Conditional correlated multiple sampling single slope analog-to-digital converter, and associated image sensor system and method
AssigneeTaiwan Semiconductor Manufacturing Company, Ltd.
InventorsShang-Fu Yeh, Kuo-Yu Chou
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Abstract
A conditional correlated multiple sampling (CCMS) single slope (SS) analog-to-digital converter (ADC) is provided. The CCMS SS ADC includes a comparator, arranged to compare an analog signal with a ramp signal and generate a comparison result; and a CCMS control circuit, arranged to determine a swing of the ramp signal according to a magnitude of the analog signal. An image sensor system using the CCMS SS ADC and a method of CCMS SS analog-to-digital conversion are also disclosed.
Claims20
An analog-to-digital converter (ADC), comprising:
- a comparator, arranged to compare an analog signal with a ramp signal and generate a comparison result;
- a switch, including a first ramp input terminal and a second ramp input terminal arranged to receive a first ramp signal and a second ramp signal respectively, wherein the first ramp signal has a first swing greater than a second swing of the second ramp signal;
- and
- a control circuit, coupled to the comparator and the switch, the control circuit being arranged to receive a signal, and a time period of an assertion of the signal representing a programmable small-swing signal detection region;
- wherein the control circuit controls the switch to output the first ramp signal or the second ramp signal as the ramp signal according to a magnitude of the analog signal and the time period of the assertion of the signal representing the programmable small-swing signal detection region.
An image sensor system, comprising:
- a pixel array, comprising a plurality of pixel cells arranged into rows and columns;
- a bit line coupled to at least one of the pixels within a column of the pixel array;
- an analog-to-digital converter (ADC) coupled to the bit line readout from the at least one pixel, the ADC comprising:
- a control circuit, arranged to receive a signal, and a time period of an assertion of the signal representing a programmable small-swing signal detection region, wherein the control circuit determines whether an analog input pixel is a dark pixel according to a magnitude of the analog signal and the time period of the assertion of the signal representing the programmable small-swing signal detection region;
- and
- a comparator, arranged to compare the analog input pixel with a first ramp signal having a first swing for m times when the analog input pixel is determined to be the dark pixel;
- and compare the analog input pixel with a second ramp signal having a second swing for n times when the analog input pixel is not determined to be the dark pixel;
- wherein the first swing is smaller than the second swing, and m being greater than n;
- and
- an amplifier coupled between the bit line and the ADC, the amplifier configured to amplify a signal on the bit line to generate the analog input pixel.
A method of analog-to-digital conversion, the method comprising:
- receiving a signal, and a predefined time period of an assertion of the signal representing a programmable small-swing signal detection region;
- selectively outputting a first ramp signal or a second ramp signal as a ramp signal according to a magnitude of an analog signal and the predefined time period of the assertion of the signal representing the programmable small-swing signal detection region, wherein the first ramp signal has a first swing greater than a second swing of the second ramp signal;
- comparing the analog signal with the ramp signal and generating a comparison result;
- and
- obtaining an analog-to-digital conversion result according to the comparison result.
Dependencies are inferred from the claim text.