A 2.5-rad/s/sup 2/ resolution digital output MEMS-based rotational accelerometer for HDD applications

A 2.5-rad/s/sup 2/ resolution micro-electro-mechanical system-based rotational accelerometer targeted for hard disk drive (HDD) application is presented. The device is composed by a 0.6-/spl mu/m BiCMOS electronic interface that implements together with the MEMS sensor one single bit electromechanical /spl Sigma//spl Delta/ conversion loop able to detect capacitive unbalancing as low as 50 aF (50/spl middot/10/sup -18/ F). The produced bitstream is then processed by a digital chain and made available through a standard three-wire digital interface. The device is intended for feedforward compensation of external disturbances acting on computer HDDs to steadily keep the read-write heads on track and to allow greater track densities.