US 10,074,004 B2Granted

Capacitive fingerprint sensor with integrator

AssigneeMicroarray Microelectronics Corp., Ltd

InventorsKefeng Xu, Yangyuan Li

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Abstract

The present invention provides a “C-Q-T” type capacitive fingerprint sensor with an integrator. The integrator comprises an amplifier, an integrating capacitor, a reference voltage and a reset circuit. By applying the present invention, linearity and sensitivity of the “C-Q-T” type capacitive fingerprint sensor are improved. During a conversion process of the “C-Q-T”, through introduction of the integrator, charge transfer quantities between a target capacitor and the integrating capacitor can be consistent for each time, so that a sensing equation is optimized, and better linearity is shown in the conversion process. As influence of a background capacitor and of a bus parasitic capacitor on the sensing equation is removed, the sensitivity of the “C-Q-T” type capacitive fingerprint sensor is improved.

Claims12

Dependent claims

A capacitive fingerprint sensor with an integrator, comprising:

a sensing array, a bus, the integrator and a comparison circuit, wherein:
the sensing array comprises a plurality of sensing units, wherein each sensing unit comprises a target electrode, a sensing electrode, a driving electrode, a first level driver, a second level driver, a line selection switch, an initialization switch and a first reference voltage, and an output terminal of each sensing unit is connected to the bus;
the bus is connected to output terminals of the plurality of sensing units and an input terminal of the integrator;
the input terminal of the integrator is connected to the bus, and an output terminal of the integrator is connected to an input terminal of the comparison circuit;
and
the input terminal of the comparison circuit is connected to the output terminal of the integrator, and the output terminal of the comparison circuit is connected to an output terminal of the capacitive fingerprint sensor;
wherein the integrator comprises:
a second reference voltage;
an amplifier;
a second reset switch, wherein a first port of the second reset switch is directly connected to the second reference voltage, and a second port of the second reset switch is directly connected to a first input terminal of the amplifier;
wherein charge quantities of discharge of the integrating capacitor for each time are the same so that a change curve of the charge quantities in the integrating capacitor is linear;
wherein an output voltage of the integrator increases or decreases linearly through time.

9 more elements

A capacitive fingerprint sensor with an integrator, comprising:

a sensing array, a bus, the integrator and a comparison circuit, wherein:
the sensing array comprises a plurality of sensing units, wherein each sensing unit comprises a target electrode, a sensing electrode, a driving electrode, a first level driver, a second level driver, a line selection switch, an initialization switch and a first reference voltage, and an output terminal of each sensing unit is connected to the bus;
the bus is connected to output terminals of the plurality of sensing units and an input terminal of the integrator;
the input terminal of the integrator is connected to the bus, and an output terminal of the integrator is connected to an input terminal of the comparison circuit;
and
the input terminal of the comparison circuit is connected to the output terminal of the integrator, and the output terminal of the comparison circuit is connected to an output terminal of the capacitive fingerprint sensor;
wherein the integrator comprises:
a second reference voltage;
an amplifier, wherein a first input terminal of the amplifier is directly connected to the input terminal of the integrator, a second input terminal of the amplifier is directly connected to the second reference voltage, and an output terminal of the amplifier is directly connected to the output terminal of the integrator;
an integrating capacitor, wherein a first port of the integrating capacitor is directly connected to the first input terminal of the amplifier, and a second port of the integrating capacitor is connected to the output terminal of the amplifier;
and
a second reset switch, wherein a first port of the second reset switch is directly connected to the second reference voltage, and a second port of the second reset switch is directly connected to the first input terminal of the amplifier;
wherein charge quantities of discharge of the integrating capacitor for each time are the same so that a change curve of the charge quantities in the integrating capacitor is linear.

10 more elements

Dependencies are inferred from the claim text.

Facts

Application: 15/230,368Filed 5 Aug 2016
Priority: CN 2015 1 03092228 Jun 2015
Published: US 2017/0235993 A117 Aug 2017
Granted: 11 Sep 2018
Term ends: Not estimatedThe source records don’t support an estimate.

Classification5 codes

G06V 40/1306
Sensors therefor: non-optical, e.g. ultrasonic or capacitive sensing
G06F 3/04166
Control or interface arrangements specially adapted for digitisers: details of scanning methods, e.g. sampling time, grouping of sub areas or time…
G06F 3/0445
By capacitive means: using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
G06V
Image and video recognition