Maxim Integrated Products, Inc.

Paul W Kalthoff

Jerzy Antoni Teterwak

Geir Ostrem

A capacitive sensing system are configured to sense a capacitance value and convert the sensed capacitance value to a digital format. The capacitive sensing system provides good selectivity and immunity to noise and interference, which can be further enhanced by enabling spread spectrum excitation. In some embodiments, the capacitive sensing system utilizes a sinusoidal excitation signal that results in low electromagnetic emissions, limited to narrow frequency band. In some embodiments, the capacitive sensing system is configured to operate in a spread spectrum mode, in which the majority of the excitation signal power is carried in the assigned bandwidth. The excitation frequency and the bandwidth of the spread spectrum excitation signal are programmable in a wide range, which allows for avoiding frequency conflicts in the operating environment.

Method and apparatus for sensing capacitance value and converting it into digital format

Low distortion current switches for high speed current steering digital-to-analog converters. The current switches use a compensation method for improving the spurious peformance of a CMOS current steering DAC for high output frequencies caused by the capacitance of the common node of the switch transistors. For this purpose, a replica switch is provided, with the voltage change on the common node of the replica switch being used to provide a corresponding charge to the common node of the main switch in an amount equal to the charge needed to change the voltage on the common node of the main switch by the same amount as the voltage change on the common node of the replica switch. Multiple embodiments are disclosed.

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Colorado Springs, CO, United States of America

Paul W Kalthoff