Low noise floor aids accelerometer tilt resolution

Edited by the Engineeringtalk editorial team May 29, 2002

An ultra-low-noise device is the latest in the successful line of standard submicron CMOS accelerometers from Memsic.

An ultra-low-noise device is the latest in the successful line of standard submicron CMOS accelerometers from Memsic.

Because of its low noise floor and high degree of accuracy, the new accelerometer has proven to be well suited for automotive applications - such as car alarms, rollover, and navigational devices - and in consumer electronics, such as PDAs, cellphones and global positioning systems (GPS).

"We have found that these markets in particular have a strong need for the ultra-low-noise accelerometer", said Yang Zhao, CEO of Memsic.

"As with all of Memsic's products, our standard CMOS structure cuts costs by up to 50%; in addition, the ultra-low-noise accelerometer offers unparalleled low noise resolution due to its low noise floor, eliminates the need for external offset adjustments because of its tighter offset, and can allow tilt angles approaching 1 degree to be measured, improving accuracy and reliability of products that rely on tilt".

The ultra-low-noise accelerometer is based on heat convection and requires no proof mass, eliminating stiction and particle problems associated with other devices.

Because Memsic has successfully integrated MEMS technology with leading-edge IC processes to create MEMS ICs, the ICs are fully programmable at the end of the manufacturing cycle and integrate the electronics and sensor on the same IC, saving customers money and space - a significant benefit for manufacturers of small electronic devices such as cellphones and PDAs.

On of the cutting-edge applications in the cellular market today is scalable vector graphics (SVG).

This new technology makes it possible to take web pages and other graphic formats, scale them, and transfer them to a PDA or cellphone.

"Our accelerometers are very appropriate for this new technology because it simplifies how the end user views the downloaded pages", said Zhao.

"Instead of having to scroll through a web page or map, the user can tilt or move their cellphone or PDA in any direction and the device will automatically scroll based on the user's motion.

If the user wants to zoom in or zoom out on the page, all he or she needs to do is pull the device closer or move it farther away".

Another application that requires a low noise floor and high sensitivity to tilt is navigational, or GPS, systems for the handheld and automotive industry, a market estimated at seven million units annually that is expected to grow to 10 million units by 2004.

The ultra-low-noise accelerometer is used in dead reckoning modules that supplement GPS satellite signals as a tilt sensor to correct digital compass readings.

"The accelerometer in these devices monitors motions and distance travelled during absence of the GPS signal", Zhao said.

"Because of its tight offset, our accelerometer is extremely useful for these products because the device does not need to be level to give an accurate reading".

The Memsic ultra-low-noise accelerometer is in production today and priced at: $8 each for 1000 units; $3.05 each for 100,000 units; and approaching $2 per unit for one million units.