An apparatus, comprising: an arrangement of master-slave communication interfaces (612, 642, 644, 654, 664); a first die; at least one additional die; a top-level power management circuit disposed on the first die, the top-level power management circuit including a first master communication interface; a system disposed on the additional die, the system including: a system-level power management circuit having: a first slave communication interface communicatively coupled to the first master communication interface; and a second master communication interface communicatively coupled to the first slave communication interface; at least one sub-system circuit (650, 660) having: a sub-system-level power management circuit (652, 654) comprising a second slave communication interface (654, 664) communicatively coupled to the second master communication interface, wherein the sub-system-level power management circuit (652, 654) is adapted to communicate, via the second slave communication interface (654, 664) and via the second master communication interface, data with the system-level power management circuit; and wherein the system-level power management circuit is adapted to communicate power-related parameter data with the top-level power management circuit via the first slave communication interface and the first master communication interface. an arrangement of master-slave communication interfaces (612, 642, 644, 654, 664); a first die; at least one additional die; a top-level power management circuit disposed on the first die, the top-level power management circuit including a first master communication interface; a system disposed on the additional die, the system including: a system-level power management circuit having: a first slave communication interface communicatively coupled to the first master communication interface; and a second master communication interface communicatively coupled to the first slave communication interface; at least one sub-system circuit (650, 660) having: a sub-system-level power management circuit (652, 654) comprising a second slave communication interface (654, 664) communicatively coupled to the second master communication interface, a system-level power management circuit having: a first slave communication interface communicatively coupled to the first master communication interface; and a second master communication interface communicatively coupled to the first slave communication interface; a first slave communication interface communicatively coupled to the first master communication interface; and a second master communication interface communicatively coupled to the first slave communication interface; at least one sub-system circuit (650, 660) having: a sub-system-level power management circuit (652, 654) comprising a second slave communication interface (654, 664) communicatively coupled to the second master communication interface, a sub-system-level power management circuit (652, 654) comprising a second slave communication interface (654, 664) communicatively coupled to the second master communication interface, wherein the sub-system-level power management circuit (652, 654) is adapted to communicate, via the second slave communication interface (654, 664) and via the second master communication interface, data with the system-level power management circuit; and wherein the system-level power management circuit is adapted to communicate power-related parameter data with the top-level power management circuit via the first slave communication interface and the first master communication interface.