Semiconductor integrated circuit with input buffer having high voltage protection

Abstract

A high voltage reception terminal is formed in a semiconductor integrated circuit without increasing the number of manufacturing processes and the manufacturing cost. A transfer gate configured from a NMOS, which is the high withstand voltage transistor, and a pull-up resistor are formed. An input terminal of the transfer gate is connected to the high voltage reception terminal and an output terminal of the transfer gate is connected to a CMOS inverter through an input resistor. One end of the pull-up resistor is connected to the output terminal of the transfer gate and the other end of the pull-up resistor receives source voltage VDD (5V). The transfer gate lowers the inputted high voltage VX (VX>VDD) to VDD-Vt1'. The pull-up resistor biases the voltage at the output terminal of the transfer gate to VDD and boosts the voltage at the output terminal that has been lowered by the transfer gate to about VDD.