The Design of 13 bits ΣΔ ADC for a mutual-capacitance large touch screen controller

Touch sensing circuits for large touch screens require high resolution ADCs with high data rate for accurate and fast touch detection. This paper presents a third-order Sigma Delta ADC design with an input bandwidth of 480 KHz at 61.44 MHz sampling frequency, the SNR and ENOB are measured to be 85 dB and 13 bits respectively. We present an efficient mixed signal design methodology consisting of circuit design, integration, and verification with analog and digital simulations. Using the proposed design methodology, the target Sigma Delta ADC design is implemented with Dongbu 0.18-mu m BDCMOS technology. The design results show its suitability for large mutual-capacitance touch screen controller applications.