Electrostatic discharge protection of a capacitive type fingerprint sensing array

Distance measuring apparatus for providing an output indicative of the ridge/valley fingerprint pattern of a fingertip, said apparatus comprising:

• a physical array having a plurality of individual distance-sensing capacitance-cells;
• each capacitance-cell including a first and a second electrically ungrounded capacitor plate that are electrically isolated from each other and are placed below an ungrounded dielectric surface that is adapted for physical association with a portion of an electrically ungrounded fingertip;
• each capacitance-cell including an amplifier having an electrically ungrounded input-node connected to said first capacitor plate, and having an electrically ungrounded output-node connected to said second capacitor plate;
• said first and said second of capacitor plates being adapted to form a compound-capacitor with an ungrounded fingertip currently resident on said dielectric surface, said compound-capacitor providing amplifier feedback as a function of a distance between a portion of the ungrounded fingertip ridge/valley pattern and said dielectric surface;
• and
• electrically grounded metal path means placed below said ungrounded dielectric surface in a manner to be electrically isolated from, and in a manner to physically surround, each of said capacitor plates of each of said capacitance-cells.

Distance measuring apparatus for providing an output indicative of the ridge/valley fingerprint pattern of a fingertip, said apparatus comprising:

• a physical array having a plurality of individual distance-sensing capacitance-cells;
• each capacitance-cell including ungrounded capacitor plate means placed below an ungrounded dielectric surface that is adapted for physical association with a portion of an electrically ungrounded fingertip;
• each capacitance-cell including an amplifier having an ungrounded input-node and an ungrounded output-node that are connected to said capacitor plate means;
• said capacitor plate means being adapted to form a compound-capacitor with an ungrounded fingertip currently resident on said dielectric surface, said compound-capacitor providing amplifier output-node-to-input-node feedback as a function of a distance between a portion of the ungrounded fingertip ridge/valley pattern and said dielectric surface;
• and
• electrically grounded metal path means placed below said ungrounded dielectric surface in a manner to be electrically isolated from said capacitor plate means of each of said capacitance-cells.

Apparatus providing an electrical output that is indicative of the ridge/valley fingerprint pattern of a fingertip, said apparatus comprising:

• a physical array having a dielectric layer with plurality of individual capacitance-cells formed therein;
• each capacitance-cell including a first and a second electrically ungrounded capacitor plate that are electrically isolated from each other and are placed below an ungrounded dielectric surface of said dielectric layer;
• said dielectric surface being adapted for physical association with an electrically ungrounded fingertip;
• an amplifier for each of said capacitance-cells,
• each of said amplifiers having an electrically ungrounded input-node connected to a said first capacitor plate, and having an electrically ungrounded output-node connected to a said second capacitor plate;
• said first and said second of capacitor plates of each capacitor-cell forming a compound-capacitor with an ungrounded fingertip resident on said dielectric surface;
• said compound-capacitors providing output-to-input amplifier feedback as a function of a distance of an ungrounded fingertip ridge/valley pattern from said dielectric surface;
• and
• electrically grounded metal path means placed within said dielectric layer and below said ungrounded dielectric surface in a manner to be electrically isolated from and to physically surround each of said capacitor plates of each of said capacitance-cells.