ELECTROSTATIC DISCHARGE PROTECTION CIRCUIT AND METHOD OF OPERATION

摘要

An ESD protection circuit ( 201 ) is for use with a high-voltage tolerant I/O circuit in an IC. This is accomplished by providing a small ESD diode ( 217 ) from the I/O pad to a relatively small boosted voltage bus (BOOST BUS). The BOOST BUS is used to power a trigger circuit ( 203 ). This path has very little current flow during an ESD event due to minimal current dissipation in the trigger circuit. There is a diode drop but only very little IR voltage drop from the I/O pad to the trigger circuit ( 203 ). The trigger circuit ( 203 ) controls relatively large cascoded clamp NMOSFETs ( 207, 209 ). The net result is that a gate-to-source voltage (VGS) of both of the clamp NMOSFETs is increased thus increasing the conductivity of the cascoded clamp NMOSFETs ( 207, 209 ). This reduces the on-resistance of each of the NMOSFETS ( 207, 209 ), thereby improving the ESD performance, and reducing the layout area required to implement robust ESD protection circuits.