Nano-power capacitance-to-digital converter

A capacitance-to-digital converter (CDC) comprising:

• a comparator having a first input coupled to a first sensing electrode and a second input coupled to a second sensing electrode;
• a first capacitive digital-to-analog converter (DAC) coupled to the first input of the comparator, the capacitive DAC for applying a first signal to the first sensing electrode;
• a second capacitive digital-to-analog converter (DAC) coupled to the second input of the comparator, the capacitive DAC for applying a second signal to the second sensing electrode;
• and
• a counter for providing control signals to the first and second capacitive DACs, the counter receiving logic signals from a logic unit coupled to an output of the comparator,
• wherein a first counter value corresponding to the control signal provided to the first capacitive DAC from a first counter output and a second counter value corresponding to the control signal provided to the second capacitive DAC from a second counter output are in response to a capacitance on at least the first sensing electrode coupled to the first input of the comparator, and
• wherein the logic unit comprises:
• a first inverter coupled between a first output of the comparator and a first input of an OR gate,
• a second inverter coupled between a second output of the comparator and a second input of the OR gate, and
• a D flip-flop (F/F) coupled to the first input of the OR gate and the output of the OR gate, the D F/F for providing increment or decrement signals to the counter.