Abstract: The invention concerns a supply circuitry system and method, including a supply circuitry arranged to control a power-up phase at the end of a sleep period of a circuit region of an integrated circuit, the supply circuitry comprising: first and second switches coupled between a supply rail and a supply node of the circuit region, the supply rail being coupled to receive a supply voltage (VDD) from a power supply unit; a comparator arranged to provide an output based on a comparison between a voltage at the supply node (VDD_INT) and a reference voltage (VREF); and control circuitry coupled to control terminals of the first and second switches and arranged to activate the first switch at the start of the power-up phase, and to activate the second switch once the output of the comparator indicates that the voltage at the supply node is greater than the reference voltage.