Patent ID: 7072161

Claim:
A two-stage electrostatic discharge (ESD) protection circuit, comprising: a primary ESD protection circuit comprising: a first primary discharging component, having a first control end; and a first primary ESD detection circuit, comprising: a first capacitor and a first resistor formed in series, and coupled between the first control end and a input/output pad of an IC; and a second resistor, coupled between the first control end and a first pad of the IC; a buffering resistor coupled between the input/output pad of the IC and an internal circuit of the IC; and a secondary ESD protection circuit comprising: a second primary discharging component, having a second control end; and a second ESD detection circuit, comprising: a second capacitor and a third resistor formed in series, and coupled between the second control end and the internal circuit of the IC; and a fourth resistor, coupled between the secoud control end and the first pad; wherein the first and the second primary discharging components are closed during normal power operations, and triggered by the ESD detection circuit during an ESD event.