Patent ID: 7782701

Claim:
A power gating circuit for gradually increasing the voltage level of an internal power supply voltage bus to the voltage level of a power supply voltage VDD, comprising: a power gating unit that includes first and second power gating transistors connected in parallel between the power supply voltage VDD and the internal power supply voltage bus, wherein the first and second power gating transistors are configured to sequentially turn ON; wherein the first power gating transistor is turned ON in response to a power-down enable signal; wherein the second power gating transistor is turned ON in response to a first intermediate voltage level on the internal power supply voltage bus; wherein the power gating unit further includes a third power gating transistor connected in parallel between the power supply voltage VDD and the internal power supply voltage bus; wherein the first, second and third power gating transistors are configured to sequentially turn ON; wherein the third power gating transistor is turned ON in response to a second intermediate voltage level on the internal power supply voltage bus; and wherein the second intermediate voltage level is higher than the first intermediate voltage level, and the second intermediate voltage level is lower than the power supply voltage VDD.