Overvoltage protection circuit

摘要

Universal Serial Bus (USB) protection circuits are provided. A circuit includes a plurality of first transistors connected in series between a pad and ground. The circuit also includes a plurality of second transistors connected in series between the pad and a supply voltage. The circuit further includes a control circuit that applies respective bias voltages to each one of the plurality of first transistors and to each one of the plurality of second transistors. The bias voltages are configured to: turn off the plurality of first transistors and turn off the plurality of second transistors when a pad voltage of the pad is within a nominal voltage range; sequentially turn on the plurality of first transistors when the pad voltage increases above the nominal voltage range; and sequentially turn on the plurality of second transistors when the pad voltage decreases below the nominal voltage range.

主权项

1. A circuit, comprising:
a plurality of first transistors connected in series between a pad and ground; a plurality of second transistors connected in series between the pad and a supply voltage; at least one of: a first resistance element connected in series with a drain of one of the first transistors and ground; and a second resistance element connected in series with a drain of one of the second transistors and the supply voltage; and a control circuit that applies respective bias voltages to each one of the plurality of first transistors and to each one of the plurality of second transistors, the control circuit comprising a voltage divider, wherein the bias voltages are configured to: turn off the plurality of first transistors and turn off the plurality of second transistors when a pad voltage of the pad is within a nominal voltage range; sequentially turn on the plurality of first transistors when the pad voltage increases above the nominal voltage range; and sequentially turn on the plurality of second transistors when the pad voltage decreases below the nominal voltage range.