Patent ID: 7042270

Claim:
An interface system for interfacing two ICs, comprising: a first IC having a push-pull type output circuit coupled between a first supply voltage and the ground, said push pull type output circuit controlled to be ON or OFF by a control signal, and an output terminal for outputting an output signal of said first IC; and a second IC having an input terminal connected to said output terminal of said first IC for receiving said output of said first IC as the input signal to said second IC, an internal circuit having a second power supply voltage higher than said first power supply voltage as an operating voltage, a terminal for supplying said first power supply voltage to said second IC, a buffer circuit connected to said first power supply voltage and the ground, wherein input signal of said input terminal is supplied to said buffer circuit and output signal of said buffer circuit for driving said internal circuit is generated, and a pull-up resistor and a pull up diode connected in series with said pull-up resistor, coupled between said input terminal and said first power supply voltage, wherein said pull-up diode is provided to a direction such that the anode of said pull-up diode is on the side of said first power supply voltage, and the cathode of said pull-up diode is on the side of said input terminal.