A 39.5-dB SNR, 300-Hz Frame-Rate, 56 × 70-Channel Read-Out IC for Electromagnetic Resonance Touch Panels

Abstract

In this paper, a pen detection analog system for an electromagnetic resonance (EMR) touch panel is presented. An adaptive charge pump is proposed in the transmitter to drive a high current to the EMR panel and achieve a high signal-to-noise ratio (SNR) in the receiver. To compensate for the mismatches between the channels due to fabrication variations of the EMR panels and process variations of the analog front-ends (AFEs), a transmitter driver with an adaptive controller is proposed, and an AFE calibration is implemented in the transmitter and the receiver, respectively. Also, a 9-bit, 2-MS/s time-interleaved flash successive-approximation-register (SAR) analog-to-digital converter (ADC) with 3-bit flash and 6-bit SAR ADCs is proposed to increase the frame rate with small area and power consumption. External noises, such as display and charger noises, can be rejected by the differential processing, analog low-pass filter, and digital filters in the digital signal processor (DSP). This read-out integrated circuit is implemented in a 0.18-μm Bipolar-CMOS-DMOS (BCD), and the die area is ${\text{40 mm}}^{\text{2}}$ including DSP and ADCs. The power consumptions are 110 and 45 mW in the transmitter and receiver modes, respectively. The SNR is about 39.5 dB and the frame rate is about 300 Hz in the 56 × 70 touch panel.