Power-supply feedthrough protection circuit for 5-volt failsafe CMOS drivers

摘要

A power supply feedthrough protection circuit which solves the problem of voltage feedthrough from a bus cable charging a chip power-supply beyond acceptable transistor limits. The circuit continuously senses the chip power-supply, compares the supply to an acceptable threshold, and provides a low-impedance current path as soon as the power-supply exceeds the threshold. The circuit allows a driver to draw current from the cable, in a controlled manner, and provides that the power supply is therefore never allowed to exceed the maximum allowable limit for transistors.