An apparatus, comprising: an arrangement of master-slave communication interfaces ; 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 having: a sub-system-level power management circuit comprising a second slave communication interface communicatively coupled to the second master communication interface , wherein the sub-system-level power management circuit is adapted to communicate, via the second slave communication interface 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 ; 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 having: a sub-system-level power management circuit comprising a second slave communication interface 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 having: a sub-system-level power management circuit comprising a second slave communication interface communicatively coupled to the second master communication interface , a sub-system-level power management circuit comprising a second slave communication interface communicatively coupled to the second master communication interface , wherein the sub-system-level power management circuit is adapted to communicate, via the second slave communication interface 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 . <EOS>