A low-power capacitance detection device for fingerprint identification

Abstract

The invention discloses a low-power capacitance detection apparatus used for fingerprint identification. The apparatus comprises a first oscillator, a second oscillator, a capacitance detection moduleand a register configuration module, wherein the first oscillator and the second oscillator have same parameter configuration; the capacitance detection module comprises a first shift register and asecond shift register; a first output end of the first oscillator is connected with a control port of the first shift register; a second output end of the first oscillator is connected with a controlport of the second shift register; a collection port of the second oscillator collects a finger capacitance signal; and an output port of the second oscillator is connected with a data port of the first shift register and a data port of the second shift register. Whether finger pressing exists or not is judged by adopting a register chain instead of an original counter, so that the power consumption is reduced.

Description

technical field [0001] The invention relates to the field of fingerprint identification, in particular to a low power consumption capacitance detection device for fingerprint identification. Background technique [0002] With the rapid development of biometric technology, fingerprint recognition, as one of the oldest biometric technologies, has entered everyone's daily life. In addition, the semiconductor industry is changing with each passing day, and fingerprint sensors are gradually developing towards miniaturization and low cost following the "More than moore" law of the semiconductor industry. In portable devices such as mobile phones, Pads, and smart bracelets, fingerprint recognition accounts for almost 80% of the share, which greatly facilitates the daily encryption operations of portable devices and becomes an indispensable part of our work and life. [0003] Fingerprint sensor (also known as fingerprint sensor) is a key device to realize automatic fingerprint coll...

AI Technical Summary

Problems solved by technology

With the gradual maturity of fingerprint technology, its various characteristics and specifications will become higher and higher. In this capacitance detection device, the problem of huge register flipping power consumption caused by the long-term operation of the counter has to be paid attention to.

First, the flip-flop and logic gate flip-flop frequency of the traditional capacitance detection device is high because the counter is always in the working state

At the same time, if the system clock is used for single-frequency sampling, the anti-interference ability of the circuit is weak. Therefore, it is necessary to use two clock sources and two counters for comparison operations to improve the anti-interference ability. These problems will cause great power consumption.

Second, the traditional capacitance detection has poor configurability because the main components of the work are in the analog part, while the digital part is only for counting and comparison.

Once the environmental factors of the chip change, non-finger and other objects will also be detected, and the false recognition rate is high

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