Design of 0.1‐mV zero‐g and 200‐μg/√Hz capacitance accelerometer with high sensitivity readout circuit with time‐to‐digital convertor applied to finger tremor of neurodegenerative disease

Abstract

AbstractFinger tremors occur in the early stage of brain disease such Parkinson's syndrome and dementia and are usually detected using inertial sensors such as triaxial gyroscopes or triaxial accelerometer to detect the finger tremor. But finger tremoring is a low‐acceleration and low‐frequency oscillation, and conventional gyroscopes and accelerometer cannot be used for the finger tremor detection. In this paper, we design and implement a single‐axis capacitance MEMS accelerometer, and a readout circuit with a Class AB amplifier with chopper technique and a time‐to‐digital convertor circuit with 1 bit for movement direction count and 8 bits for movement duration count. The proposed accelerometer and readout circuit can achieve 0.1‐mV low offset drift and 53‐mg offset at zero‐g, 200‐μg/√Hz noise density, and 720‐mV/g sensitivity. Mounting the proposed MEMS sensor on tremor index finger, measurement from time‐to‐digital convertor circuit shows twice time durations and a distinct count of changes in tremor finger movement. Monitoring movement durations through the proposed time‐to‐digital convertor circuit, it enables the clinicians to understand in a simple way whether finger tremors are associated with early dementia or Parkinson's syndrome, rather than just conventional amplitude voltage.