Patent ID: 7480126
Filing Date: 2009-01-20
Classification: H02H,H03K

Abstract:
1. A protection circuit comprising: an output terminal; an input terminal operable to receive an external voltage; a first transistor including a gate terminal, a drain terminal, and a source terminal, wherein the drain terminal of the first transistor is coupled to the input terminal of the protection circuit; a second transistor including a gate terminal, a drain terminal, and a source terminal, wherein the drain terminal of the second transistor is coupled to the output terminal of the protection circuit, the gate terminal of the second transistor is coupled to the gate terminal of the first transistor, and the source terminal of the second transistor is coupled to the source terminal of the first transistor; a first resistor coupled between a junction of the source terminals of the first and second transistors and a junction of the gate terminals of the first and second transistors; a current source coupled to the junction of the gate terminals of the first and second transistors and to the first resistor to limit a gate-to-source voltage of the first and second transistors to a predetermined voltage value that is less than a maximum allowed voltage value; and a voltage monitoring circuit coupled to the current source, wherein the voltage monitoring circuit includes: