Column comparator system and method for comparing a ramping signal and an input signal

Patent metadata

Field	Value
Publication number	US-9906745-B2
Application number	US-201414561015-A
Country	US
Kind code	B2
Filing date	Dec 4, 2014
Priority date	Dec 12, 2013
Publication date	Feb 27, 2018
Grant date	Feb 27, 2018

Abstract

A system and method is provided for image sensing. The image sensing system includes a comparator for comparing an input signal representing a sensed light signal from at least one pixel of the image sensing system and a reference signal. The comparator includes at least one digital transistor.

First claim

What is claimed is:

1. An image sensing system comprising:
a comparator for comparing an input signal representing a sensed light signal from at least one pixel of the image sensing system and a reference signal, the comparator including at least one digital transistor, wherein the comparator includes a charge sharing circuit for generating a first amplifier input signal based on at least the input signal, the first amplifier input signal having a signal range that is reduced from the signal range of the input signal; and
a controller electrically coupled to the comparator, wherein the controller is configured to:
receive a signal representing a signal path gain of the comparator,
adjust a reduction ratio of the input signal by configuring the charge sharing circuit,
determine whether a signal range reduction ratio compensation is required,
in response to determining that the signal range reduction ratio compensation is required, determine an amount of the signal range reduction ratio compensation, and
adjust at least one of a counter frequency or a digital-to-analog converter biasing signal of the image sensing system based on the determined amount of the signal range reduction ratio compensation.

2. The image sensing system of claim 1 , wherein at least one digital transistor has a maximum withstand voltage of about or less than 1.8V.

3. The image sensing system of claim 1 , wherein the charge sharing circuit includes a plurality of capacitors, and wherein the charge sharing circuit is capable of reducing a signal range based on a configuration of the charge sharing circuit.

4. The image sensing system of claim 3 , wherein the plurality of capacitors include a first capacitor, a second capacitor, and a third capacitor, each including a first terminal and a second terminal, the first terminal of the first capacitor being configured to receive the input signal and the first terminal of the third capacitor being configured to receive the reference signal.

5. The image sensing system of claim 4 , wherein the charge sharing circuit further includes a first switch electrically coupled between the first terminals of the first and second capacitors and a second switch electrically coupled between the first terminals of the second and third capacitors.

6. The image sensing system of claim 1 , wherein the controller is further configured to:
determine whether the signal path gain is greater than or equal to a threshold gain;
when the signal path gain is greater than or equal to the threshold gain, configure the charge sharing circuit to reduce the input signal by a first reduction ratio; and
when the signal path gain is less than the threshold gain, configure the charge sharing circuit to reduce the input signal by a second reduction ratio, the second reduction ratio being greater than the first reduction ratio.

7. The image sensing system of claim 1 , wherein configuring the charge sharing circuit is based on at least one of a pre-defined gain-switch map or a pre-defined equation.

8. The image sensing system of claim 1 , wherein the comparator includes a first amplifier having at least one digital transistor, the first amplifier being electrically coupled to the charge sharing circuit for generating a first amplifier output signal based on the first amplifier input signal.

9. The image sensing system of claim 8 , wherein the comparator further includes a second amplifier, the second amplifier being electrically coupled to the first amplifier for generating a second amplifier output signal based on the first amplifier output signal, wherein an amplifier gain of the second amplifier is adjustable based on a signal path gain of the comparator circuit.

10. The image sensing system of claim 9 , wherein the comparator further includes a third amplifier, the third amplifier being electrically coupled to the second amplifier for generating a third amplifier output signal based on the second amplifier output signal.

11. The image sensing system of claim 1 , further comprising a ramp signal generator electrically coupled to the comparator for generating the reference signal, wherein the ramp signal generator includes a counter, a bias generator, and a digital to analog converter.

12. An image sensing system comprising:
a comparator for comparing an input signal representing a sensed light signal from at least one pixel of the image sensing system and a reference signal, the comparator including a charge sharing circuit for reducing a signal range of the input signal; and
a controller electrically coupled to the comparator, wherein the controller is configured to:
receive a signal representing a signal path gain of the comparator,
adjust a reduction ratio of the input signal by configuring the charge sharing circuit,
determine whether a signal range reduction ratio compensation is required,
in response to determining that the signal range reduction ratio compensation is required, determine an amount of the signal range reduction ratio compensation, and
adjust at least one of a counter frequency or a digital-to-analog converter biasing signal of the image sensing system based on the determined amount of the signal range reduction ratio compensation.

13. The image sensing system of claim 12 , wherein the comparator includes at least one digital transistor.

14. The image sensing system of claim 13 , wherein the at least one digital transistor has a maximum withstand voltage of about or less than 1.8V.

15. The image sensing system of claim 12 , wherein the charge sharing circuit includes a plurality of capacitors, and wherein the charge sharing circuit is capable of reducing the signal range based on a configuration of the charge sharing circuit.

16. The image sensing system of claim 12 , wherein the comparator includes a first amplifier having at least one digital transistor, the first amplifier being electrically coupled to the charge sharing circuit.

17. A method for comparing a reference signal and an input signal representing a sensed light signal from at least one pixel of an image sensing system, the method comprising:
receiving the input signal and the reference signal by a charge sharing circuit;
providing, by the charge sharing circuit, a first amplifier input signal based on at least the input signal and the reference signal;
generating, by a first amplifier having at least one digital transistor, a first amplifier output signal based on the first amplifier input signal;
receiving a signal representing a signal path gain of the comparator;
adjusting a reduction ratio of the input signal by configuring the charge sharing circuit;
determining whether a signal range reduction ratio compensation is required;
in response to determining that the signal range reduction ratio compensation is required, determining an amount of the signal range reduction ratio compensation; and
adjusting at least one of a counter frequency or a digital-to-analog converter biasing signal of the image sensing system based on the determined amount of the signal range reduction ratio compensation.

18. The method of claim 17 , wherein the first amplifier input signal has a signal range that is reduced from the signal range of the input signal based on a configuration of the charge sharing circuit.

Assignees

• Cista Sys Corp

Inventors

• Zhang Guangbin

Classifications

• H04N25/77 Primary

  Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components · CPC title

• H04N5/378

  Electricity · mapped topic

• H03M1/18

  Automatic control for modifying the range of signals the converter can handle, e.g. gain ranging · CPC title

• H04N5/3745 Primary

  Electricity · mapped topic

• H03M1/129

  Means for adapting the input signal to the range the converter can handle, e.g. limiting, pre-scaling (H03M1/18 takes precedence); Out-of-range indication · CPC title