Low-cost electrostatic discharge (ESD) protection device for high-voltage open-drain pad

摘要

A low-cost ESD protection device for high-voltage open-drain pad is disclosed, which has a first high-voltage (HV) NMOSFET coupled to a high-voltage (HV) open drain pad, a ground pad, a HV block unit and an ESD clamp unit and a low-voltage (LV) bias unit coupled to the first HV NMOSFET, a low-voltage (LV) trigger, the ESD clamp unit and the ground pad. The LV trigger is coupled to the HV block unit. The HV block unit blocks a high voltage from the HV open drain pad diode during normal operation and generates a trigger signal to the LV trigger when an ESD event is applied to the HV open drain pad. Then, the LV trigger turns on the ESD clamp unit to discharge an ESD current and switches the LV bias unit to turn off the first HV NMOSFET.

主权项

1. A low-cost electrostatic discharge (ESD) protection device for high-voltage open-drain pad, comprising:
a first high-voltage N-channel metal oxide semiconductor field effect transistor (HV NMOSFET) coupled to a high-voltage (HV) open drain pad and a low-voltage (LV) ground pad; a diode coupled to said HV open drain pad, a high-voltage (HV) block unit and an electrostatic discharge (ESD) clamp unit, wherein said diode is used for multi-channel open drain application to share same said ESD clamp unit, and wherein said diode is removed in single channel application; and a low-voltage (LV) bias unit coupled to a gate of said first HV NMOSFET, a low-voltage (LV) trigger, and said LV ground pad, wherein said LV bias unit is disabled during normal operation, and said HV block unit is coupled to said ESD clamp unit and said LV trigger, blocks a high voltage from said diode during said normal operation and generates a trigger signal to said LV trigger when an ESD event is applied to said HV open drain pad, and said LV trigger is coupled to said HV block unit, said ESD clamp unit and said LV ground pad, wherein when said ESD event is applied to said HV open drain pad, said LV trigger turns on said ESD clamp unit to discharge an ESD current and switches said LV bias unit to turn off said first HV NMOSFET, wherein said LV trigger unit is disabled during said normal operation, and said ESD clamp unit is coupled to said HV block unit and said LV ground pad, wherein said ESD clamp unit is disabled during said normal operation.