Overvoltage tolerant integrated circuit input/output interface

摘要

An I/O interface circuit which is capable of tolerating the application of an overvoltage condition to a corresponding I/O pad but which also has a relatively low trip point voltage includes an overvoltage detection circuit configured to have a trip point at a first voltage provided by a voltage divider circuit. The voltage divider circuit may include a pair of transistors coupled in series between a voltage source having a second voltage and ground. In such cases, the first voltage may be approximately equal to the difference between the second voltage and a threshold voltage of one of the pair of transistors. Alternatively, the voltage divider circuit may include a NAND gate having an output coupled to the overvoltage detection circuit and an input coupled to receive a second voltage. The second voltage may be determined by a voltage at an I/O pad of the I/O interface and one or more diodes coupled between the I/O pad and the NAND gate.