Field oxide transistor based feedback circuit for electrical overstress protection

摘要

A circuit for protecting an interface cable driver and the circuitry attached to the driver from electrical overstress damage, such as that which may arise from an electrostatic discharge. The protection circuit includes a sensing element, typically a field oxide transistor, which is used to sense when an EOS transient raises the input/output voltage above the normal operating range. The sensing element is configured to change logic state when the transient reaches a predetermined threshold level. The change in state is used as a feedback path to turn on the interface driver transistor connected to ground and turn off the interface driver transistor connected to the power supply. The interface driver transistor connected to ground then acts to shunt away the transient, preventing damage to the driver and internal circuitry.