Patent ID: 7715165
Filing Date: 2010-05-11
Classification: H04L

Abstract:
1. A powered device comprising: a first supply terminal and a second supply terminal; at least one input pin coupled to the first supply terminal; an external capacitor having a first terminal coupled to the at least one pin of the first supply terminal and having a second terminal; a switch coupled to the second supply terminal and coupled to the second terminal of the external capacitor to selectively couple the external capacitor between the first and second supply terminals, wherein the switch comprises a field effect transistor including a source terminal coupled to the second terminal of the external capacitor, a gate terminal, and a drain terminal coupled to the second supply terminal; and power surge detection logic coupled to the gate terminal of the switch; wherein the external capacitor is charged in response to a detected power surge that exceeds a threshold voltage; wherein current is fed back from the drain terminal to the gate terminal via the power surge detection logic to change a gate voltage at the gate of the field effect transistor.