Programmable input/output interface circuit with five operation modes

This paper presents a programmable input/output interface circuit for some types of field programmable gate array (FPGA) devices which may be used in relatively high voltage (e.g. 5.5V) environments. The proposed circuit provides five different operation modes so that these FPGA devices are capable of connecting with multiple types of IC devices, including high voltage devices and PCI devices. In the proposed circuit, various circuit techniques are used to eliminate gate-oxide overstress and Pad to output supply (Vcco) leakage current when these FPGA devices connect with high voltage devices, and to ensure that over-voltage and under-voltage at Pad is avoidable when these FPGA devices connect with PCI devices. The proposed circuit can be used as an interface IP and had been successfully applied in a 200MHz SRAM-based FPGA device using both 2.5V and 3.3V MOS transistors in a 0.25um CMOS process with dual-oxide option.