Patent ID: 7106562

Claim:
A protection circuit section provided in a semiconductor circuit system, which has first, second, and third external terminals electrically separated from each other, the first external terminal being configured to receive a first power supply voltage in a normal operation, the protection circuit section comprising: a rectifier configured to allow a surge current to pass therethrough, the rectifier including a PNP transistor and an NPN transistor combined to equivalently form a thyristor, and the rectifier having a first current passage connected between a specific terminal connected to a protection target and the third external terminal; and a first PMOS transistor configured to trigger the rectifier, based on a surge voltage inputted into the second external terminal, the first PMOS transistor having a second current passage connected between the second external terminal and a base of the NPN transistor, the first PMOS transistor having a source and a channel region connected to each other, and the first PMOS transistor having a gate connected to the first external terminal, wherein the semiconductor circuit system further has a fourth external terminal electrically separated from the first and third external terminals, and a fifth external terminal electrically separated from the first, second, third, and fourth external terminals, the fifth external terminal being configured to receive a second power supply voltage in the normal operation, and wherein the protection circuit section further comprises a second PMOS transistor configured to trigger the rectifier, based on a second surge voltage inputted into the fourth external terminal, the second PMOS transistor having a third current passage connected between the fourth external terminal and the base of the NPN transistor, the second PMOS transistor having a source and a channel region connected to each other, and the second PMOS transistor having a gate connected to the fifth external terminal, and wherein the semiconductor circuit system further has a sixth external terminal electrically separated from the first, third, and fifth external terminals, and the specific terminal is the sixth external terminal.