an IC against various faults, such as single-event effects in high-radiation environments, while maintaining the other advantages in a cold-sparing system.