Capacitive Fingerprint Sensor for Contactless Payment Cards
Thomas Suwald, Thomas Rottschafer · 2019
This paper examines requirements and solutions for a low-power, low-noise, and low-cost capacitive fingerprint sensor specifically for contactless payment cards. A first prototype chip realized in a 1.4 μm CMOS process comprises 96 x 96 sensing elements at a resolution of 254 dpi, has a die area of 9.8 x 10.6 mm2and consumes 1.9mA at 2.5V. The single-sense-amplifier design avoids a bezel and has an embedded ESD-protection down to pixel cell level. A new oversampling method is proposed that enhances the sensitivity and effectively attenuates sampling errors caused by quantization and settling without compromising the sample-rate.