FINGERPRINT SENSOR

摘要

The present disclosure provides a fingerprint sensor that comprises a first reference capacitor, a second reference capacitor, a first capacitor and a second capacitor. A first reference voltage is established across the first reference capacitor. The first reference voltage is a function of a capacitance detected in response to a touch event, a first reference capacitance of the first reference capacitor and a stray capacitance. The second reference capacitor has a first end and a second end, and is being configured to maintain a voltage difference between the first end and the second end, the voltage difference being a function of the first reference voltage. The first capacitor has a first capacitance and is coupled to the first end of the second reference capacitor. The second capacitor has a second capacitance and is selectively coupled in parallel with the first capacitor. The ratio of the stray capacitance to the first reference capacitance equals the ratio of the second capacitance to the first capacitance.

主权项

1. A fingerprint sensor, comprising:
a sensing circuit including:
a sensing electrode to detect a capacitance in response to a touch event; anda first reference capacitor across which a first reference voltage is established, the first reference voltage being a function of the capacitance, a first reference capacitance of the first reference capacitor and a stray capacitance; and a cancellation circuit selectively coupled to the sensing circuit, the cancellation circuit including:
a second reference capacitor across which a second reference voltage is established and between a first end and a second end of which a voltage difference equal to the second reference voltage is maintained, the second reference voltage being a function of the first reference voltage;a first capacitor coupled to the second reference capacitor; anda second capacitor selectively coupled in parallel with the first capacitor and configured to, in conjunction with the first capacitor, distinguish a voltage level at the second end of the second reference capacitor in response to a finger valley contact from a voltage level in response to a finger ridge contact at the second end of the second reference capacitor in the touch event.