A method and apparatus for powering up an integrated circuit (IC). An IC includes a plurality of power domains each coupled to receive power from one of a plurality of power sources. Each power domain includes a power-sensing unit. A power-sensing unit in a first one of the plurality of power domains is coupled to receive a first power ok signal from an upstream power domain, and is configured to assert a second power ok signal to be provided to a second power domain. A power-sensing unit in the second power domain is coupled to detect the presence of voltage in the first power domain, and to receive the first power ok signal. When the power-sensing unit in the second power domain has both sensed the presence of power in the first power domain and received the second power ok signal, a third power ok signal is asserted.