Digitally assisted control over comparator input common mode
AssigneeQUALCOMM Incorporated
InventorsLei Sun, Ganesh Kiran, Seyed Arash Mirhaj, Dinesh Jagannath Alladi
Life of this patent
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Abstract
Methods and apparatus for digitally controlling a common-mode voltage of a comparator. An example comparator circuit generally includes a first comparator and a sensing circuit configured to digitally track a common-mode voltage of the first comparator. The comparator circuit may further include a first capacitive array having a common terminal coupled to a first input of the first comparator and selectively coupled to an input of the sensing circuit. The comparator circuit may further include a second capacitive array having a common terminal coupled to a second input of the first comparator and selectively coupled to the input of the sensing circuit.
Claims19
An analog-to-digital converter (ADC) comprising:
- a first comparator having a first input and a second input;
- a second comparator having a first input, a second input, and an output;
- a digital-to-analog converter (DAC) coupled to at least one of the first input or the second input of the first comparator and selectively coupled to the first input of the second comparator;
- a common-mode voltage generator having an output coupled to the second input of the second comparator, wherein the common-mode voltage generator comprises a replica transistor matching an input-stage transistor of the first comparator;
- and
- a processing system having an input coupled to the output of the second comparator and having a set of outputs coupled to the DAC.
A comparator circuit comprising:
- a first comparator;
- and
- a sensing circuit configured to digitally track a common-mode voltage of the first comparator, wherein the sensing circuit comprises:
- a second comparator having a first input, a second input, and an output, wherein an input of the sensing circuit is the first input of the second comparator;
- a common-mode voltage generator having an output coupled to the second input of the second comparator, wherein the common-mode voltage generator comprises a replica transistor matching an input-stage transistor of the first comparator;
- and
- a processing system configured to adjust digital control signals for controlling the common-mode voltage of the first comparator based on the output of the second comparator.
A method for tracking a common-mode voltage of a first comparator, comprising:
- sampling the common-mode voltage of the first comparator, based on a common-mode input voltage and a reference voltage, across input terminals of the first comparator;
- generating a target common-mode voltage with a common-mode voltage generator comprising a replica transistor that matches an input-stage transistor of the first comparator;
- comparing, using a second comparator, the sampled common-mode voltage to the target common-mode voltage;
- and
- adjusting control signals applied to a digital-to-analog converter (DAC) coupled to one of the input terminals of the first comparator according to the comparison between the sampled common-mode voltage and the target common-mode voltage.
Dependencies are inferred from the claim text.