Fingerprint sensing device and method operating the same
First Claim
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1. A fingerprint sensing device, comprising:
- at least one sensing core, having a working power terminal and a working ground terminal, for fetching fingerprint images, wherein the at least one sensing core comprises a plurality of capacitive sensing units;
a system unit, having a system power terminal which is connected to a power supply and a system ground terminal which is connected to ground;
at least one switching unit, connected between the sensing core and the system unit, comprising;
a power switch, connected between the working power terminal and the system power terminal;
a ground switch, connected between the working ground terminal and the system ground terminal;
a drive-up switch, connected between the working ground terminal and the system power terminal; and
a drive-down switch, connected between the working power terminal and the system ground terminal; and
a charge holding unit, electrically connected between the working power terminal and the working ground terminal, for providing power to the sensing core while power is not provided to the sensing core by the system unit,wherein the switching unit switches between the following four operation states;
a normal state, the power switch and the ground switch are both turned on and the rest of the switches are turned off, to provide power from the system unit to the sensing core;
an isolation state, all of the switches in the switching unit are turned off and power is provided to the sensing core by the charge holding unit to prevent glitches from occurring;
a drive-up state, the drive-up switch is turned on and the rest of the switches are turned off, to lift-up the voltage of the sensing core by a voltage level being equal to the voltage difference between the system power terminal and the system ground terminal; and
a drive-down state, the drive-down switch is turned on and the rest of the switches are turned off, to drive-down the voltage of the sensing core by the voltage level being equal to the voltage difference between the system power terminal and the system ground terminal.
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Abstract
A fingerprint sensing device and a method operating the fingerprint sensing device are provided. The fingerprint sensing device includes at least one sensing core, a system unit, at least one switching unit and a charge holding unit. The switching unit is connected between the sensing core and the system unit to provide four different operation states: a normal state; an isolation state; a drive-up state; and a drive-down state. A voltage shift between the finger and the sensing core is generated by controlling the switching unit to perform different operation states in various orders.
10 Citations
24 Claims
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1. A fingerprint sensing device, comprising:
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at least one sensing core, having a working power terminal and a working ground terminal, for fetching fingerprint images, wherein the at least one sensing core comprises a plurality of capacitive sensing units; a system unit, having a system power terminal which is connected to a power supply and a system ground terminal which is connected to ground; at least one switching unit, connected between the sensing core and the system unit, comprising; a power switch, connected between the working power terminal and the system power terminal; a ground switch, connected between the working ground terminal and the system ground terminal; a drive-up switch, connected between the working ground terminal and the system power terminal; and a drive-down switch, connected between the working power terminal and the system ground terminal; and a charge holding unit, electrically connected between the working power terminal and the working ground terminal, for providing power to the sensing core while power is not provided to the sensing core by the system unit, wherein the switching unit switches between the following four operation states; a normal state, the power switch and the ground switch are both turned on and the rest of the switches are turned off, to provide power from the system unit to the sensing core; an isolation state, all of the switches in the switching unit are turned off and power is provided to the sensing core by the charge holding unit to prevent glitches from occurring; a drive-up state, the drive-up switch is turned on and the rest of the switches are turned off, to lift-up the voltage of the sensing core by a voltage level being equal to the voltage difference between the system power terminal and the system ground terminal; and a drive-down state, the drive-down switch is turned on and the rest of the switches are turned off, to drive-down the voltage of the sensing core by the voltage level being equal to the voltage difference between the system power terminal and the system ground terminal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24)
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Specification