US Patent 10908667 Technique for managing power domains in an integrated circuit

An integrated circuit and method are provided for managing power domains. The integrated circuit has first circuitry provided within a first power domain, and a distributed power controller for controlling transition of the first power domain between a plurality of power states. The distributed power controller comprises at least power control circuitry in a second power domain and additional power control circuitry in a third power domain. Whilst the current power state of the first power domain is in any one of at least two of the plurality of power states, the second power domain is allowed to be placed in a power saving state where the power control circuitry loses knowledge of the current power state of the first power domain. However, the third power domain is prevented from entering that power saving state. Further, the additional power control circuitry is arranged to output a mode status signal that is then used by the power control circuitry, when the second power domain exits the power saving state, to place the power control circuitry into an initial mode of operation that is dependent on the current power state of the first power domain. This ensures that, despite the power control circuitry losing knowledge of the current power state of the first power domain whilst it is in the power saving state, no unintended consequences occur when the second power domain subsequently exits the power saving state.