Zener diode protects FPGA inputs

摘要

Although 5V-powered logic is still common in many applications, most FPGAs support interface levels of 3.3V and lower. When you connect an FPGA to higher voltage levels, the FPGA's application notes commonly suggest that you use the PCI (Peripheral Component Interconnect)-bus clamp diodes in the FPGA's I/O blocks with an external series-limiting resistor to prevent damage to the FPGA (Figure 1).