Patent ID: 8344928

Claim:
A method for converting a capacitance of a sensed capacitive element to a binary sequence, the method comprising, for each binary value of the binary sequence: generating a first clock signal that has a logic value one for a first interval and logic value zero for a second interval in each cycle of the first clock signal; generating an excitation signal that has a first voltage during the first interval of the first clock signal and a second voltage value during the second interval of the first clock; supplying the excitation signal to the sensed capacitive element to accumulate an electrical charge on the capacitive element; generating a second clock signal that has a logic value one for a first interval and logic value zero for a second interval in each cycle of the second clock signal; generating a reference electrical charge dependent upon the current binary value of the binary sequence; integrating a combination of the reference charge and the electrical charge on the capacitive element during the first interval of the second clock to produce an integrated electrical charge; and comparing the integrated electrical charge to a threshold to obtain a next binary value of the binary sequence, the next binary value being dependent upon whether the integrated electrical charge is above or below the threshold, wherein the cycle of the first clock signal has a non-constant duration, and wherein the cycle of the second clock signal has a non-constant duration.