MEMS accelerometer draws only 300nA in motion-activated wake-up mode

June 05, 2012 // By Julien Happich
Analog Devices has unveiled an ultra-low power 3-axis MEMS accelerometer that consumes 2µA at a 100Hz output data rate, and only 300nA in motion-triggered Wake-Up mode.

Unlike accelerometers that use power duty cycling to achieve low power consumption, the ADXL362 does not alias input signals by undersampling; it samples the sensor's full bandwidth at all data rates.

This extremely low power consumption allows the ADXL362 to be used in applications that require battery life expectancy of years or decades, and where battery replacement can be impractical or dangerous to the equipment or operator. The part can be used as a motion-activated switch to manage total system power by turning system functions on and off at precisely the correct time, depending on activity level, or predefined motion thresholds.

Equipped with an Awake Status output pin, the motion sensor can instantly trigger a switch that turns on system functions, bypassing the processor in applications where power savings is critical. The device also integrates an enhanced, multiple-sample activity detection function that more accurately distinguishes between different kinds of motion. This eliminates false positives and prevents the sensor from turning the system on unnecessarily and costing additional battery life. The ADXL362 MEMS accelerometer embeds a deep internal FIFO memory block that allows system designers to record data and stream long data sets, reducing processor load and saving additional system power.

Two lower-noise modes that allow the user to about halve the noise at the expense of a few microamps (μA); a built-in micro-power temperature sensor; and the ability to synchronize the sampling time to an external trigger. The ADXL362 natively provides acceleration data with 12-bit resolution, and also provides 8-bit formatted data for more efficient single-byte transfers when a lower resolution is sufficient. The accelerometer has measurement ranges of ±2 g, ±4 g, and ±8 g, with a resolution of 1 mg/LSB on the ±2 g range. The ADXL362 operates on a wide 1.6 V to 3.6 V supply range and can interface, if necessary, to a host operating on a separate, lower supply voltage. Its standby power is 10nA.