Charge transfer circuit for capacitive sensing and apparatus for detecting fingerprint having thereof

A fingerprint recognition device comprising:

• a charge transfer circuit for capacitive sensing;
• and
• a bezel;
• wherein the charge transfer circuit comprises:
• a variable capacitor defined through a sensor plate connected to one end of a drive line and one end of an X-drive line;
• an X-drive part disposed between a voltage input terminal and another end of the X-drive line opposing the variable capacitor;
• a buffer circuit unit in which an inverting input terminal and an output terminal of an operational amplifier are connected to each other;
• an active output voltage feedback unit comprising the buffer circuit unit and disposed between a voltage output terminal and another end of the drive line of which the one end is connected to the variable capacitor;
• and
• a shielding plate disposed under the sensor plate to block a noise generated by a circuit under the sensor plate,
• wherein one end of the shielding plate is connected to an output terminal of the active output voltage feedback unit to which an output terminal of the buffer circuit unit is connected in order to remove a parasitic capacitor generated between the sensor plate and the shielding plate,
• wherein the output terminal of the active output voltage feedback unit opposing the one end of the drive line is connected to the other end of the drive line,
• wherein one end of the bezel is connected to the one end of the X-drive line and another end of the bezel is directly contactable by a finger.

A fingerprint recognition device comprising:

• a charge transfer circuit for capacitive sensing;
• and
• a top metal,
• wherein the charge transfer circuit comprises:
• a variable capacitor defined through a sensor plate connected to one end of a drive line and one end of an X-drive line;
• an X-drive part disposed between a voltage input terminal and another end of the X-drive line opposing the variable capacitor;
• a switched capacitor integrator disposed between a voltage output terminal and another end of the drive line of which the one end is connected to the variable capacitor;
• and
• a shielding plate connected to a first input terminal of the switched capacitor integrator,
• wherein the first input terminal is connected to the other end of the drive line,
• wherein the top metal is disposed under a passivation layer and connects a finger to the X-drive line through the passivation layer,
• wherein the top metal comprises a Tx plate of which one end is connected to the one end of the X-drive line and of which another end is connected to the passivation layer so as to transfer a driving signal of the X-drive line to the finger through the passivation layer,
• wherein the Tx plate is spaced apart from the sensor plate by a predetermined distance.

A fingerprint recognition device comprising:

• a charge transfer circuit for capacitive sensing;
• and
• a top metal,
• wherein the charge transfer circuit comprises:
• a variable capacitor defined through a sensor plate connected to one end of a drive line and one end of an X-drive line;
• an X-drive part disposed between a voltage input terminal and another end of the X-drive line opposing the variable capacitor;
• a buffer circuit unit in which an inverting input terminal and an output terminal of an operational amplifier are connected to each other;
• an active output voltage feedback unit comprising the buffer circuit unit and disposed between a voltage output terminal and another end of the drive line of which the one end is connected to the variable capacitor;
• and
• a shielding plate connected to an output terminal of the active output voltage feedback unit,
• wherein the output terminal of the active output voltage feedback unit opposing the one end of the drive line is connected to the other end of the drive line,
• wherein the top metal is disposed under a passivation layer and connects a finger to the X-drive line through the passivation layer,
• wherein the top metal comprises a Tx plate of which one end is connected to the one end of the X-drive line and of which another end is connected to the passivation layer so as to transfer a driving signal of the X-drive line to the finger through the passivation layer,
• wherein the Tx plate is spaced apart from the sensor plate by a predetermined distance.