Accelerometer Design Using MOS Ring Oscillator

Abstract

A digital accelerometer is developed by using a ring oscillator (RO) and a mixer. The sensitive unit of the accelerometer is the metal-oxide semiconductor (MOS) ROs located on silicon beams. Based on the piezoresistive effect of the MOS RO, the accelerometer transduces the acceleration into frequency output. The syntonic frequency of the MOS RO changes in relation to many environmental elements, such as temperature, source voltage, and so on. The mixer is an interior signal processor that improves the output signal characteristics, with the digital output signal representing the frequency change. As the accelerometer is based on the piezoresistive effect of the MOS RO, the frequency characteristics of the MOS RO and its relationship with the acceleration are described. The device has been fabricated using standard integrated circuits processing methods combined with the Micro-Electro-Mechanical Systems process. The characteristics of the sample chip are in agreement with the theoretical predictions. The accelerometer has a high sensitivity of 6.91 kHz/g, a low temperature coefficient, and a simple fabrication process.