Electronic Design

Tiny, Scalable Accelerometers Include Smart Embedded Features

STMicroelectronics utilized micro-electro-mechanical systems (MEMS) technology to create a family of three-axis linear accelerometers that come housed in a 3- by 3- by 1-mm package (see the figure). The sensors produce digital output and boast resolution scalability, smart embedded features, and reduced power consumption. They target a wide range of low-g applications, including motion user interfaces or pedometers in mobile phones, gaming devices, remote controllers, or portable media players.

All three devices (LIS331DLH, LIS331DLM, and LIS331DLF) integrate smart embedded features such as low power mode, auto wake-up function, free fall motion and 6D-orientation detection, as well as a standard serial peripheral interface (SPI)/I2C digital interface. The 6D recognition signals if the accelerometer is up or down along all three axes (x,y,z). This information can be used, for example, to automatically mute a phone when it is upside down. Resolution scalability means that users can select a 6-, 8-, or 12-bit device, all pin-to-pin, motion, and software compatible so they can be reused across different projects without the need to change the board and sensor software drivers.

The accelerometers can be programmed to work in the sleep-to-wake mode in which the device keeps the read chain active, consuming less than 10 µA, and automatically wakes up when an event occurs. Two separate, programmable interrupt signals enable immediate notification of free fall, motion, or 6D events.

Samples of the LIS331DLH, LIS331DLM, and LIS331DLF are available now, with volume production starting from early 2009. Unit pricing is around $1.50 in 100,000-piece quantities.


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