A MEMS-based rotational accelerometer for HDD applications with 2.5rad/sec2resolution and digital output

A 0.6µm BiCMOS interface for MEMS based rotational accelerometers is presented. The interface implements together with the MEMS sensor one single bit electromechanical ΣΔ conversion loop able to detect capacitive unbalancings as low as 50aF (50.10^-18F), which corresponds to a rotational acceleration of 2.5rad/sec². The produced bitstream is then processed by a digital chain and made available through a standard 3-wires digital interface. The device is intended for feed-forward compensation of external disturbances acting on computer HDDs so to steadily keep the read-write heads on track and to allow greater track densities.