Pixel driving circuit and method of driving the same

• US 20070029465A1
• Filed: 05/17/2006
• Published: 02/08/2007
• Est. Priority Date: 06/08/2005
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Choi, Sung-Ho, Kim, Young-Chan, Kim, Yi-Tae, Kong, Hae-Kyung
• Granted Patent: US 7,573,013 B2
• Time in Patent Office: Days
• US Class Current: 250/208.100
• CPC Class Codes: H04N 25/766 comprising control or output lines used for a plurality of functions, e.g. for pixel output, driving, reset or power
• CPC Class Codes: H04N 3/155 Control of the image-sensor operation, e.g. image processing within the image-sensor

Abstract

Contacts and/or a transistor are shared by neighboring pixel circuits in an image sensor. In addition, a common interconnect line provides common control signals for minimizing metal wiring. Such minimization of space for the shared contacts, transistor, and control signals enhances the fill factor of photodiodes in the image sensor.

Claims

1. A pixel circuit of an image sensor, the pixel circuit comprising:

a reset transistor having a reset drain/source contact that is shared with a first neighboring pixel circuit;

a source follower transistor having a source follower drain/source contact that is shared with a second neighboring pixel circuit; and

an interconnect line coupled to the reset drain/source contact and the source follower drain/source contact, and adapted to provide a common toggled control signal there-on.

2. The pixel circuit of claim 1, wherein the common toggled control signal is initially deactivated to logic low, and then is activated to logic high during a reset signal readout and an image signal readout from the pixel circuit.

3. The pixel circuit of claim 1, wherein the first neighboring pixel circuit and the second neighboring pixel circuit are disposed on opposite sides of the pixel circuit.

4. The pixel circuit of claim 1, further comprising:

a photodiode for converting incident light to an electrical signal; and

a transfer transistor coupled to the photodiode for transmitting the electrical signal from the photodiode during an image signal readout from the pixel circuit.

5. The pixel circuit of claim 1, wherein the first neighboring pixel circuit has a corresponding reset transistor coupled to the reset drain/source contact, and wherein the second neighboring pixel circuit has a corresponding source follower transistor coupled to the source follower drain/source contact.

6. The pixel circuit of claim 1, wherein the pixel circuit and the first neighboring pixel circuit are laid out symmetrically.

7. The pixel circuit of claim 6, wherein the pixel circuit and the second neighboring pixel circuit are laid out symmetrically.

8. A method of driving a pixel circuit in an image sensor, comprising:

supplying a common toggled control signal to a reset drain/source contact shared between the pixel circuit and a first neighboring pixel circuit;

supplying the common toggled control signal to a source follower drain/source contact shared between the pixel circuit and a second neighboring pixel circuit; and

generating the common toggled control signal onto an interconnect line coupled to the reset drain/source contact and the source follower drain/source contact.

9. The method of claim 8, further comprising:

initially deactivating the common toggled control signal to logic low; and

activating the common toggled control signal to logic high during a reset signal readout and an image signal readout from the pixel circuit.

10. The method of claim 8, further comprising:

forming the reset drain/source contact to be coupled to reset transistors of the pixel circuit and the first neighboring pixel circuit; and

forming the source follower drain/source contact to be coupled to source follower transistors of the pixel circuit and the second neighboring pixel circuit.

11. The method of claim 8, further comprising:

forming the first neighboring pixel circuit and the second neighboring pixel circuit to be disposed on opposite sides of the pixel circuit.

12. The method of claim 8, further comprising:

converting incident light to an electrical signal at a photodiode of the pixel circuit; and

transmitting the electrical signal from the photodiode during an image signal readout from the pixel circuit.

13. The method of claim 8, further comprising:

laying out the pixel circuit and the first neighboring pixel circuit to be symmetrical.

14. The method of claim 13, further comprising:

laying out the pixel circuit and the second neighboring pixel circuit to be symmetrical.

15. A pixel driver in an image sensor, the pixel driver comprising:

a first pixel circuit for driving a first photodiode;

a second pixel circuit for driving a second photodiode; and

a common overflow device coupled to the first and second pixel circuits for coupling the first and second photodiodes to a power supply node.

16. The pixel driver of claim 15, wherein the common overflow device is adapted to initially be turned off during a global shutter operation, and then turned on during an image signal readout and a reset signal readout from the first and second pixel circuits.

17. The pixel driver of claim 15, wherein the common overflow device is a field effect transistor.

18. The pixel driver of claim 15, wherein the power supply node is a reset drain/source contact shared between the first and second pixel circuits.

19. The pixel driver of claim 18, wherein the reset drain/source contact has applied thereon a control signal that is toggled for a rolling shutter operation and that is set at a logic high state for a global shutter operation.

20. The pixel driver of claim 19, wherein the common overflow device is turned off during the rolling shutter operation.