Capacitive interface circuit for low power sensor system

Abstract

This disclosure describes a capacitive interface circuit for a low power system. The capacitive interface circuit is configured to achieve very low noise sensing of capacitance-based transducers, such as a micro-electro-mechanical system (MEMS)-based sensor, with high resolution and low power. The capacitive interface circuit uses a differential amplifier and correlated triple sampling (CTS) to substantially eliminate, or at least reduce, kT/C noise, as well as amplifier offset and flicker (1/f) noise, from the output of the amplifier. The capacitive interface circuit may further include an output stage that reduces glitching, i.e., clock transients, in the output signal by allowing transients in the amplifier output to settle. In this manner, the circuit can be used in a low power system to produce a stable, low-noise output.

Description

technical field [0001] [0001] The present invention relates to sensor interface circuits, and more particularly to capacitive interface circuits for low power sensor systems. Background technique [0002] [0002] In micromechanical systems, such as microelectromechanical systems (MEMS) sensors, variable capacitors are used as an interface between sensors, such as accelerometers, gyroscopes, pressure sensors, humidity sensors, or other types of micro mechanical sensor. Such sensors have a wide variety of applications, including industrial monitoring, environmental monitoring, and / or physiological monitoring. Physiological monitoring has various biomedical applications including posture, activity, pace, venous pressure, intracranial pressure, heart sounds, and more. [0003] [0003] In an accelerometer, for example, a capacitive plate may be formed by fingers coupled to a beam structure of a proof mass and designated fingers coupled to an inertial frame. The set of fingers in...

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Problems solved by technology

Giving up kT/C noise allows lower inter

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