Norwood, Mass. — Analog Devices, Inc. said its new ADXL330, 3-axis accelerometer, is the industry's lowest power device of its kind, typically consuming only 200 microamps at full power at a supply voltage of 2.0 V. Combined with a small surface-mount 4 x 4 x 1.45-mm package, the new device aims to be the sensor of choice for a variety of portable consumer devices, particularly mobile phones, by offering designers the ability to deliver new motion and tilt sensing features.
"We're targeting the handset market and other portable devices where low power, small package and very low cost are probably three of most important things that customers are asking for in these high-volume applications," said Mack Lund, product manager, Micromachined Products Division, Analog Devices. "We've seen very high growth in consumer applications, although historically our business was based largely on crash [automotive airbag] sensors but that has been changing over the past couple of years."
The ADXL330 3-axis accelerometer, which also integrates signal conditioning on the same die, is capable of measuring the static acceleration of gravity for tilt-sensing applications, as well as dynamic acceleration resulting from motion, shock, or vibration with a ±2 g range. In addition, it offers a high shock rating of 10,000 g. With a supply voltage range of 2.0 V to 3.6 V, the new device is compatible with applications requiring bandwidths ranging from 0.5 Hz to 1.6 kHz.
"This is the first single-chip, 3-axis integrated MEMS accelerometer, where we integrate both the signal conditioning as well as the physical, mechanical sensor structures on the same silicon die, using our technology," Lund said.
A key characteristic of the ADXL330 is its low power requirements. It consumes 200 microamps at 2.0 V and 320 microamps at 3.0 V. ADI said it was able to reduce the power requirements by leveraging the company's iMEMS process technology and using innovative design techniques to implement circuit configurations for very low power and small sensor designs. Based on competitive benchmarking, the company believes the new 3-axis sensor offers the lowest power in its class.
"Specified at a 3-volt supply, which is where many customers may choose to use the device, it still comes in at less than one milliwatt but we do believe there is a large class of customers who will want to move to lower supply voltages which is why we completed characterization at a 2-volt supply. At this level we use only about 200 microamps typical for an amazing 400 microwatts of power," Lund said.
Duty cycling is also available for lower bandwidth applications to further lower power consumption, he said.
ADXL330 is pin-for-pin compatible with dual-axis device (with added Z-axis output)
(Click on Image to Enlarge)
3-axis sensor opportunities
While single- and dual-axis applications will not disappear, Lund believes 3-axis sensing will open up a host of new application opportunities, particularly in the areas of enhanced user interfaces, improved power management and high-shock resistance. "It will allow users to totally change the way they use their phones and other devices," he said.
The three-primary sensing areas for the new three-axis sensor are motion, tilt and shock. New applications include mobile phones with motion-sensing user interfaces and situational-aware functions such as "smart" power management, notebook computers and media players with disk drive protection systems, motion-enabled gaming devices, and digital still cameras that sense position and motion to help users take better pictures. The device has already been designed into several next-generation products.
A key factor driving the need for 3-axis sensing is the fact that a user can utilize a portable device in many different orientations so it doesn't have an inherent reference frame, Lund said. The third axis will enable greater flexibility and capabilities and allow a user to leverage many types of applications, he added.
"For example, you might be able to do tilt scrolling of menus so as you tilt your device you automatically scroll through a menu, or you might be able to sense the position of the device, such as if it has been sitting motionless on a table for a long period of time, allowing you to put it into a very low power mode to conserve battery life," he added.
"We also see the need for smaller, thinner packages and increased functionality needs — digital interfaces, and additional programmability being built into the accelerometer," Lund said.
Still, price will be a big factor in adoption of the new 3-axis technology. "We see the trend opening up as the price points come down, Lund said.
Based on Analog's product roadmap for this core three-axis sensing technology, Lund fully expects that the company will be able to bring pricing down below the $1.00 price point "which many of the handset makers have told us is key in obtaining the most widespread adoption of these types of features."
The ADXL330 is offered in a 16-lead, plastic lead-frame chip-scale package (LFCSP). In the future, the company predicts a need for thinner packages, and has already demonstrated thinner LFCSP packages of 4 x 4 x .9-mm, which will be pin-for-pin compatible with the standard LFCSP package. This new package is expected to be available next year, followed by a smaller and even thinner 2 x 2 x .6-mm wafer scale package in about a two-year time frame.
The ADXL330 is priced at below $2.00 for high-volume consumer applications. Samples are available with volume production scheduled in first quarter 2006. The datasheet and other information can be found at: www.analog.com/ADXL330
Analog Devices Inc., 781-937-1302, www.analog.com
