Method and apparatus for time-differential comparison of an analog signal
First Claim
1. A time-differential analog comparator, comprising:
- a variable frequency signal source coupled to provide a repeating signal having a plurality of periods, wherein each period has a frequency corresponding to a value of an analog input;
a counting circuit coupled to count the periods of the repeating signal, wherein the counting circuit is coupled to count in a first direction for a first time interval and coupled to count in a second direction opposite to the first direction for a second time interval that occurs after an end of the first time interval, wherein the counting circuit outputs a digital count signal; and
an evaluation circuit coupled to the counting circuit to generate a decision signal in response to a count of the periods of the repeating signal indicated by the digital count signal after an end of the second time interval, wherein the first time interval is not equal to the second time interval to generate an offset in the decision signal.
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Abstract
A time-differential analog comparator is disclosed. An example apparatus according to aspects of the present invention includes a source of a variable frequency signal having a frequency responsive to an analog input. A counting circuit is coupled to count cycles of the variable frequency signal. The counting circuit is coupled to count in a first direction for a first time interval and is coupled to count in a second direction opposite to the first direction for a second time interval that occurs after an end of the first time interval. The counting circuit outputs a digital count signal and an evaluation circuit is coupled to generate a decision signal in response to the digital count signal after an end of the second time interval. The first time interval is not equal to the second time interval to generate an offset in the decision signal.
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Citations
15 Claims
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1. A time-differential analog comparator, comprising:
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a variable frequency signal source coupled to provide a repeating signal having a plurality of periods, wherein each period has a frequency corresponding to a value of an analog input; a counting circuit coupled to count the periods of the repeating signal, wherein the counting circuit is coupled to count in a first direction for a first time interval and coupled to count in a second direction opposite to the first direction for a second time interval that occurs after an end of the first time interval, wherein the counting circuit outputs a digital count signal; and an evaluation circuit coupled to the counting circuit to generate a decision signal in response to a count of the periods of the repeating signal indicated by the digital count signal after an end of the second time interval, wherein the first time interval is not equal to the second time interval to generate an offset in the decision signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of performing a time-differential comparison of an analog signal, comprising:
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generating a repeating signal having a plurality of periods, wherein each period has a frequency corresponding to a value of the analog signal; counting in a first direction during a first time interval in response to the periods of the repeating signal; counting in a second direction during a second time interval in response to the periods of the repeating signal; generating a digital count signal representative of the count of periods after the second time interval; and generating a decision signal in response to the digital count signal, wherein the first time interval is not equal to the second time interval to generate an offset in the decision signal. - View Dependent Claims (12, 13, 14, 15)
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Specification