High swing interface output stage integrated circuit for interfacing a device with a data bus

A method for providing a high swing interface output stage integrated circuit for interfacing a device with a data bus, wherein other devices on the data bus may operate at supply voltages outside the supply voltage of the interface circuit, the method comprising the steps of

• providing a bipolar junction transistor coupled between a first supply rail and an output terminal of the circuit,
• providing first, second and third field effect transistors of Pwell or Nwell type corresponding to the P or N type of the base of the bipolar junction transistor, respectively, the first and second field effect transistors being coupled in series between the output terminal and a second supply rail of the circuit, the second field effect transistor being coupled to the second supply rail, the third field effect transistor being coupled between the common connection of the first and second field effect transistors and the gate of the second field effect transistor for holding the second field effect transistor off when the polarity of the voltage across the source and drain of the second field effect transistor is reversed from that normally established by voltages sourced to the first and second supply rails, the common connection of the first, second and third field effect transistors being connected to the well or wells of the respective first, second and third field effect transistors, and
• controlling the third field effect transistor for holding the second field effect transistor on when the circuit is powered up and active so that the bipolar junction transistor and the first field effect transistor can be controlled for determining the high and low states of the output terminal, and for controlling the third field effect transistor, when the circuit is powered down or powered up and active or inactive for holding the second field effect transistor off to present a high impedance between the output terminal and the second supply rail in response to the voltage on the output terminal being driven outside supply voltages presented on the first and second rails in the direction of the second rail, and
• adapting the bipolar junction transistor, the first and second field effect transistors and the control circuit so that when the circuit is powered up and active the bipolar junction transistor forms one of a high impedance or a current limiting impedance between the output terminal and the first supply rail when the voltage on the output terminal is driven outside the supply voltage on the first and second rails in the direction of the second rail, and so that the first field effect transistor forms a current limiting impedance between the output terminal and the second supply rail when the voltage on the output terminal is driven outside the supply voltage on the first and second rails in the direction of the first rail.