Methods to control the droop when powering dual mode processors and associated circuits

• US 20040090217A1
• Filed: 09/23/2003
• Published: 05/13/2004
• Est. Priority Date: 03/27/2000
• Status: Active Grant

• Current Assignee: Intersil Corporation (Renesas Electronics Corporation)
• Original Assignee: Intersil Corporation (Renesas Electronics Corporation)
• Inventors: Wiktor, Wlodzimerz S., Muratov, Volodymyr A., Coletta, Michael
• Granted Patent: US 6,919,715 B2
• Time in Patent Office: Days
• US Class Current: 323/282
• CPC Class Codes: G06F 1/26 Power supply means, e.g. regulation thereof for memories G11C
• CPC Class Codes: G06F 1/32 Means for saving power
• CPC Class Codes: G06F 1/324 by lowering clock frequency
• CPC Class Codes: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management

Abstract

A DC/DC converter 100 has a DAC 40 that receives a code associated with desired processor operating voltage and sets the reference voltage on its output 41. The reference voltage (V_DAC) is boosted by the buffer amplifier 42 to center the droop along the median load. A sensed current signal I_CS 22 is proportional to the load current I_o 24 and can be either inductor current, or switch current, or diode (or synchronous switch) current. In all cases it is scaled down by the factor of gain G_c. A droop control feedback circuit includes an error amplifier 50. It has two inputs. In one embodiment the gain of the converter is by a signal inversely proportional to the processor clock frequency F_{CPU max} and transformed to the current I_DROOP 32 that creates the voltage drop across the resistor R1. The other input is coupled to the buffer amplifier output. As a result, the output voltage of the converter 50 is inversely proportionally to the load current and is invariant to the processor clock frequency changes associated with the processor mode switchover. Other embodiments modify the gain of the error amplifier, or offset the gain and hold the amount of droop constant.

Claims

1. A method of operating a DC/DC converter having an output coupled to a load with two or more modes of operations, the method comprising:

selectively coupling a power source from two or more power sources to an input of the DC/DC converter; and

creating a droop in an output signal to the load in response in part to a signal from the power source and in response in part to the operating mode of the load such that the amount of droop in the output signal is based on the operating mode of the load.

2. The method of claim 1, wherein creating the droop in the output signal further comprises:

multiplying a sensed current in a feedback loop with a signal that is inversely proportional to a frequency of the load.

3. The method of claim 1, wherein creating the droop in the output signal further comprises:

multiplying a sensed current in a feedback loop with a signal that is inversely proportional to a reference voltage, wherein the reference voltage is associated with a desired operating voltage of the load.

4. The method of claim 1, wherein creating the droop in the output signal further comprises:

multiplying a sensed current in a feedback loop with a signal inversely proportional to a reference voltage and a signal inversely proportional to a frequency in which the load operates, wherein the reference voltage is reflective of a desired operating voltage of the load.

5. The method of claim 1, wherein creating the droop in the output signal further comprises:

multiplying a sensed current in a feedback loop with a signal that is inversely proportional to a reference voltage squared, wherein the reference voltage is reflective of a desired operating voltage of the load.

6. The method of claim 1, wherein creating the droop in the output signal further comprises:

controlling a gain of a buffer amplifier in a feedback loop with a frequency signal proportional to the frequency in which the load operates.

7. The method of claim 6, wherein the frequency signal is derived from a reference voltage, wherein the reference voltage is associated with a desired operating voltage of the load.