Patent ID: 8164112

Claim:
An electrostatic discharge (ESD) protection circuit, comprising: a silicon controlled rectifier (SCR), which comprises a first connection terminal, a second connection terminal, and a third connection terminal, wherein the first connection terminal and the second connection terminal are respectively and directly connected to an I/O pad and a ground voltage, so as to discharge the electrostatic charges; an anti-latch-up circuit, which comprises a fourth connection terminal directly connected to a voltage source, a fifth connection terminal directly coupled to the ground voltage, and a sixth connection terminal directly connected to the third connection terminal of the SCR, wherein the anti-latch-up circuit consists of a capacitor and a resistor, a first end of the resistor is directly connected to the fourth connection terminal, a second end of the resistor is directly connected to the sixth connection terminal, a first contact end of the capacitor is directly connected to the sixth connection terminal and a second contact end of the capacitor is directly connected to the fifth connection terminal; and a first diode, having an anode directly connected to the I/O pad and a cathode directly connected to the fourth connection terminal, wherein when an over positive voltage does not occur on the I/O pad, the first diode is not conducted, and the anti-latch-up circuit substantially generates an anti-latch-up signal to the third connection terminal of the SCR according to the voltage source so as to prevent latching up of the SCR during normal operation, and when the over positive voltage occurs on the I/O pad, the first diode is conducted, and the anti-latch-up circuit does not substantially generate the anti-latch-up signal in response to the conduction of the first diode.