Qualcomm Incorporated

Maxim Integrated Products, Inc.

Rahim F Chowdhury

Guozhong Shen

Ozan Ersan Erdogan

Syed Mahmud

Rajesh Anantharaman

Ajay Taparia

Behrooz Javid

David Castaneda

Bo Yang

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

Digital to analog converters having a hybrid two-stage structure. The first stage is a differential segmented current DAC controlled by the MSBs (most significant bits) of input data. The second stage is a resistor string DAC controlled by the LSBs (least significant bits) of the input data to interpolate between the differential outputs of the first stage. The resistor string is directly connected to the current DAC without the need of buffer amplifiers. Instead, a replica circuit is used to prevent the second-stage resistor string from loading the first stage current DAC. Compensation techniques are described.

Replica compensated heterogeneous DACs and methods

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Saratoga, CA, United States of America

Rahim F Chowdhury