Three-axis MEMS accelerometer with built in ADC draws only 25 micro amps of current

Analog Devices has developed a new motion sensing device specifically for energy-constrained portable consumer products. The ADXL345 three-axis digital iMEMS (integrated micro-electro-mechanical system) accelerometer is the lowest-power device in its class, achieving an 80 percent power savings compared to competing three-axis inertial sensors. The ADXL345 also incorporates an on-chip ADC (analog-to-digital converter) that simplifies hardware configurations in wireless handsets, personal navigation devices and other mobile applications.

“Motion sensing has become a desirable technology for a range of mobile products: as cell phones add pedometer functions for health-conscious consumers; phones and digital cameras adopt landscape-to-portrait and horizon-orientation photo features; and mobile entertainment devices integrate wrist movement, shaking, rolling and other actions into the interactive gaming experience,” said Bill Murphy, product line director, Micromachined Products Group, Analog Devices. “ADI’s newest iMEMS product addresses two important pain points in these areas by lowering the current consumption of the ADXL345 to as little as 25 microamps and increasing the resolution across the entire measurement range.”

The ADXL345 motion sensor incorporates an on-chip FIFO (first-in/first-out) 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 new motion sensing devices save additional system power by off-loading 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 upwards of 75% of the budget, when utilized effectively.

About the ADXL345
The ADXL345 ultra-low-power digital accelerometer has an output data range that scales from 0.1 Hz to 3.2 kHz, unlike competing devices, which have fixed 100-Hz, 400-Hz, or 1-kHz data rates. This allows portable system designers to better manage energy consumption by precisely allocating power for a given system function and reserving unused power for other uses. The ADXL345 also 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-milli-g/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 new accelerometer also includes I²C and three- and four-wire SPI (serial peripheral interface) digital interfaces and a voltage range of 1.8 V to 3.6 V.

The ADXL345 three-axis iMEMS digital accelerometer is available today in pre-production quantities with volume production scheduled for March 2009. The ADXL345 comes in a small, thin 14-lead LFCSP and is priced at $3.04 in 1,000-unit quantities. For more information, visit http://www.analog.com/pr/ADXL345.