Fingerprint sensor

Abstract

The invention, which relates to the integrated circuit field, discloses a fingerprint sensor comprising a dielectric layer, an excitation signal generator, a control switch, an acquisition unit, a control circuit, a selection switch, a programmable amplifier and an analog-to-digital converter. The dielectric layer covers the surfaces of the acquisition unit; wherein the excitation signal generatoris connected with the acquisition unit through the control switch, the acquisition unit is sequentially connected with the programmable amplifier and the analog-to-digital converter through the selection switch and converts output voltage into digital signals, and the control circuit provides time sequence signals and control signals for the selection switch, the programmable amplifier and the analog-to-digital converter. On the premise of ensuring robustness, direct contact between fingers of a human body and electric signals is avoided, the use comfort is improved, and meanwhile the packaging cost of the fingerprint sensor and the installation difficulty when the fingerprint sensor is embedded into a whole machine are reduced.

Description

technical field [0001] The invention relates to the field of integrated circuits, in particular to a fingerprint sensor without an external excitation ring. Background technique [0002] According to the different principles of fingerprint sensors to collect fingerprint images, fingerprint sensors can be roughly divided into optical fingerprint sensors, semiconductor capacitive fingerprint sensors and ultrasonic fingerprint sensors. [0003] In order to improve the sensitivity, collection speed and anti-static ability of the fingerprint sensor, people have developed an active fingerprint sensor. The active fingerprint sensor mainly generates an excitation signal with a certain timing requirement inside the chip. When the finger touches the metal ring, the excitation signal is transmitted to the finger to be collected through the chip PAD, the binding wire and the metal ring installed around the sensor. The finger equivalent capacitance formed between the finger surface and ...

AI Technical Summary

Problems solved by technology

However, the introduction of an external excitation ring increases the cost of chip packaging and the difficulty of installing the chip on the whole machine. The casing of the whole machine is usually grounded, and the excitation ring of the fingerprint sensor needs to be insulated from the casing of the whole machine. no direct contact

In addition, for different groups of people, in order to obtain good robustness, the excitation signal is often designed as an electrical signal with high current and strong driving force. For some sensitive groups, when the finger directly touches the excitation ring, it will often bring some Tingling sensation, which reduces the comfort of using the product

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