Fingerprint sensing circuit and electrical device

• US 10,289,888 B2
• Filed: 01/03/2017
• Issued: 05/14/2019
• Est. Priority Date: 01/03/2017
• Status: Active Grant

• Current Assignee: Himax Technologies Ltd. (Himax Technologies Incorporated)
• Original Assignee: Himax Technologies Ltd. (Himax Technologies Incorporated)
• Inventors: He, Jia-Ming, Chang, Yaw-Guang
• Primary Examiner(s): Potts, Ryan P
• Application Number:
  US15/397,709
• Publication Number:
  US 20180189537A1
• Time in Patent Office: 861 Days
• Field of Search: None
• CPC Class Codes: G06V 10/955 using specific electronic processors
• CPC Class Codes: G06V 40/1306 non-optical, e.g. ultrasonic or capacitive sensing
• CPC Class Codes: G06V 40/1359 Extracting features related to ridge properties; Determining the fingerprint type, e.g. whorl or loop
• CPC Class Codes: H03K 17/962 Capacitive touch switches
• CPC Class Codes: H03K 17/9622 using a plurality of detectors, e.g. keyboard
• CPC Class Codes: H03K 2217/960725 Charge-transfer
• CPC Class Codes: H03K 2217/960735 characterised by circuit details

Abstract

The fingerprint sensing circuit including sensing electrodes, switches, a sensing line and flip flops. First terminals of the switches are respectively coupled to the sensing electrodes. The sensing line is coupled to second terminals of the switches. Output terminals of the flip flops are respectively coupled to control terminals of the switches. An input terminal of part of the flip flops is coupled to the output terminal of a previous flip flop.

Claims

1. A fingerprint sensing circuit, comprising:

a plurality of sensing electrodes;

a plurality of switches, wherein first terminals of the switches are respectively coupled to the sensing electrodes;

a sensing line, coupled to second terminals of the switches;

a plurality of flip flops, wherein each of the flip flops comprises an output terminal, the output terminals of the flip flops are respectively coupled to control terminals of the switches, and an input terminal of part of the flip flops is coupled to the output terminal of a previous flip flop of the flip flops; and

a plurality of AND gates, wherein first input terminals of the AND gates are coupled to a selection signal, second input terminals of the AND gates are respectively coupled to the output terminals of the flip flops, and output terminals of the AND gates are respectively coupled to the control terminals of the switches.

2. The fingerprint sensing circuit of claim 1, wherein the sensing electrodes are formed in a first conductive layer, and the sensing line is formed in a second conductive layer.

3. The fingerprint sensing circuit of claim 2, further comprising:

a clock signal line formed in the second conductive layer and coupled to trigger terminals of the flip flops.

4. The fingerprint sensing circuit of claim 3, wherein the sensing line and the clock signal line extend along a first direction and parallel with each other.

5. The fingerprint sensing circuit of claim 4, wherein the flip flops are formed in an underlying circuit, and the first conductive layer and the second conductive layer are formed above the underlying circuit.

6. The fingerprint sensing circuit of claim 1, wherein the flip flops comprise:

a first flip flop having an input terminal coupled to a pulse signal; and

a second flip flop having an input terminal coupled to the output terminal of the first flip flop.

7. An electrical device comprising a fingerprint sensing circuit, wherein the fingerprint sensing circuit comprises:

a plurality of sensing electrodes;

a plurality of switches, wherein first terminals of the switches are respectively coupled to the sensing electrodes;

a sensing line, coupled to second terminals of the switches;

a plurality of flip flops, wherein each of the flip flops comprises an output terminal, the output terminals of the flip flops are respectively coupled to control terminals of the switches, and an input terminal of part of the flip flops is coupled to the output terminal of a previous flip flop of the flip flops; and

a plurality of AND gates, wherein first input terminals of the AND gates are coupled to a selection signal, second input terminals of the AND gates are respectively coupled to the output terminals of the flip flops, and output terminals of the AND gates are respectively coupled to the control terminals of the switches.

8. The electrical device of claim 7, wherein the sensing electrodes are formed in a first conductive layer, and the sensing line is formed in a second conductive layer.

9. The electrical device of claim 8, further comprising:

a clock signal line formed in the second conductive layer and coupled to trigger terminals of the flip flops.

10. The electrical device of claim 9, wherein the sensing line and the clock signal line extend along a first direction and parallel with each other.

11. The electrical device of claim 10, wherein the flip flops are formed in an underlying circuit, and the first conductive layer and the second conductive layer are formed above the underlying circuit.

12. The electrical device of claim 7, wherein the flip flops comprise:

a first flip flop having an input terminal coupled to a pulse signal; and

a second flip flop having an input terminal coupled to the output terminal of the first flip flop.