Abstract: Fingerprint detection circuits with common mode noise rejection are described. The Fingerprint detection circuit includes a half-bridge circuit coupled to a receive (RX) electrode of an array of fingerprint detection electrodes and to a buried capacitance that is unalterable by the presence of a conductive object on the array. The fingerprint detection circuit may also include a listener electrode configured to enable common mode noise rejection through a differential input stage of a low noise amplifier (LNA).

Abstract: A capacitance sensing device includes a transmit (TX) generator for generating a sequence of receive (RX) signals by applying each TX signal pattern in a sequence of TX signal patterns to a set of sensor electrodes. For each TX signal pattern in the sequence of TX signal patterns, and for each subset of three or more contiguous sensor electrodes of the set of sensor electrodes, the TX generator applies to the subset one of a first excitation signal and a second excitation signal. The plurality of subsets includes at least half of the sensor electrodes in the set of sensor electrodes. The capacitance sensing device also includes a sequencer circuit coupled with the TX generator. For each TX signal pattern in the sequence of TX signal patterns, the sequencer circuit determines a next subsequent TX signal pattern in the sequence based on a circular rotation of the TX signal pattern. The capacitance sensing device also includes a processing block coupled with the TX generator.

Abstract: A fingerprint sensor-compatible overlay material which uses anisotropic conductive material to enable accurate imaging of a fingerprint through an overlay is disclosed. The anisotropic conductive material has increased conductivity in a direction orthogonal to the fingerprint sensor, increasing the capacitive coupling of the fingerprint to the sensor surface, allowing the fingerprint sensor to accurately image the fingerprint through the overlay. Methods for forming a fingerprint sensor-compatible overlay are also disclosed.

Abstract: A touch sensing apparatus includes a touch sensing surface having a plurality of TX electrodes and a plurality of RX electrodes. The touch sensing apparatus also includes capacitance sensing circuitry. The circuitry receives a plurality of drive signals. For each of a plurality of scanning stages, the circuitry applies a respective one of the plurality of drive signals to each of the plurality of TX electrodes substantially simultaneously according to a respective TX pattern. The respective TX pattern for each scanning stage is distinct. The circuitry receives sense signals from the plurality of RX electrodes. Each of the plurality of sense signals represents capacitance of a respective intersection of a respective TX electrode and a respective RX electrode. The circuitry then correlates the received sense signals for the plurality of scanning stages with the received drive signals to detect an object proximate to the touch panel.

Abstract: A fingerprint sensor-compatible overlay material which uses anisotropic conductive material to enable accurate imaging of a fingerprint through an overlay is disclosed. The anisotropic conductive material has increased conductivity in a direction orthogonal to the fingerprint sensor, increasing the capacitive coupling of the fingerprint to the sensor surface, allowing the fingerprint sensor to accurately image the fingerprint through the overlay. Methods for forming a fingerprint sensor-compatible overlay are also disclosed.

Abstract: A capacitance sensing method includes generating a first set of currents by, for each transmit (TX) electrode of a set of TX electrodes, precharging a self capacitance of the TX electrode and a mutual capacitance between the TX electrode and a receive (RX) electrode of a set of RX electrodes by applying to the TX electrode a first excitation voltage corresponding to the TX electrode to induce a first current of the first set of currents, generating a second set of currents by, for each TX electrode, applying a reference voltage to the TX electrode to induce a second current of the second set of currents, and for each TX electrode, calculating a measure of the self capacitance of the TX electrode based on the second set of currents, and calculating a measure of the mutual capacitance between the TX electrode and each RX electrode based on the first set of currents.

Abstract: A capacitance sensing circuit may include a charge to digital converter, coupled to a signal receiver channel, to receive a signal from a capacitive sense array. The capacitance sensing circuit may also include a baseline compensation signal generator, coupled to the signal receiver channel, to provide a baseline compensation signal in an opposite phase of the signal to the signal receiver channel.

Abstract: A sensor-compatible overlay is disclosed which uses anisotropic conductive material to increase capacitive coupling of a conductive object through the overlay material to a capacitive sensor. The anisotropic conductive material has increased conductivity in a direction orthogonal to the capacitive sensor. In one embodiment, the overlay is configured to enclose a device which includes a capacitive sensor. In another embodiment, the overlay is configured as a glove.

Abstract: The sensing circuit includes including first input of a first electrode, a first set of inputs of a first set of two or more electrodes forming a first intersection and a second intersection, and a second set of inputs of a second set of two or more electrodes forming the second intersection and a third intersection. The sensing circuit includes a scan control circuit, coupled to the touch panel of electrodes, to concurrently select the sets of electrodes via a multiplexer. The touch sensing circuit includes an analog front end configured to generate digital values representative of mutual capacitances of a first and second unit cell, wherein the first unit cell comprises the first and second intersections and the second unit cell comprises the second and third intersections, and a channel engine configured to generate capacitance values corresponding to the unit cells.

Abstract: A method for detecting fingerprint spoof objects includes detecting a presence of the object at a fingerprint sensor and, in response to detecting the presence of the object, measuring a set of physical properties of the object based on one or more signals from a set of electrodes of the fingerprint sensor. The set of physical properties includes at least one of a subdermal compliance of the object and a surface adhesiveness of the object. The method further includes distinguishing the object as an actual finger or a spoof based on the one or more physical properties.

Abstract: A capacitance-sensing circuit may include a channel input associated with measuring a capacitance of a unit cell of a capacitive sense array. The capacitance-sensing circuit may also include a capacitive hardware baseliner that is coupled to the channel input. The capacitive hardware baseliner includes a programmable baseline resistor, and a buffer with an input coupled to the programmable baseline resistor and an output coupled to the channel input. The capacitive hardware baseliner generates a baseline current based on a time constant of the channel input associated with the measuring of the capacitance of the element of the capacitive sense array using the programmable baseline resistor. The capacitive hardware baseliner provides the baseline current at the channel input to provide a charge for a sense capacitor. A change in the charge of the sense capacitor is provided by the baseline current indicating a presence of a touch object proximate to the element.

Abstract: Techniques for multi-phase scanning based on pseudo-random sequences in capacitive fingerprint applications are described herein. In an example embodiment, a method performed by a processing device comprises: receiving measurements that are representative of a portion of a finger on a capacitive fingerprint sensor array, where the measurements are obtained from sensor elements of the capacitive fingerprint sensor array that are scanned in a multi-phase mode based on an excitation vector generated from a pseudo-random sequence; and generating a fingerprint image for the portion of the finger based on the measurements.

Abstract: A capacitance-sensing circuit may include a channel input associated with measuring a capacitance of a unit cell of a capacitive sense array. The capacitance-sensing circuit may also include a capacitive hardware baseliner that is coupled to the channel input. The capacitive hardware baseliner may generate a baseline current using a baseline capacitor and may provide the baseline current to the channel input.

Abstract: A sensor-compatible overlay is disclosed which uses anisotropic conductive material to increase capacitive coupling of a conductive object through the overlay material to a capacitive sensor. The anisotropic conductive material has increased conductivity in a direction orthogonal to the capacitive sensor. In one embodiment, the overlay is configured to enclose a device which includes a capacitive sensor. In another embodiment, the overlay is configured as a glove.

Abstract: A system comprising a sensing device and a capacitive sense array configured to detect a presence of a passive touch object and a stylus where the capacitive sense array receives a transmit signal from the stylus via capacitive coupling. The system further comprising a processing device configured to determine the stylus location on the capacitive sense array based on the transmit signal and to synchronize the stylus to the capacitive sense array. A system further comprises a demodulation block to extract additional data that is modulated into the transmit signal by the stylus. The demodulation block is configured to extract the additional data by amplitude shift keying. The additional data comprises at least one of an applied force value of the stylus tip, a button status data, a battery status data, or a stylus acceleration data.

Abstract: A method for improving noise immunity of capacitive sensing circuit associated with a touch sense array is disclosed. The capacitive sensing circuit receives a response signal from a touch sense array. The capacitive sensing circuit measures a noise component of the response signal. When a level of noise of the noise component within a passband of the capacitive sensing circuit is greater than a threshold, the capacitive sensing circuit changes at least one parameter of capacitive sensing circuit to move the passband substantially outside the frequency spectrum of the noise component.

Abstract: Techniques for fully-differential multi-phase scanning in capacitive fingerprint applications are described herein. In an example embodiment, a system comprises a capacitive fingerprint sensor array and a processing device coupled to the capacitive fingerprint sensor array. The processing device is configured at least to: scan the capacitive fingerprint sensor array in a fully-differential multi-phase mode; receive a plurality of measurements that represents a portion of finger on the capacitive fingerprint sensor array; and generate a fingerprint image for the portion of the finger based on the plurality of measurements. In some embodiments, a capacitive fingerprint sensor array may include receive (RX) electrodes and one or more reference electrodes configured to detect noise, where the one or more reference electrodes have width that is substantially equal to the width of the RX electrodes, but the one or more reference electrodes are disposed at a smaller pitch than the RX electrodes.

Abstract: Fingerprint detection circuits with common mode noise rejection are described. The Fingerprint detection circuit includes a half-bridge circuit coupled to a receive (RX) electrode of an array of fingerprint detection electrodes and to a buried capacitance that is unalterable by the presence of a conductive object on the array. The fingerprint detection circuit may also include a listener electrode configured to enable common mode noise rejection through a differential input stage of a low noise amplifier (LNA).

Abstract: A capacitance sensing circuit may include a charge to digital converter, coupled to a signal receiver channel, to receive a signal from a capacitive sense array. The capacitance sensing circuit may also include a baseline compensation signal generator, coupled to the signal receiver channel, to provide a baseline compensation signal in an opposite phase of the signal to the signal receiver channel.

Abstract: A fingerprint sensor-compatible overlay which uses anisotropic conductive material to enable accurate imaging of a fingerprint through an overlay is disclosed. The anisotropic conductive material has increased conductivity in a direction orthogonal to the fingerprint sensor, increasing the capacitive coupling of the fingerprint to the sensor surface, allowing the fingerprint sensor to accurately image the fingerprint through the overlay. In one embodiment, the overlay is configured to enclose a device which includes a fingerprint sensor. In another embodiment, the overlay is configured as a glove. Methods for forming a fingerprint sensor-compatible overlay are also disclosed.