Patent ID: 8817437

Claim:
A high voltage open-drain electrostatic discharge (ESD) protection device, comprising: a first high-voltage n-channel metal oxide semiconductor field effect transistor (HV NMOSFET) coupled to a high-voltage pad and a low-voltage terminal and receiving a high voltage on said high-voltage pad to operate in a normal operation; a high-voltage ESD unit coupled to said high-voltage pad and said first HV NMOSFET, blocking said high voltage, and receiving a positive ESD voltage or a negative ESD voltage on said high-voltage pad to bypass a first ESD current or a second ESD current respectively when an ESD event is applied to said high-voltage pad; and a first power clamp unit coupled to said high-voltage ESD unit and said low-voltage terminal, and receiving said positive ESD voltage via said high-voltage ESD unit to bypass said first ESD current.