Patent ID: 6965504
Filing Date: 2005-11-15
Classification: H01L

Abstract:
1. An ESD protection apparatus for a high-voltage input pad, comprising: a modulator connected to the input pad for adjusting a triggering voltage and a holding voltage of the protection apparatus; a first guard ring of a first conductivity type surrounding the modulator; a second guard ring of a second conductivity type opposite to the first conductivity type surrounding the first guard ring; a snapback device connected to the modulator; a third guard ring of the first conductivity type surrounding the snapback device; a first guard ring control circuit connected the first and third guard rings for controlling the first and third guard rings connected to a first voltage under a normal operation and floated under an ESD event; and a second guard ring control circuit connected the second guard ring for controlling the second guard ring connected to a second voltage under the normal operation and floated under the ESD event.