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

Patent metadata

Field	Value
Publication number	US-10284802-B2
Application number	US-201815869181-A
Country	US
Kind code	B2
Filing date	Jan 12, 2018
Priority date	Dec 12, 2013
Publication date	May 7, 2019
Grant date	May 7, 2019

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. A sensing system, comprising:
a comparator configured to compare an input signal representing a sensed light signal with a ramping signal; and
a controller coupled to the comparator and configured to:
reduce a signal range of the input signal;
determine an amount of a signal range reduction ratio compensation according to the signal range reduction; 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 sensing system of claim 1 , wherein the comparator including at least one digital transistor having a maximum withstand voltage no more than 1.8V.

3. The sensing system of claim 1 , wherein to compare the input signal representing the sensed light signal with the ramping signal, the comparator is configured to:
combine the input signal and the ramping signal to obtain a combined signal; and
compare the combined signal with a reference signal.

4. The sensing system of claim 1 , wherein:
the comparator includes a charge sharing circuit for generating a first amplifier input signal based on at least the input signal;
the charge sharing circuit includes a plurality of capacitors; and
the charge sharing circuit is configured to reduce the signal range of the input signal based on a configuration of the capacitors to obtain a reduced signal range for the first amplifier input signal.

5. A sensing system, comprising:
a comparator configured to compare an input signal representing a sensed light signal with a ramping signal, wherein:
the comparator comprises a charge sharing circuit and one or more amplifiers connected in a series;
the charge sharing circuit is configured to receive the input signal and the ramping signal to generate a first amplifier input signal based on at least the input signal and the ramping signal; and
the one or more amplifiers in the series are configured to receive the first amplifier input signal and generate an output signal;

a controller configured to generate a control signal based on a signal path gain of the comparator; and
a ramping signal generator coupled to the controller and the comparator, wherein the ramping signal generator is configured to receive the control signal and generate the ramping signal based on the control signal.

6. The sensing system of claim 5 , further comprising:
a pixel grid for sensing the light signals;
a column access circuitry comprising multiple column read circuits each corresponding and being coupled to a column in the pixel grid; and
a plurality of the comparators each coupled to the column read circuit and configured to receive a readout signal from the column read circuit as the input signal.

7. The sensing system of claim 5 , wherein:
the charge sharing circuit is configured to reduce a signal range of the input signal; and
the controller is further configured to adjust a slope of the ramping signal via the control signal based on the signal path gain.

8. The sensing system of claim 7 , wherein:
adjusting the slope of the ramping signal compensates the signal range reduction of the input signal; and
a signal range reduction ratio compensation associated with the adjustment of the ramping signal is the same as a signal range reduction ratio associated with the reduction of the signal range.

9. The sensing system of claim 5 , wherein:
the charge sharing circuit includes a plurality of capacitors; and
the charge sharing circuit is configured to reduce a signal range of the input signal based on configuring at least one of capacitive values of the capacitors or connections among the capacitors.

10. The sensing system of claim 9 , further comprising a controller coupled to the charge sharing circuit and configured to:
receive a signal path gain of the comparator; and
transmit a reduction control signal based on the signal path gain to the charge sharing circuit to effectuate the configuration of at least one of the capacitive values of the capacitors or the connections among the capacitors.

11. The sensing system of claim 5 , wherein:
the one or more amplifiers comprise a first amplifier, a second amplifier, and a third amplifier;
the first amplifier is coupled to the charge sharing circuit for generating a first amplifier output signal based on the first amplifier input signal;
the second amplifier is coupled to the first amplifier for generating a second amplifier output signal based on the first amplifier output signal; and
the third amplifier is coupled to the second amplifier for generating a third amplifier output signal as the output signal based on the second amplifier output signal.

12. The sensing system of claim 11 , further comprising:
the controller coupled to the second amplifier, wherein the controller is configured to transmit a mode control signal to the second amplifier to configure an amplifier gain of the second amplifier based on the signal path gain of the comparator.

13. A sensor system, comprising:
a sensor configured to obtain a sensed light signal;
a plurality of comparators coupled to the sensor;
a ramping signal generator coupled to the comparators; and
a controller coupled to the ramping signal generator and each of the comparators, wherein:
the controller is configured to generate a control signal based on a signal path gain of the comparator;
the ramping signal generator is configured to receive the control signal and generate a ramping signal based on the control signal;
the each comparator is configured to:
receive the ramping signal and an input signal representing the sensed light signal;
compare the input signal with the ramping signal; and
generate an output signal.

14. The sensor system of claim 13 , wherein:
the each comparator comprises a charge sharing circuit and one or more amplifiers connected in a series;
the charge sharing circuit is configured to receive the input signal and the ramping signal to generate a first amplifier input signal based on at least the input signal and the ramping signal; and
the one or more amplifiers in the series are configured to receive the first amplifier input signal and generate the output signal.

15. The sensor system of claim 14 , wherein:
the charge sharing circuit is configured to reduce a signal range of the input signal; and
the controller is further configured to adjust a slope of the ramping signal via the control signal based on the signal path gain.

16. The sensor system of claim 15 , wherein:
adjusting the slope of the ramping signal compensates the signal range reduction of the input signal; and
a signal range reduction ratio compensation associated with the adjustment of the ramping signal is the same as a signal range reduction ratio associated with the reduction of the signal range.

17. The sensor system of claim 14 , wherein:
the charge sharing circuit includes a plurality of capacitors; and
the charge sharing circuit is configured to reduce a signal range of the input signal based on configuring at least one of capacitive values of the capacitors or connections among the capacitors.

18. The sensor system of claim 14 , wherein the controller is coupled to the charge sharing circuit and configured to transmit a reduction control signal based on the signal path gain to the charge sharing circuit to effectuate the configuration of at least one of the capacitive values of the capacitors or the connections among the capacitors.

1

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

• H04N5/3745 Primary

  Electricity · mapped topic

• H03M1/18

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

• 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

• H04N5/378

  Electricity · mapped topic