A Fully-Integrated Wireless Bondwire Accelerometer With Closed-loop Readout Architecture

Abstract

This paper presents a fully-integrated wireless bondwire accelerometer using a closed-loop readout interface that effectively reduces the noise from electrical circuits and long-term frequency drifts. The proposed accelerometer was fabricated using 0.18- $\mu{\rm m}$ CMOS technology without micro electromechanical systems (MEMS) processing. To reduce manufacturing errors, the bondwire inertial sensors are wire-bonded on the chip pads, thereby enabling a precisely-defined length and space between sensing bondwires. The proposed wireless accelerometer using a pair of 15.2 $\mu{\rm m}$ and 25.4 $\mu{\rm m}$ bondwires achieves a linear transducer gain of 33 mV/g, bandwidth of 5 kHz, a noise floor of 700 $\mu{\rm g}/\surd{\rm Hz}$ , and 4.5 $\mu{\rm g}$ bias stability. The acceleration data is digitalized by an energy-efficient 10-bit SAR ADC and then wirelessly transmitted in real time to the external reader by a low-power on-off shift keying (OOK) transmitter. The proposed architecture consumes 9 mW and the chip area is 2 mm $\times$ 2.4 mm.