A/D conversion using a variable offset comparator
AssigneeIntel Corporation
InventorsBryan K. Casper, Aaron K. Martin
Life of this patent
Estimating the term…
Abstract
An A/D conversion reference level is applied to an input of a variable offset comparator (i.e. VOC). A binary number that corresponds to the A/D conversion reference level is determined by changing a binary variable that is applied to vary the offset of the VOC until the VOC output changes states. The same procedure is applied to determine corresponding reference, binary numbers for all of the other A/D conversion reference levels. A successive approximation procedure (binary search) is then performed for a reference window in which an input analog level (to be converted into digital form) would fall, by successively applying the reference binary numbers to vary the VOC offset.
Claims19
A method for A/D conversion, comprising:
- determining a plurality of binary numbers that correspond to a plurality of reference levels, respectively, by changing a binary variable that is applied to an offset control input of a comparator that has a variable offset, simultaneously with each of the plurality of reference levels being applied to an input of the comparator, until an output of the comparator changes states;
- and
- performing a search for a reference window in which an input analog level would fall, by successively applying some of the determined plurality of binary numbers to the offset control input of the comparator simultaneously with the analog level being applied to the input of the comparator.
An A/D converter comprising:
- a comparator having a variable offset that is controllable via an offset control input, the comparator having an input to receive an input analog level;
- a multiplexer having an output coupled to the comparator input and an input coupled to receive the input analog level;
- a successive approximation control circuit having an input coupled to an output of the comparator and an output coupled to apply some of a plurality of binary numbers, that correspond to a plurality of A/D conversion reference levels, respectively, to the offset control input;
- a reference generator coupled to provide one of the plurality of reference levels to a further input of the multiplexer;
- and
- a reference initialization control circuit having an input coupled to the comparator output and a plurality of outputs coupled to control the multiplexer, the reference generator, and the comparator, to determine the plurality of binary numbers.
An electronic system comprising:
- a printed wiring board on which a parallel bus is formed, an integrated circuit (IC) chip package being operatively installed on the board to communicate using the parallel bus, the package having an IC chip that includes a logic function section and an I/O section, the I/O section being an interface between the logic function section and the bus, the I/O section having a bus receiver in which an equalization loop has an A/D converter therein which includes a comparator that has an input coupled to receive a parallel bus signal, the comparator having a variable offset that is controllable via an offset control input, the I/O section further includes a successive approximation control circuit having an input coupled to an output of the comparator and an output coupled to apply some of a plurality of binary numbers, that correspond to a plurality of A/D converter reference levels, respectively, to the offset control input.
A method for A/D conversion, comprising:
- applying an A/D conversion reference level to a differential input of a variable offset comparator;
- determining an offset code that corresponds to the reference level applied, by changing an offset code variable that is applied to an offset control input of the comparator simultaneously with the reference level being applied to the input of the comparator, until an output of the comparator changes states;
- recording the offset code that caused the comparator output to change states as corresponding to the reference level being applied;
- and
- repeating the previous operations for all other A/D conversion reference levels.
Dependencies are inferred from the claim text.