Capacitive fingerprint sensor
A fingerprint sensor and capacitive technology, applied in the direction of acquiring/arranging fingerprints/palmprints, instruments, electrical components, etc., can solve the problems that the integrator is easy to reach saturation, the output dynamic range of the fingerprint sensor is small, and the effective signal is small.
Active Publication Date: 2017-05-10
SHENZHEN GOODIX TECH CO LTD
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Problems solved by technology
[0005] However, for an integral semiconductor capacitive fingerprint sensor, it usually includes an integrator, the capacitance of the substrate in the fingerprint capacitor, the capacitance from the metal layer closest to the fingerprint to the system ground, that is, the parasitic capacitance will produce a very large output at the integrator output. Large base signal, the size of the base signal is about 100 times of the effective signal corresponding to the fingerprint capacitor. After the amplifier is amplified, the base signal is much larger than the effective signal, resulting in a smaller effective signal; at the same time, the base signal is amplified so that The integrator is easy to reach saturation, resulting in a small output dynamic range of the fingerprint sensor
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[0018] The implementation of the present application will be described in detail below in conjunction with the drawings and examples, so that the realization process of how the present application uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.
[0019] The following will further schematically explain the present invention.
[0020] figure 1 It is a schematic diagram of the circuit structure of a typical fingerprint sensor; figure 1 As shown, the fingerprint sensor includes an integrating capacitor C i , switch S 1 -S 4 , Amplifier 100. where the switch S 1 and S 3 The switch state is divided by the first clock signal ck 1 control, switch S 2 and S 4 The switching state is affected by the second clock signal ck 2 control, the first clock signal ck 1 with the second clock signal ck 2 Can be two non-overlapping clock signals respectively.
[0021] During the integration phase, the fi...
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An embodiment of the present invention provides a capacitive fingerprint sensor comprising an integrator, a flip-flop, and a substrate canceling circuit, the integrator stores an electric charge from a fingerprint capacitor to generate an output signal and to transmit to the flip-flop, the flip-hop is used for triggering the substrate canceling circuit to generate a substrate canceling signal when the output signal exceeds a set threshold and outputting the signal to the integrator, and the substrate canceling signal adjusts an output signal of the integrator to the set threshold, avoiding the need for saturation of the integrator, thereby increasing the dynamic range of the integrator.
Description
technical field [0001] Embodiments of the present invention relate to the technical field of biological feature identification, and in particular to a capacitive fingerprint sensor. Background technique [0002] Since the fingerprint has lifelong invariance, uniqueness and convenience, it can provide a higher level of identity security authentication. When performing identity security authentication, a fingerprint sensor (Fingerprint Sensor) is usually used as a device for realizing automatic fingerprint collection. [0003] Fingerprint sensors are mainly divided into optical fingerprint sensors, semiconductor capacitive sensors, semiconductor thermal sensors, semiconductor pressure sensors, ultrasonic sensors and radio frequency (RF) sensors according to the sensing principle. [0004] Taking the semiconductor capacitive fingerprint sensor as an example, on a "flat plate" integrated with tens of thousands of semiconductor devices, a finger is attached to it to form the oth...
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IPC IPC(8): G06K9/00G06V30/144
CPCG06V40/1306H03K17/962
Inventor 张孟文詹昶皮涛李周群
Owner SHENZHEN GOODIX TECH CO LTD