Western Digital Corporation

Kwok Fai Lee

Kenneth W Ouyang

Alan Y Lee

Melvin L Marmet

Ramon Co

An electrostatic discharge protection circuit employing an extended resistive structure having bimodal resistance characteristics in series with an input/output buffer circuit and an input/output electrical contact pad on an integrated circuit. The extended resistive structure is integrally formed with the device or devices in the buffer circuit most susceptible to damage due to ESD breakdown effects In a first resistance mode during normal circuit operations, the resistor has a low resistance value and introduces virtually no additional load to the input/output buffer circuitry. In a second mode of operation during ESD discharge, the resistor has a second significantly higher resistance which reduces current values during the ESD event thereby protecting the buffer circuit. Thick oxide snap-back device is also employed to provide a parallel ESD discharge path with low power dissipation.

Electro-static discharge protection circuit with bimodal resistance

An electrostatic discharge (ESD) protection circuit for protecting internal devices of an integrated circuit is coupled between the power rails of the integrated circuit. First and second current shunt paths between the power rails are maintained non-conductive during normal circuit operation and are triggered to a conductive mode in response to an ESD event on the power rails. A triggering circuit may employ a logic gate, such as an inverter with its input coupled to the positive power rail, which maintains a low level output during normal operation and provides a high output in response to an ESD event on the power rail.

Power rail ESD protection circuit

An integrated circuit electrostatic discharge (ESD) protection circuit employs a capacitor and a zener diode to trigger a thick oxide ESD shunt field effect transistor (FET). When an ESD induced voltage at an input or output node reaches the turn-on voltage determined by the zener diode breakdown voltage, the shunting transistor is turned on by current capacitively coupled to the base of the parasitic bipolar transistor inherently formed in the thick oxide FET. The parasitic bipolar transistor is turned on in its saturated mode, substantially shorting the node to ground. At the end of the ESD event when the ESD induced current is no longer sufficient to keep the shunting transistor in its saturated mode, the shunting transistor turns off and the ESD protection circuit returns to its off mode, monitoring the input or output node for the occurrence of another ESD event.

Growing community of inventors

Irvine, CA, United States of America

Kwok Fai Lee