MEMS-based motion sensor

1 April 2009 Analogue, Mixed Signal, LSI

Analog Devices has developed a new MEMS-based motion sensing device specifically for energy-constrained portable consumer products. The ADXL345 three-axis digital iMEMS accelerometer also incorporates an on-chip ADC that simplifies hardware configurations.

The motion sensor incorporates an on-chip FIFO memory block that stores up to 32 sample sets of X, Y and Z data. By sampling input data to determine if the system should be actively responding to a change in movement or acceleration, the devices save additional system power by offloading that function from the host processor. Typically, a host processor consumes a dominant amount of system power budget, so allowing it to remain in sleep mode as long as possible can dramatically decrease overall power usage when utilised effectively.

The ADXL345 has an output data range that scales from 0,1 Hz to 3,2 kHz. It measures dynamic acceleration resulting from motion or shock and with a 10 000 G shock rating is well suited for applications such as hard-disk drive protection in personal computers. Featuring resolution of 4 milliG/lsb (least-significant bit) across all G ranges, single tap and double tap detection, activity and inactivity detection, free fall detection, and user-programmable threshold levels, the accelerometer also includes I²C and three- and four-wire SPI digital interfaces and a voltage range of 1,8 V to 3,6 V.

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