An integrated circuit comprises a power supply input pin for receiving an off-chip supply voltage which can have a variable current, an on-chip power source to be powered by the off-chip supply voltage and which can provide a regulated current, a set of one or more circuits to be powered by at least one of the off-chip supply voltage and the on-chip power source, a configuration memory storing a set of one or more memory settings that indicate whether a circuit of said set of one or more circuits is powered by the on-chip power source, and control circuitry responsive to the at least one memory setting to control whether said circuit of said set of one or more circuits is powered by the on-chip power source.