Cell structure and operation method for fingerprint sensor employing pseudo-direct scheme

A fingerprint sensor comprising:

• a sensor plate comprising a plurality of cells;
• a driving signal generation unit disposed between an external voltage input terminal and the sensor plate to generate a driving signal;
• an active output voltage feedback unit disposed between one end of a variable capacitor and a voltage output terminal;
• and
• a shielding plate provided below the sensor plate and connected to an output terminal of the active output voltage feedback unit to block a noise generated from a circuit disposed below the sensor plate,
• wherein the fingerprint sensor further comprises:
• a driving signal control switch having one end connected to the driving signal generation unit and the other end connected to the sensor plate to set at least a portion of the plurality of cells of the sensor plate as a sensing cell and at least a portion of cells, which are spaced by a predetermined area from the set sensing cells, as a driving cell;
• and
• an isolation cell control switch having one end connected to the driving signal control switch and the other end connected to the ground to set cells in a predetermined area, in which the sensing cell and the driving cell are spaced apart from each other, as an isolation cell,
• wherein the sensing cell measures a capacitance formed between a finger and the sensing plate, the driving cell provides a driving signal generated from the driving signal generation unit to the finger, and the isolation cell is connected to the ground to remove a capacitance directly applied from the driving cell to the sensing cell.

A method for sensing a fingerprint, the method comprising:

• setting at least a portion of a plurality of cells of a sensor plate as a sensing cell configured to measure a capacitance formed between a finger and the sensing plate;
• setting at least a portion of cells around the set sensing cells of the plurality of cells of the sensor plate as a driving cell configured to provide a driving signal to a finger;
• providing a driving signal from the driving cell to the finger;
• and
• outputting a sensing signal by integrating a capacitance detected in the sensing cell by the signal applied from the driving cell to the finger.

A method for sensing a fingerprint, the method comprising:

• setting at least a portion of a plurality of cells of a sensor plate as a sensing cell configured to measure a capacitance formed between a finger and the sensing plate;
• setting at least a portion of cells spaced by a predetermined area from the set sensing cells as a driving cell configured to provide a driving signal to a finger;
• setting cells in a predetermined area in which the sensing cell and the driving cell are spaced apart from each other as an isolation cell;
• providing a driving signal to the driving cell;
• and
• outputting a sensing signal by integrating a capacitance detected in the sensing cell by the signal applied from the driving cell to the finger.