A CMOS output cell with multiple output modes is disclosed. In one
embodiment, the cell drives a differential output signal on two output
pads in one mode and two single-ended output signals on the two output
pads in another mode. Differential and single-ended driver transistors
are included for this purpose. A logic circuit disables unused driver
transistors, and supplies appropriate drive signals to those transistors
for each mode. When disabled, the driver transistors serve an
electrostatic discharge (ESD) protection function, at least partially
alleviating the need for ESD-specific devices in the cell. The diminished
need for ESD-specific devices allows the cell to offer a highly flexible
chip interface, with little or no increase in circuit area over a
conventional cell that offers only single-ended or differential output.