Qualcomm Incorporated

Maxim Integrated Products, Inc.

Synaptics Corporation

Ajay Taparia

Guozhong Shen

Ozan Ersan Erdogan

Syed Mahmud

Rajesh Anantharaman

Behrooz Javid

Rahim F Chowdhury

Erik Jonathon Thompson

Shunxi Wang

Rajesh Ananthararman

Aspects of the disclosure are directed to self-capacitance measurement and cancellation. In accordance with one aspect, a self-capacitance cancellation circuit includes an input amplifier, wherein the input amplifier comprises a non-inverting input, an inverting input and an output; a coherent current source coupled to the inverting input; a feedback network coupled to the output; and a capacitance coupled to the inverting input.

Dynamic range enhancement for self-capacitance measurement

An analog front end circuit utilizes coherent detection within a capacitance measurement application. The analog front end circuit uses coherent detection to measure capacitance of a touch screen display. An analog excitation signal is modulated by a capacitor to be measured. The modulated signal is synchronously demodulated using a correlator, which includes a discrete mixer and a discrete integrator. The excitation signal is also input to the mixer such that the modulated signal is multiplied by the excitation signal. The excitation signal is an analog signal having a sine wave function or other waveform.

Capacitive touch sense architecture having a correlator for demodulating a measured capacitance from an excitation signal

A method and device for providing a multi-modal capacitive sensor, including a plurality of sensor electrodes, in an electronic device is provided. In a first mode, the capacitive sensor is configured to capture an image of a biometric object. In a second mode, the capacitive sensor is configured to provide presence detection functionality. In the second mode, the capacitive sensor includes at least one first electrode and at least one second electrode selected from a plurality of sensor electrodes. When operating in the second mode, the at least one first electrode is configured to receive a transmit signal, and the at least one second electrode is configured to receive a resulting signal capacitively coupled from the at least one first electrode. Based on the resulting signal, a processing system of the electronic device determines whether a biometric object to be imaged is present in the sensing area.

Multi-mode capacitive sensor

A system includes a signal generator and a correlator. The signal generator outputs a first signal to a first end of a capacitance to be measured. The correlator is connected to an output of the signal generator that outputs the first signal and to a second end of the capacitance. The correlator receives the first signal from the output of the signal generator and receives a second signal from the second end of the capacitance. The correlator correlates the first signal and the second signal and generates an output signal based on a correlation between the first signal and the second signal. The output signal is proportional to a capacitance value of the capacitance.

Continuous time correlator architecture

A mixed signal correlator utilizes coherent detection within a capacitance measurement application. In some applications, the mixed signal correlator is used to measure capacitance of a touch screen display. An external capacitor whose capacitance is measured is kept small for improved sensitivity and can be used for a variety of applications having varied integration periods for measurement. The external capacitor is kept small and can be used for varied applications by adjusting the output voltage within a range that is less than the supply voltage, and maintaining a count of the adjustments to later reconstruct an actual output voltage for the integration period. An output is a weighted sum of an analog integrator output and a digital counter output.

Calibration for mixed-signal integrator architecture

An analog front end circuit utilizes coherent detection within a capacitance measurement application. The analog front end circuit uses coherent detection to measure capacitance of a touch screen display. An analog excitation signal is modulated by a capacitor to be measured. The modulated signal is synchronously demodulated using a correlator, which includes an integrated mixing and integration circuit. The correlator includes a programmable impedance element that generates a time-varying conductance according to a controlling digitized waveform.

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Santa Clara, CA, United States of America

Ajay Taparia