Semiconductor integrated circuit and operating method thereof

摘要

A semiconductor integrated circuit and its operating method are provided. The present circuit has first and second supply terminals capable of supplying first and second power supply voltages respectively, an input voltage selection circuit coupled to the first and second supply terminals, and first and second power supply switches. The input voltage selection circuit includes a power-on reset circuit, an input voltage detection circuit and a control circuit. When the supply of the first or second power supply voltage to one of both supply terminals is detected upon completion of a power on reset operation, one of both power supply switches and the other thereof are controlled to on and off respectively. When the supply of both power supply voltages to both supply terminals is detected, the one thereof and the other thereof are respectively controlled to on and off according to the preset order of precedence.

主权项

1. A semiconductor integrated circuit comprising:
a first supply terminal capable of supplying a first power supply voltage; a second supply terminal capable of supplying a second power supply voltage; an input voltage selection circuit coupled to the first supply terminal and the second supply terminal; a first power supply switch; and a second power supply switch, wherein the input voltage selection circuit includes a power-on reset circuit, an input voltage detection circuit and a control circuit, wherein in response to the supply of the first power supply voltage to the first supply terminal and the supply of the second power supply voltage to the second supply terminal, the power-on reset circuit generates a power on reset signal, wherein the input voltage detection circuit generates a first voltage detection output signal in response to the supply of the first power supply voltage to the first supply terminal and generates a second voltage detection output signal in response to the supply of the second power supply voltage to the second supply terminal, wherein the control circuit controls the first power supply switch and the second power supply switch in response to the power on reset signal, the first voltage detection output signal and the second voltage detection output signal, wherein the input voltage detection circuit detects the supply of the first power supply voltage to the first supply terminal and the supply of the second power supply voltage to the second supply terminal at a timing of a change in the level of the power on reset signal responsive to the end of a power on reset operation of the power-on reset circuit, wherein in a first case where at the timing of the change in the level of the power on reset signal, the input voltage detection circuit detects the supply of the first power supply voltage to the first supply terminal but does not detect the supply of the second power supply voltage to the second supply terminal, the control circuit controls the first power supply switch and the second power supply switch to an on state and an off state respectively after the end of the power on reset operation, wherein the first power supply switch controlled to the on state supplies the first power supply voltage supplied to the first supply terminal to a load by the control of the first power supply switch and the second power supply switch to the on state and the off state respectively after the end of the power on reset operation, wherein in a second case where at the timing of the change in the level of the power on reset signal, the input voltage detection circuit detects the supply of the second power supply voltage to the second supply terminal but does not detect the supply of the first power supply voltage to the first supply terminal, the control circuit controls the first power supply switch and the second power supply switch to an off state and an on state respectively after the end of the power on reset operation, wherein the second power supply switch controlled to the on state supplies the second power supply voltage supplied to the second supply terminal to the load by the control of the first power supply switch and the second power supply switch to the off state and the on state respectively after the end of the power on reset operation, wherein in a third case where at the timing of the change in the level of the power on reset signal, the input voltage detection circuit detects the supply of the first power supply voltage to the first supply terminal and the supply of the second power supply voltage to the second supply terminal, the control circuit controls one of the first power supply switch and the second power supply switch and the other thereof to an on state and an off state respectively after the end of the power on reset operation, wherein in the third case, the one of the first power supply switch and the second power supply switch and the other thereof are respectively controlled to the on state and the off state in accordance with the order of precedence set to the control circuit in advance, and wherein the one thereof controlled to the on state supplies the first power supply voltage or the second power supply voltage supplied to the first supply terminal or the second supply terminal to the load.