Metal-oxide-semiconductor capacitor based charge sharing successive approximation register data converter
AssigneeSemiconductor Components Industries, LLC
InventorManuel H. Innocent
Life of this patent
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Abstract
An image sensor may include an analog-to-digital converter. The converter may have a input capacitor, one or more metal-oxide-semiconductor capacitors, a digital-to-analog converter, and a comparator. An input signal may be sampled onto the input capacitor while the metal-oxide-semiconductor capacitors are activated. A few conversion steps may be performed while the metal-oxide-semiconductor capacitors are activated. After the few conversion steps, the metal-oxide-semiconductor capacitors are deactivated to realize a voltage gain, which makes the converter less sensitive to comparator noise.
Claims20
An image sensor, comprising:
- an image sensor pixel;
- a column line configured to receive a signal from the image sensor pixel;
- and
- a data converter coupled to the column line, wherein the data converter comprises:
- a first input port;
- a second input port;
- a comparator having a first input coupled to the first input port and having a second input coupled to the second input port;
- a digital-to-analog converter coupled to at least one of the first and second inputs of the comparator;
- a sampling capacitor having a first terminal coupled to the first input port and having a second terminal coupled to the second input port;
- and
- a metal-oxide-semiconductor capacitor having source-drain terminals coupled to the first input port and a gate terminal configured to receive a control signal.
A method of operating an image sensor, comprising:
- reading a signal from an image sensor pixel;
- conveying the signal through a column line;
- with a data converter, receiving the signal from the column line;
- with the data converter, activating a metal-oxide-semiconductor capacitor;
- and
- with the data converter, sampling the received signal while the metal-oxide-semiconductor capacitor is activated.
A data converter, comprising:
- an input port;
- a comparator having an input coupled to the input port;
- a digital-to-analog converter coupled to the input of the comparator;
- and
- a metal-oxide-semiconductor capacitor having source-drain terminals coupled to the input port and having a gate terminal configured to receive a control signal that is asserted during a charge sampling phase and that is subsequently deasserted to provide a voltage gain.
Dependencies are inferred from the claim text.