HIGH VOLTAGE TOLERANT INPUT/OUTPUT INTERFACE CIRCUIT

An IO interface circuit for use in a high voltage tolerant application is provided. The IO interface circuit includes a signal pad and at least a first parasitic bipolar transistor having an emitter adapted for connection to a voltage return of the interface circuit, a base adapted to receive a first control signal, and a collector connected directly to the signal pad in an open collector configuration. The interface circuit further includes a MOS control circuit coupled to the parasitic bipolar transistor and being operative to generate the first control signal. The IO interface circuit may further include an active pull-up circuit connected between a voltage supply of the interface circuit and the signal pad.