Abstract: An ultrasonic fingerprint sensor system of the present disclosure may be provided with an ultrasonic transmitter or ultrasonic transceiver having an electrode layer divided into a plurality of electrode segments. The ultrasonic fingerprint sensor system may detect an object over one or more electrode segments and provide a voltage burst to one or more selected electrode segments for localized generation of ultrasonic waves. The localized generation of ultrasonic waves may facilitate localized readout for imaging. In some implementations, the voltage burst may be provided in a single-ended drive scheme or differential drive scheme.

Abstract: A touchscreen display including a touchscreen panel with a set of spaced-apart electrically-conductive transmit lines and a set of spaced-apart electrically-conductive receive lines extending in orthogonal directions. A set of class-D transmit drivers generate transmit signals applied to the transmit lines based on a driving pulse-width-modulated (PWM) signals, respectively. The PWM signals control the amplitude, phase, and slew rate of the pulses of the transmit signals, respectively. The parameters of the pulses are controlled so that the transmit signals arrive with substantially the same amplitude, phase, and slew rate at each receiver regardless of which transmit driver generated the transmit signal. This allows a single anti-phase signal at each receiver to substantially cancel out the receive signal during no panel load.

Abstract: An interface circuit includes an amplifier having a first input, a second input, and an output, a drive capacitor coupled to the first input of the amplifier, and a feedback path coupled between the output of the amplifier and the second input of the amplifier. The interface circuit also includes a current driver coupled to the first input of the amplifier and the second input of the amplifier, wherein the current driver is configured to drive the drive capacitor with a first current, and to drive a touch panel capacitor coupled to the second input of the amplifier with a second current.

Abstract: In certain aspects, a bias generation circuit comprises a bias voltage generator. The bias voltage generator has a main NMOS transistor having a drain and a gate of the main NMOS transistor both coupled to a first terminal, a main resistor having a first main resistor terminal and a second main resistor terminal, wherein the first main resistor terminal couples to a source of the main NMOS transistor; and a main PMOS transistor having a source of the main PMOS transistor coupled to the second main resistor terminal and a drain and a gate of the main PMOS transistor both coupled to a second terminal, wherein the second terminal couples to a main ground. The bias generation circuit further comprises an array of sensors coupled to the first terminal and the second terminal.

Abstract: In certain aspects, a bias generation circuit comprises a bias voltage generator. The bias voltage generator has a main NMOS transistor having a drain and a gate of the main NMOS transistor both coupled to a first terminal, a main resistor having a first main resistor terminal and a second main resistor terminal, wherein the first main resistor terminal couples to a source of the main NMOS transistor; and a main PMOS transistor having a source of the main PMOS transistor coupled to the second main resistor terminal and a drain and a gate of the main PMOS transistor both coupled to a second terminal, wherein the second terminal couples to a main ground. The bias generation circuit further comprises an array of sensors coupled to the first terminal and the second terminal.

Abstract: An apparatus and method for efficiently increasing the signal-to-noise ratio of a biometric sampling system by implementing differential-sampling in successive differential-sampling operations and processing the output of the successive differential-sampling operations to create a biometric image. In some cases, the biometric image may be further noise-reduced by subtracting foreground-off and background-off data.

Abstract: In certain aspects, a bias generation circuit comprises a bias voltage generator. The bias voltage generator has a main NMOS transistor having a drain and a gate of the main NMOS transistor both coupled to a first terminal, a main resistor having a first main resistor terminal and a second main resistor terminal, wherein the first main resistor terminal couples to a source of the main NMOS transistor; and a main PMOS transistor having a source of the main PMOS transistor coupled to the second main resistor terminal and a drain and a gate of the main PMOS transistor both coupled to a second terminal, wherein the second terminal couples to a main ground. The bias generation circuit further comprises an array of sensors coupled to the first terminal and the second terminal.

Abstract: An interface circuit includes an amplifier having a first input, a second input, and an output, a drive capacitor coupled to the first input of the amplifier, and a feedback path coupled between the output of the amplifier and the second input of the amplifier. The interface circuit also includes a current driver coupled to the first input of the amplifier and the second input of the amplifier, wherein the current driver is configured to drive the drive capacitor with a first current, and to drive a touch panel capacitor coupled to the second input of the amplifier with a second current.

Abstract: A wide-tuning range low output impedance flip voltage follower (FVF) low dropout regulator (LDO) for large capacitor switching loads is disclosed. In some implementations, a touch sensing controller driver includes the LDO, which has an operational amplifier and a FVF. The FVF can have a gain device, a source follower device, and an adaptive level shifter coupled between a drain of the source follower device and a gate of the gain device.

Abstract: A touchscreen display including a touchscreen panel with a set of spaced-apart electrically-conductive transmit lines and a set of spaced-apart electrically-conductive receive lines extending in orthogonal directions. A set of class-D transmit drivers generate transmit signals applied to the transmit lines based on a driving pulse-width-modulated (PWM) signals, respectively. The PWM signals control the amplitude, phase, and slew rate of the pulses of the transmit signals, respectively. The parameters of the pulses are controlled so that the transmit signals arrive with substantially the same amplitude, phase, and slew rate at each receiver regardless of which transmit driver generated the transmit signal. This allows a single anti-phase signal at each receiver to substantially cancel out the receive signal during no panel load.

Abstract: A touchscreen controller includes a set of transmitters for generating transmit signals applied to electrically-conductive transmit lines of a touchscreen panel, and a set of receivers configured to receive the signals via electrically-conductive receive lines that are capacitively coupled to the transmit lines. Each receiver includes an integrator to integrate the received current signal to generate an output voltage used for determining a location, if any, of a finger or object touching the panel. The integrator includes input and output amplification stages, and a feedback capacitor coupled between an input and output of the cascaded amplification stages. The capacitance of the feedback capacitor is configured so that the integrator achieves a desired rejection of a received jammer current signal. To reduce the size of the feedback capacitor, a bypass amplification stage is provided to steer away some of the input jammer current from the input of the integrator.

Abstract: The present disclosure describes aspects of a capacitance-to-voltage modulation circuit. In some aspects, the circuit is used in touch sensing. In some aspects, a modulation circuit comprises a first pair of switches having one switch connected between a voltage source and a capacitor, and another switch connected between ground and the input of the circuit. The circuit also includes a second pair of switches having one switch connected between the voltage source and the input of the circuit, and another switch connected between ground and the capacitor. A third pair of the circuit's switches comprise one switch connected between the capacitor and an input of an analog-to-digital converter (ADC) and another switch connected between the input of the circuit and the input of the ADC. The third pair of switches may enable charge sharing of signals modulated by the first and second pairs of switches, a result of which can be used to sense touch input based on capacitance at the input of the circuit.

Abstract: A wide-tuning range low output impedance flip voltage follower (FVF) low dropout regulator (LDO) for large capacitor switching loads is disclosed. In some implementations, a touch sensing controller driver includes the LDO, which has an operational amplifier and a FVF. The FVF can have a gain device, a source follower device, and an adaptive level shifter coupled between a drain of the source follower device and a gate of the gain device.

Abstract: Certain aspects of the present disclosure provide a successive approximation register (SAR) analog-to-digital converter (ADC) implemented with a passive gain scaling architecture. Certain aspects provide a circuit for analog-to-digital conversion. The circuit generally includes a plurality of capacitive elements, a plurality of switches coupled to the plurality of capacitive elements, and SAR logic having an output coupled to control inputs of the plurality of switches. The circuit also includes a comparator having an output coupled to an input of the SAR logic, a sampling circuit coupled to an input node of the circuit, and a first capacitive element coupled in series between the sampling circuit and the plurality of capacitive elements.

Abstract: A wide-tuning range low output impedance flip voltage follower (FVF) low dropout regulator (LDO) for large capacitor switching loads is disclosed. In some implementations, the LDO includes an operational amplifier and a FVF. The FVF can have a gain device, a source follower device, and an adaptive level shifter coupled between a drain of the source follower device and a gate of the gain device.

Abstract: Apparatus and method for generating a DC pixel voltage are disclosed. The apparatus includes an amplifier configured to amplify an input signal to generate a voltage signal, wherein the input signal is generated in response to an ultrasonic wave reflecting off an item-to-be-imaged and propagating via a piezoelectric layer; a noise reduction circuit configured to pass the voltage signal from an output of the amplifier to a node, while reducing a propagation of noise from the output of the amplifier to the node; and a circuit configured to generate a DC pixel voltage based on the reduced-noise voltage signal.

Abstract: Apparatus and method for generating a DC pixel voltage are disclosed. The apparatus includes an amplifier configured to amplify an input signal to generate a voltage signal, wherein the input signal is generated in response to an ultrasonic wave reflecting off an item-to-be-imaged and propagating via a piezoelectric layer; a noise reduction circuit configured to pass the voltage signal from an output of the amplifier to a node, while reducing a propagation of noise from the output of the amplifier to the node; and a circuit configured to generate a DC pixel voltage based on the reduced-noise voltage signal.

Abstract: An apparatus, such as a pixel sensor for an ultrasonic imaging apparatus, is disclosed. The apparatus includes a first metallization layer coupled to a piezoelectric layer, wherein a first voltage is formed at the first metallization layer in response to an ultrasonic wave reflecting off an item-to-be-imaged (e.g., a user's fingerprint) and propagating through the piezoelectric layer, and wherein the first metallization layer is situated above a substrate; a second metallization layer situated between the first metallization layer and the substrate; and a device configured to apply a second voltage to the second metallization layer to reduce a parasitic capacitance between the first metallization layer and the substrate.

Abstract: The present disclosure describes aspects of a capacitance-to-voltage modulation circuit. In some aspects, the circuit is used in touch sensing. In some aspects, a modulation circuit comprises a first pair of switches having one switch connected between a voltage source and a capacitor, and another switch connected between ground and the input of the circuit. The circuit also includes a second pair of switches having one switch connected between the voltage source and the input of the circuit, and another switch connected between ground and the capacitor. A third pair of the circuit's switches comprise one switch connected between the capacitor and an input of an analog-to-digital converter (ADC) and another switch connected between the input of the circuit and the input of the ADC. The third pair of switches may enable charge sharing of signals modulated by the first and second pairs of switches, a result of which can used to sense touch input based on capacitance at the input of the circuit.

Abstract: Apparatus and method for generating a DC pixel voltage are disclosed. The apparatus includes an amplifier configured to amplify an input signal to generate a voltage signal, wherein the input signal is generated in response to an ultrasonic wave reflecting off an item-to-be-imaged and propagating via a piezoelectric layer; a noise reduction circuit configured to pass the voltage signal from an output of the amplifier to a node, while reducing a propagation of noise from the output of the amplifier to the node; and a circuit configured to generate a DC pixel voltage based on the reduced-noise voltage signal.