Driving circuit adapted for use in optical mice

• US 20070268254A1
• Filed: 05/22/2006
• Published: 11/22/2007
• Est. Priority Date: 05/22/2006
• Status: Active Grant

• Current Assignee: PixArt Imaging Incorporated
• Original Assignee: Avago Technologies General IP PTE Limited (Broadcom, Inc.)
• Inventors: Cheah, Chiang Sun, Tan, Shan Chong, Poh, Ju Chin
• Granted Patent: US 7,737,949 B2
• Time in Patent Office: Days
• US Class Current: 345/166
• CPC Class Codes: G06F 3/0317 in co-operation with a patterned surface, e.g. absolute position or relative movement detection for an optical mouse or pen positioned with respect to a coded surface
• CPC Class Codes: G06F 3/038 Control and interface arrangements therefor, e.g. drivers or device-embedded control circuitry

Abstract

A control circuit having a drive circuit and a controller adapted for use in optical mice is disclosed. The drive circuit is connected between first and second ports and passes a current between those ports having an amplitude determined by a control signal that is generated by the controller. The first port is connected to an illumination device and the second port is connected to a power rail. The control circuit also includes a potential measuring circuit that generates a signal indicative of a drive circuit potential between the first and second ports. The controller records the drive circuit potential for a predetermined current when the first port is connected to an illumination device. The controller sets the control signal based on the recorded drive circuit potential. The control circuit can record the drive circuit potential when the controller is powered.

Claims

1. A control circuit comprising:

a first port for connecting an illumination device;

a second port connecting said control circuit to a power supply;

a drive circuit connected to said first port, said drive circuit passing a current between said first port and said second port having an amplitude determined by a control signal connected thereto;

a potential measuring circuit that generates a signal indicative of a drive circuit potential between said first and second ports; and

a controller that generates said control signal,

wherein said controller records said drive circuit potential for a predetermined current when said first port is connected to an illumination device and said controller sets said control signal based on said recorded drive circuit potential.

2. The control circuit of claim 1 wherein said controller determines an impedance for said illumination device and compares that impedance to impedance values in a table stored in said controller.

3. The control circuit of claim 2 wherein said impedance is determined by measuring said drive circuit potential when first and second currents are caused to flow through said illumination device.

4. The control circuit of claim 1 wherein said controller records said drive circuit potential when said controller is powered on.

5. The control circuit of claim 2 wherein said controller sets said control signal to a first value if said impedance is greater than a predetermined value and to a second value if said impedance value is less than said predetermined value.

6. The control circuit of claim 5 wherein said current passed by said drive circuit when said control signal has said first value is less than said current passed by said drive circuit when said control signal has said second value.

7. The control circuit of claim 1 further comprising an imaging port for receiving an image recorded by a photodiode array, wherein said controller determines a displacement value for a pointing device containing said control circuit and said photodiode array based on said received image.

8. The control circuit of claim 7 wherein said control circuit is contained in a single die.