Tommaso Ungaretti

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

A 0.6 /spl mu/m BiCMOS interface for microelectromechanical systems (MEMS) based rotational accelerometers is presented. It is housed in an inexpensive standard SO-24 plastic package with a capacitive rotational accelerometer sensor produced using MEMS technology. This sensitive interface chip includes the analog-to-digital conversion, filtering, and interface functions. The analog-to-digital conversion is realized through a single-bit electromechanical /spl Sigma/-/spl Delta/ loop able to detect capacitive unbalancing as low as 50 aF (50/spl times/10/sup -18/ F). The produced bitstream is then processed by a digital chain and made available through a standard 3.3 V (5 V tolerant) three-wire serial bus. The signal bandwidth is about 800 Hz, the sensitivity is 2.5 rad/s/sup 2/, with a full-scale sinewave of 200 rad/s/sup 2/ and a signal-to-noise ratio peak of 38 dB over 30-800 Hz. Through the serial bus, it is also possible to program device characteristics including gain, offset, filter performance, and phase delay. The complete sensor is used in a feed-forward compensation scheme to cancel external disturbances acting on computer hard-disk drives so as to steadily keep the read-write heads on track: this allows greater track densities and better speed performance.

A low power CMOS interface circuit for three-axis integrated accelerometers

A CMOS interface for three-axis capacitive accelerometers is presented. The circuit implements an innovative readout approach which allows to obtain a power consumption much lower than traditional schemes, thanks also to the reduced circuit complexity. A total power consumption of 175 muW at the nominal supply voltage 2.5 V is obtained for the entire interface.

Motion MEMS and Sensors, Today and Tomorrow

Only 6 years passed since the dawn of the Motion Sensors Era in the Consumer market and now the world of MEMS Motion Sensors is completely different and it’s going to change even more in the future. If 2006 was the year of the Accelerometer adoption by NintendoTM in the WiiTM Controller, 2010 was the year of the Gyroscope adoption by Smartphone manufacturers. And in both cases STMicroelectronics triggered the big volume production of those two micro-machined devices, previously known only by automotive customers and used only for active and passive safety applications. Moreover nowadays combinations of these two inertial products, also known as Six Degree-Of-Freedom Motion Sensors 6XDOF, are starting to appear in the market and most likely they will coexist with standalone accelerometers and gyroscopes, depending on customer needs in terms of compactness and performances. This paper reports the details of an innovative tri-axis silicon MEMS Coriolis’ gyroscope that fulfills the pressing market requirements for low power consumption, small size, slim form factor, high performances and low cost, but it addresses also the recent trends of the Six Degree-Of-Freedom 6XDOF and Nine-Degree-of-Freedom 9XDOF systems, realized by integrating the 6XDOF with a compass.

A Low-g 3 Axis Accelerometer for Emerging Automotive Applications

A 30 µg/sqrt(Hz) resolution MEMS based low-g 3-axis accelerometers targeted for emerging automotive application is presented. The device is composed by 2-dice in a single package: the sensing element and the processing IC. The sensing element is realized with an epitaxial micro-machining process (ThELMA™) while the IC uses a 0.5 μm BICMOS process. The IC amplifier is able to detect capacitive changes as low as 10 aF (10·10−18 F) and the device is able to provide both an analog and a digital output. Moreover it has very good linearity and very low cross talk between the sensing axes thanks to a design that fits very well the ST micro-machining process ThELMA. Finally, the proposed interface accelerometer is factory-trimmed to ensure repeatable performance without production-line adjustments in the end product