Patent ID: 7498845

Claim:
An integrated circuit, comprising: an enable input terminal that is physically accessible externally of the integrated circuit; first and second power supply nodes; functional circuitry that can perform a desired operation, said functional circuitry coupled to said first and second power supply nodes and coupled to said enable input terminal; said enable input terminal receiving an enable signal that is activated when said functional circuitry is to be enabled to perform said desired operation and is deactivated when said functional circuitry is to be disabled from performing said desired operation; and a first switch coupled between said functional circuitry and one of said power supply nodes, said first switch having a control input coupled to said enable input terminal, said first switch isolating said functional circuitry from said one power supply node in response to deactivation of said enable signal and coupling said functional circuitry to said one power supply node in response to activation of said enable signal, wherein said functional circuitry includes a reference voltage circuit that provides a reference voltage, said reference voltage circuit including a transistor having a collector defined by a substrate of the integrated circuit and having a base, the integrated circuit further including a second switch connected between said base and said collector, said second switch having a control input coupled to said enable input terminal, said second switch disconnecting said base from said collector in response to deactivation of said enable signal and connecting said base to said collector in response to activation of said enable signal.