A 1 mm Pitch <inline-formula><tex-math notation="LaTeX">$80 \times 80$</tex-math></inline-formula> Channel 322 Hz Frame-Rate Multitouch Distribution Sensor With Two-Step Dual-Mode Capacitance Scan

Abstract

A 1 mm pitch $80 \times 80$ channel 322 Hz frame-rate capacitive multitouch distribution sensor has been developed. High-resolution multiple touch points are detected including touch-strength distribution around them. A two-step dual-mode capacitance scan scheme is proposed, where self- and mutual-capacitance measurements are hierarchically performed in two steps to increase the frame scan rate that is otherwise reduced due to high resolution. 160 row-and-column dedicated parallel ADCs further increase the scan rate. A time-domain counter-based slope ADC suppresses power and area penalty for the parallel ADC approach. A signal attenuation due to the sensor capacitance reduction in the high resolution is compensated by thorough noise-reduction techniques in the sensor analog frontend (AFE). A prototype in $0.35\; \upmu \text{m}$ CMOS demonstrates 41 dB signal-to-noise ratio (SNR) with ${>} 5 \times $ tighter sensor-channel pitch, ${>} 10 \times $ faster touch-point scan, ${>} 10 \times $ and ${>} 4 \times $ higher energy and area efficiency to the state-of-the-art touch distribution sensors.