PROJECT TITLE :
On-Chip Touch Sensor Readout Circuit Using Passive Sigma-Delta Modulator Capacitance-to-Digital Converter
This paper describes a capacitive type touch sensor readout circuit using passive sigma-delta modulator-primarily based capacitance-to-digital converter. With the proposed approach, the panel condition (touched or untouched) can be effectively converted into the digital level using the panel capacitance because the summing element of the primary-order passive sigma-delta modulator. Similarly, the proposed touch sensor readout circuit does not require an analog-to-digital converter, since the digital format resembling the touch panel condition will be merely obtained by counting the quantity of modulator output pulses inside the detection period. This together with the passive architecture results in a compact and low-power on-chip touch sensor readout circuitry. Furthermore, thanks to the noise shaping property of the sigma-delta modulator, a comparable SNR and detection time with respect to different touch sensor readout circuits can be achieved. The proposed bit sensor readout circuit is implemented using CMOS 0.35- $mu textm$ technology with core space of zero.1 mm $^2$ . The operation of the sensor readout circuit is verified with a $10.4^prime prime $ projective capacitance sort bit panel, where the measured SNR is thirty one.4 dB with power consumption of $65~mu textW$ .
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