Capacitive fingerprint sensor

A capacitive fingerprint sensor, comprising:

• a sensor ground generator, a sensing unit, a charge accumulation unit and a comparison circuit, wherein the sensor ground generator comprises a power supply circuit, a fifth switch and a sixth switch;
• the power supply circuit has an input end connected with an input power supply (VIN), and an output end connected with a first port of the fifth switch;
• the fifth switch has the first port connected with the output end of the power supply circuit, and a second port connected with an output end (SGND) of the sensor ground generator;
• and
• the sixth switch has a first port connected with the output end (SGND) of the sensor ground generator, and a second port connected with a ground level (GND).

An operating method of a capacitive fingerprint sensor, wherein the capacitive fingerprint sensor is operated according to the following time sequence:

• step 1, resetting a charge accumulation unit;
• step 2, setting a first level control signal to high;
• step 3, closing an initialization switch;
• step 4, enabling a ground end SGND of the fingerprint sensor to output a ground level;
• step 5, setting the first level control signal to low;
• step 6, opening the initialization switch;
• step 7, enabling the ground end SGND of the fingerprint sensor to output a high-voltage level;
• step 8, closing a row selection switch;
• step 9, opening the row selection switch;
• and
• step 10, returning to step 2.