Method, system and apparatus to boost pixel floating diffusion node voltage

• US 20090115878A1
• Filed: 11/07/2007
• Published: 05/07/2009
• Est. Priority Date: 11/07/2007
• Status: Abandoned Application

• Current Assignee: Aptina Imaging Corporation (ON Semiconductor Corporation)
• Original Assignee: Micron Technology, Inc.
• Inventors: Mauritzson, Richard A.
• Application Number:
  US11/979,719
• Publication Number:
  US 20090115878A1
• Time in Patent Office: Days
• US Class Current: 348/307
• CPC Class Codes: H04N 25/573 the logarithmic type
• CPC Class Codes: H04N 25/65 applied to reset noise, e.g. KTC noise related to CMOS structures by techniques other than CDS
• CPC Class Codes: H04N 25/76 Addressed sensors, e.g. MOS or CMOS sensors
• CPC Class Codes: H04N 25/77 Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components

Abstract

A method, apparatus and system providing a pixel within an imaging device in which a separate power source is used for resetting a floating diffusion node from a power source used for pixel operating power.

Claims

1. A pixel circuit, comprising:

photo-conversion device for accumulating charge;

a storage region for storing charge accumulated by the photo-conversion device;

a transistor for outputting a signal based on the stored charge, the transistor receiving a first operating voltage;

a device for resetting the storage region by applying a voltage to the storage region, the device receiving a second operating voltage that is higher than the first operating voltage.

2. The pixel circuit of claim 1, wherein the first operating voltage is supplied on a first voltage source line and the second operating voltage is supplied on a second voltage source line.

3. The pixel circuit of claim 2, wherein the device comprises a reset transistor which has a gate and a source/device terminal coupled to the second voltage source line.

4. The pixel circuit of claim 1 wherein the device comprises a diode.

5. The pixel circuit of claim 2 where the device comprises a reset transistor having a first source/drain terminal coupled to the second voltage source line, a second source/drain terminal coupled to the storage region, and a gate for receiving a reset control signal.

6. The pixel circuit of claim 5, further comprising a third transistor for controlling a transfer of charge from the photo-conversion device to the storage region, having a first drain/source connected to the photo-conversion device and a second drain/source connected to the storage region.

7. The pixel circuit of claim 6, further comprising a fourth transistor for selecting the pixel circuit for output, having a first source/drain connected to a source/drain of the second transistor and a second source/drain connected to an output line.

8. The pixel circuit of claim 2, wherein the device for resetting also resets the photo-conversion device, the second voltage source line supplying a first pulsed voltage for resetting the photo-conversion device and a second pulsed voltage for resetting the storage region.

9. The pixel circuit of claim 8, wherein the second pulse voltage is higher than the first pulsed voltage.

10. The pixel circuit of claim 8, further comprising a transfer transistor activated by a control signal for transferring charge from the photo-conversion device to the storage region, the transfer transistor being activated by the control signal during a time when the first pulsed voltage is supplied by the second voltage source line.

11. The pixel circuit of claim 10, wherein the second voltage source line supplies the first voltage pulse signal for some time after the control signal no longer activates the transfer transistor.

12. The pixel circuit of claim 1, wherein the pixel circuit is part of a pixel array of an imager device.

13. The pixel circuit of claim 12, wherein the imager device is part of a digital camera.

14. A method of operating a pixel circuit, the method comprising:

supplying a first voltage from a first voltage source as a reset voltage to a floating diffusion node of the pixel; and

supplying a second voltage from a second voltage source as an operating voltage to a readout circuit of the pixel.

15. A method as in claim 14, wherein the first voltage is of a higher voltage level than the second voltage.

16. A method as in claim 14 further comprising supplying the reset voltage to the floating diffusion node through a reset device.

17. A method as in claim 14, wherein the reset device is a reset transistor having one source/device terminal connected to the floating diffusion node and the first voltage is supplied to a second source/drain terminal of the reset transistor.

18. A method is in claim 17 further comprising supplying the voltage to a gate of the reset transistor.

19. A method as in claim 17 further comprising controlling operation of the reset transistor with a reset control signal support to its gate.

20. A method as in claim 14 wherein the pixel circuit further comprises a photo-conversion device and the supplying of the first voltage comprises supplying the first voltage as a first voltage pulse of a first level to reset the photo-conversion device and the floating diffusion node and supplying the first voltage as a second voltage pulse of a second level, to reset the floating diffusion node.

21. A method as in claim 20 wherein the second level is greater than the first level.

22. A method of claim 21, wherein the pixel circuit further comprises a transfer transistor for transferring charge from the photo-conversion device and the floating diffusion node and the first voltage pulse is supplied during a period when the transfer transistor is on.

23. A method of claim 17 further comprising operating the reset transistor in an anti-blooming mode when the reset transistor is not resetting the floating diffusion region.

24. A method of operating a pixel circuit, the method comprising:

providing an operating voltage for a first readout transistor from a first voltage source; and

resetting a floating diffusion node which is coupled to a gate of the readout transistor by pulsing a reset signal to a gate of a reset transistor from a second voltage source, where the reset signal is applied to both the gate and a drain/source terminal of the reset transistor and has a voltage level which is higher than that of the operating voltage.

25. The method of claim 24, wherein the reset signal is greater than the threshold voltage level of the reset transistor.

26. A method of operating a pixel circuit, the method comprising:

providing an operating voltage to a source-follower transistor from a first voltage source;

providing a reset voltage level to a reset transistor from a second voltage source having a voltage level higher than that of the operating voltage; and

resetting a floating diffusion voltage by pulsing a signal to a gate of a reset transistor from a third voltage source.

27. An imaging device, comprising:

a pixel array, wherein at least one pixel of the pixel array comprises;

a photo-conversion device for accumulating charge;

a storage region for storing charge accumulated by the photo-conversion device;

a first transistor for resetting the storage region charge level, the first transistor having a first source/drain connected to the storage region and a second source/drain connected to a gate of the first transistor and to a first voltage source;

a second transistor for outputting a signal based on the charge stored in the storage region, the second transistor having a gate connected to the storage region and a source/drain connected to a second voltage source, the voltage level supplied by the first voltage source being higher than that supplied by the second voltage source; and

a third transistor for selectively coupling the output of the second transistor to a column line.

28. The imaging device of claim 27, further comprising a fourth transistor for controlling a transfer of charge from the photo-conversion device to the storage region.

29. The imaging device of claim 27, wherein the first voltage source is not a boosted version of the voltage supplied by the second voltage source.