PROTECTION CIRCUIT, INTERFACE CIRCUIT, AND COMMUNICATION SYSTEM

摘要

A protection circuit includes a control circuit coupled to a first power-supply wire applied with a first power-supply voltage. The control circuit generates a control voltage in accordance with the first power-supply voltage and an input voltage. A voltage limitation circuit is coupled between a first node applied with the input voltage and a second power-supply wire applied with a second power-supply voltage. The voltage limitation circuit includes a variable resistance unit having a resistance value that changes according to the control voltage. When the first power-supply voltage is not supplied to the protection circuit and the input voltage is larger than a first voltage, the control circuit generates the control voltage such that the resistance value of the variable resistance unit is smaller than that in a case where the input voltage is equal to or less than the first voltage.