PROTECTION CIRCUIT, INTERFACE CIRCUIT AND COMMUNICATION SYSTEM

摘要

PROBLEM TO BE SOLVED: To provide a protection circuit that can implement protection even when a supply voltage is not supplied.SOLUTION: A protection circuit 43 comprises: a control circuit 44; and a voltage limiting circuit 45. The control circuit 44 has a transistor T11, a resistor R11, a transistor T12 and a resistor R12 connected between high potential side power wiring VD2 and low potential side power wiring VSS. When a supply voltage VD2 is not supplied, the transistor T12 of the control circuit 44 turns on in response to a voltage V (E23) based on a supply voltage VD1 to lower a voltage at a gate terminal of a transistor T13 in a floating state to the level of the power wiring VSS. This lowers an on resistance value of the transistor T13. The voltage limiting circuit 45 thus limits a voltage at a node N1 to a voltage depending on a resistance value of a resistor R13 and the on resistance value of the transistor T13.