Patent ID: 8188902

Claim:
An apparatus comprising: a capacitive digital-to-analog converter (CDAC) having a resolution of N-bits that receives an analog input signal and a reference voltage; a first comparator stage having: a first comparator having a first input terminal, a second input terminal, and an output terminal, wherein the first input terminal of the first comparator is coupled to the CDAC, and wherein the second terminal of the first comparator receives a first offset voltage; and a second comparator having a first input terminal, a second input terminal, and an output terminal, wherein the first input terminal of the second comparator is coupled to the CDAC, and wherein the second terminal of the second comparator receives the first offset voltage; a plurality of second comparator stages coupled in series with one another in a sequence, wherein each second comparator stage has: an amplifier that is coupled to one of the CDAC and the amplifier from the previous second comparator stage of the sequence; a third comparator having a first input terminal, a second input terminal, and an output terminal, wherein the first input terminal of the third comparator is coupled to the amplifier, and wherein the second terminal of the third comparator receives at least one of a plurality of second offset voltages; and a fourth comparator having a first input terminal, a second input terminal, and an output terminal, wherein the first input terminal of the fourth comparator is coupled to the amplifier, and wherein the second terminal of the fourth comparator receives at least one of a plurality of second offset voltages; and successive approximation register (SAR) logic that is coupled to the output terminals of the first and second comparator from the first comparator stage, the output terminals of the third and fourth comparators from each of the second comparator stages, and the CDAC, wherein the SAR logic controls the CDAC, and wherein the SAR logic performs a successive approximation ternary search using the output values from the first comparator, the second comparator, each third comparator, and each fourth comparator.