Digital power management system

• US 5,784,051 A
• Filed: 01/27/1997
• Issued: 07/21/1998
• Est. Priority Date: 01/27/1997
• Status: Expired due to Fees

• Current Assignee: VLSI Technology, Inc. (Koninklijke Philips N.V.)
• Original Assignee: VLSI Technology, Inc. (Koninklijke Philips N.V.)
• Inventors: Harrow, Scott E., Nalubola, Rishi
• Primary Examiner(s): Bayerl, Raymond J.
• Assistant Examiner(s): Luu, Matthew
• Application Number:
  US08/788,847
• Time in Patent Office: 540 Days
• Field of Search: 345/156, 345/157, 345/159, 345/161, 345/162, 345/163, 273/148 B, 74/471 XY
• US Class Current: 345/161
• CPC Class Codes: G06F 1/3215 Monitoring of peripheral devices
• CPC Class Codes: G06F 1/3259 Power saving in cursor control device, e.g. mouse, joystick, trackball
• CPC Class Codes: G06F 3/0383 Signal control means within the pointing device
• CPC Class Codes: G06F 3/05 Digital input using the sampling of an analogue quantity at regular intervals of time , input from a/d converter or output to d/a converter
• CPC Class Codes: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management

Abstract

A digital power management system for an analog-to-digital converter operates to cause the sample rate of the analog-to-digital converter to function at an original desired frequency so long as changing input signals are present. Whenever activity at the input of the analog-to-digital converter ceases to change, the system automatically decreases the clock signal sampling rate to a slower clock frequency, or shuts down the application of clock signals. This conserves power until a change in the analog input is detected, whereupon the system automatically increases the sample clock frequency back to the original frequency.

Claims

1. A digital power management system including in combination:

a source of analog signals;

an analog-to-digital converter (ADC) coupled to receive signals from said source of analog signals, operated by clock pulses applied thereto, and providing a digital output signal;

a source of clock signals coupled with said analog-to-digital converter for operating said analog-to-digital converter to sample said analog signals at the frequency of said clock signals;

a register coupled with said analog-to-digital converter for receiving and storing said digital output signals;

comparison logic coupled with said register for detecting a change in said digital signals stored in said register;

a timeout counter coupled with said comparison logic and reset thereby each time a change in said digital signals stored in said register is detected by said comparison logic;

said timeout counter producing an output signal a predetermined time interval after reset; and

a clock control circuit coupled with said source of clock signals and with said timeout counter to reduce-the frequency of said clock signals in response to an output signal from said timeout counter indicative of no change in said digital signals stored in said register over said predetermined time interval to reduce the power consumed by said system.

2. The combination according to claim 1 wherein said clock control circuit comprises a programmable clock divider.

3. The combination according to claim 2 wherein said source of clock signals supplies clock signals at at predetermined frequency and said programmable clock divider supplies clock signals at a frequency which is a fraction of said predetermined frequency.

4. The combination according to claim 3 wherein said source of analog signals is a source of variable voltage signals.

5. The combination according to claim 4 wherein said source of analog signals comprises a joystick potentiometer.

6. The combination according to claim 2 wherein said programmable clock divider operates to block the application of clock signals from said source of clock signals to said analog-to-digital converter in response to an output signal from said timeout counter.

7. The combination according to claim 6 wherein said source of analog signals is a source of variable voltage signals.

8. The combination according to claim 7 wherein said source of analog signals comprises a joystick potentiometer.

9. The combination according to claim 1 wherein said source of analog signals is a source of variable voltage signals.

10. The combination according to claim 9 wherein said source of analog signals comprises a joystick potentiometer.