0.9 V to 5 V Bidirectional Mixed-Voltage I/O Buffer With an ESD Protection Output Stage

A 0.9 V to 5 V (0.9/1.2/1.8/2.5/3.3/5 V) mixed-voltage I/O buffer with NMOS clamping technique is proposed. By using a dynamic gate bias generator to provide appropriate gate drive voltages for the output stage, the I/O buffer can transmit a sub-3 × VDD voltage-level signal without gate-oxide overstress hazard. Besides, the leakage current is eliminated by adopting a floating N-well circuit. The maximum data rate is measured at 66 MHz for 5/3.3/2.5/1.8/1.2/0.9 V with an equivalent probe capacitive load of 10 pF.