High signal to noise ratio capacitive sensing analog front-end

A method for sensing capacitance, comprising:

• generating a signal representative of a capacitance to be sensed;
• converting the generated signal to a sensed voltage representative of the capacitance;
• repeating the generating and the converting during an accumulation period of NA sensing cycles and accumulating the sensed voltages to provide an accumulated analog value;
• amplifying the accumulated analog value;
• and
• converting the amplified accumulated analog value to a digital value representative of the capacitance to be sensed.

A capacitance sensing circuit comprising:

• a capacitance-to-voltage converter configured to receive a signal from a capacitance of a touch screen and to provide an output signal representative of the capacitance;
• a rectification circuit configured to convert the output signal of the capacitance-to-voltage converter to a sensed voltage representative of the capacitance;
• an analog accumulator/filter configured to accumulate sensed voltages during an accumulation period of NA sensing cycles and to filter the sensed voltages, wherein the analog accumulator/filter provides an accumulated analog value;
• an amplifier configured to amplify the accumulated analog value;
• and
• an analog-to-digital converter configured to convert the amplified accumulated analog value to a digital value representative of the capacitance to be sensed.