Single-ended amplifier-based touch readout circuit with immunity to display noise

Abstract

To suppress errors in a touch readout circuit due to display noise, differential sensing using fully differential amplifiers is widely used. However, conventional differential sensing methods require additional circuits or increase circuit complexity, thus increasing power consumption and circuit area or requiring additional dummy RX line on the touch panel. In this study, we propose a compact touch readout circuit composed of a single-ended amplifier while keeping the display noise suppression of differential sensing so as to minimize power consumption and circuit area increase and avoid the need for additional dummy RX line. The proposed touch readout circuit for is fabricated in circuit area of 0.4 mm2 with 0.35 µm 3.3 V CMOS process and measured for 10.1-inch touch panel on top of a TFT-LCD panel. With the proposed touch readout circuit, the signal-to-noise ratio (SNR) is improved by up to 13.1 dB compared to the conventional touch readout circuit using single-ended amplifiers.

Keywords

• Readout circuit
• mutual capacitive touch
• display noise suppression
• LC
• OLED
• equipment