Patent ID: 7898453

Claim:
An analog-to-digital converter comprising: a comparator comprising a comparator input and a comparator output; a control block comprising a control block input coupled to the comparator output; a plurality of pairs of capacitors, capacitance values of the pairs of capacitors forming a substantially binary progression, each pair of capacitors of the plurality of pairs of capacitors comprising a first capacitor and a second capacitor, each capacitor of the plurality of pairs of capacitors comprising a first end coupled to the comparator input and a second end; and a sampling switch comprising a switch input configured to receive an input voltage, a switch output coupled to the comparator input, and a control switch input, the sampling switch being configured to be closed and transmit the input voltage to the switch output, or to be open and to isolate the input voltage from the switch output, depending on state of the control switch input; wherein the control block is configured to: provide an initial bias to the plurality of pairs of capacitors so that the second ends of the first capacitors are coupled to a first reference voltage, and the second ends of the second capacitors are coupled to a second reference voltage, the second reference voltage being less than the first reference voltage, close and open the sampling switch to charge the first and second capacitors so that a voltage Vs at the comparator input is substantially equal to the input voltage at the time the sampling switch is opened, cause the comparator to compare the voltage Vs to a predetermined comparator threshold Vt to obtain a first bit of an output word corresponding to a digital representation of the voltage Vs, and for said each pair of capacitors in sequence of decreasing capacitance values, (1) if last obtained bit of the word indicated that the voltage Vs is greater than the predetermined comparator threshold Vt (Vs>Vt), toggle from a first reference voltage to a second reference voltage the second end of the first capacitor of said each pair of capacitors in sequence, or, if the last obtained bit of the word indicated that Vt>Vs, toggle from the second reference voltage to the first reference voltage the second end of the second capacitor of said each pair of capacitors in sequence, and (2) after toggling, cause the comparator to compare the voltage Vs to the predetermined comparator threshold Vt to obtain a following bit of the word.