System and method for selecting between a voltage specified by a processor and an alternate voltage to be supplied to the processor

Abstract

Disclosed herein are a method and apparatus to provide a deterministic power-on voltage in a system having a processor-controlled voltage level. In one embodiment, the system includes a DC/DC converter, a processor, and a selection circuit. The DC/DC converter receives a voltage setting signal or signals from the selection circuit and provides an adjustable power output signal having a voltage indicated by the voltage setting signal. The processor is powered by the adjustable power output signal. When powered, the processor provides a programmable voltage setting signal or signals. The selection circuit receives the programmable voltage setting signal or signals, a hardwired voltage setting signal, and a selection signal or signals, and when the selection signal is in a predetermined condition, the selection circuit provides the programmable voltage setting signal or signals from the processor to the DC/DC converter. Preferably, when the selection signal is in a second predetermined condition complementary to the first predetermined condition, the circuit provides the hardwired voltage setting signal to the DC/DC converter. The first and second predetermined conditions of the selection signal are preferably de-assertion and assertion, respectively. The selection signal may be determined by a logic gate that combines a mode control signal and a power good signal, and causes the selection signal to select the voltage setting signal from the processor only when the power good signal is asserted and the mode control signal is de-asserted. This advantageously allows for the processor to dictate its operating voltage level, an ability that is extremely useful for power and thermal management in notebook PCs.

Dependencies are inferred from the claim text.