Abstract: A method for detecting a finger at a fingerprint sensor includes detecting a presence of an object at a fingerprint sensor and, in response to detecting the presence of the object, acquiring image data for the object based on signals from the fingerprint sensor. The method further includes, for each subset of one or more subsets of the image data, calculating a magnitude value for a spatial frequency of the subset, and identifying the object as a finger based on comparing the magnitude value to a threshold.

Abstract: A fingerprint sensing circuit, system, and method is disclosed. The fingerprint sensor maybe include a plurality of inputs coupled to a plurality of fingerprint sensing electrodes and to an analog front end. The analog front end may be configured to generate at least one digital value in response to a capacitance of at least one of the plurality of fingerprint sensing electrodes. Additionally, the analog front end may include a quadrature demodulation circuit to generate at least one demodulated value for processing by a channel engine. The channel engine may generate a capacitance result value that is based, in part, on the demodulated value and is stored in a memory.

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 capacitive sensor may include a transmit electrode and a receive electrode capacitively coupled with the transmit electrode. A capacitance sensing circuit senses a capacitance between the transmit and receive electrodes by applying a signal to the transmit electrode and rectifying a current waveform induced at the receive electrode. A compensation circuit reduces the effect of a mutual and parasitic capacitances of the transmit and receive electrode pair by adding a compensation current to the rectified current.

Abstract: A system comprises a processing device and a capacitive sense array that includes a plurality of electrodes. The system performs a first scan of a plurality of electrodes in a capacitive sense array to determine a position of a stylus. The system also performs one or more additional scans of subsets of the plurality of electrodes to determine additional positions of the stylus. The system may continually perform the additional scans on of the subsets of the plurality of electrodes until the stylus is no longer detected.

Abstract: A fingerprint sensing circuit, system, and method is disclosed. The fingerprint sensor maybe include a plurality of inputs coupled to a plurality of fingerprint sensing electrodes and to an analog front end. The analog front end may be configured to generate at least one digital value in response to a capacitance of at least one of the plurality of fingerprint sensing electrodes. Additionally, the analog front end may include a quadrature demodulation circuit to generate at least one demodulated value for processing by a channel engine. The channel engine may generate a capacitance result value that is based, in part, on the demodulated value and is stored in a memory.

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: Apparatus and methods of active stylus to host device data transmitting are described. One method receives, at a stylus, an indication that a host device is performing a first coordinate measurement operation to determine a coordinate of the stylus proximate to a capacitive sense array of the host device. The set of coordinate measurement operations includes a first measurement operation of a first set of electrodes of the capacitive sense array and a second measurement operation of a second set of electrodes of the capacitive sense array. While the host device is performing the set of coordinate measurement operations, the stylus transmits a data packet of stylus data to the host device. In particular, the stylus transmits a first bit of the data packet during the first measurement operation and transmits a second bit of the data packet during the second measurement operation.

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 sensing circuit, system, and method is disclosed. The fingerprint sensor maybe include a plurality of inputs coupled to a plurality of fingerprint sensing electrodes and to an analog front end. The analog front end may be configured to generate at least one digital value in response to a capacitance of at least one of the plurality of fingerprint sensing electrodes. Additionally, the analog front end may include a quadrature demodulation circuit to generate at least one demodulated value for processing by a channel engine. The channel engine may generate a capacitance result value that is based, in part, on the demodulated value and is stored in a memory.

Abstract: A capacitive sensor includes a switching capacitor circuit, a comparator, and a charge dissipation circuit. The switching capacitor circuit reciprocally couples a sensing capacitor in series with a modulation capacitor during a first switching phase and discharges the sensing capacitor during a second switching phase. The comparator is coupled to compare a voltage potential on the modulation capacitor to a reference and to generate a modulation signal in response. The charge dissipation circuit is coupled to the modulation capacitor to selectively discharge the modulation capacitor in response to the modulation signal.

Abstract: A system comprises a processing device and a capacitive sense array that includes a plurality of electrodes. The system receives a first signal from a first scan of electrodes in a capacitive sense array. The system processes the first signal using a first set of sequences to detect a stylus. The system receives a second scan from a second scan of electrodes in a capacitive sense array. The system processes the second signal using a second set of sequences to detect the stylus.

Abstract: An apparatus for and a method of sensing capacitance of one or more sensor elements in multiple capacitance sensing modes, including a self-capacitance sensing mode and a mutual capacitance sensing mode.

Abstract: A system comprises a processing device and a capacitive sense array that includes a plurality of electrodes. The system performs a first scan of a plurality of electrodes in a capacitive sense array to determine a position of a stylus. The system also performs one or more additional scans of subsets of the plurality of electrodes to determine additional positions of the stylus. The system may continually perform the additional scans on of the subsets of the plurality of electrodes until the stylus is no longer detected.

Abstract: A method can include determining multiple sensed positions of an object path in a touch sense region; generating at least a first predicted position from the sensed positions; and filtering a sense position, including associating the sense position with the object path if it is within a first proximity to at least the first predicted position, and not associating the sense position with the object path if it is outside of at least the first proximity from the first predicted position.

Abstract: A system and method for synchronizing a stylus to a capacitive sense array. The system including a capacitive sense array which includes a plurality of electrodes. A synchronization signal is transmitted to the stylus using the plurality of electrodes. The synchronization signal is transmitted to the stylus by capacitively coupling the stylus to the capacitive sense array.

Abstract: A system and method for synchronizing a stylus to a capacitive sense array. The system including a capacitive sense array which includes a plurality of electrodes. A synchronization signal is transmitted to the stylus using the plurality of electrodes. The synchronization signal is transmitted to the stylus by capacitively coupling the stylus to the capacitive sense array.

Abstract: A capacitive sensor includes a switching capacitor circuit, a comparator, and a charge dissipation circuit. The switching capacitor circuit reciprocally couples a sensing capacitor in series with a modulation capacitor during a first switching phase and discharges the sensing capacitor during a second switching phase. The comparator is coupled to compare a voltage potential on the modulation capacitor to a reference and to generate a modulation signal in response. The charge dissipation circuit is coupled to the modulation capacitor to selectively discharge the modulation capacitor in response to the modulation signal.