Reference designs rule
The consumer-device makers buying all those chips, according to Melzer, are telling Bosch-Sensortec that they want reference designs showing how to utilize MEMS chips in multiple ways. For instance, cell phones are predicted to consume as many as 10 billion MEMS chips by 2010,
according to Philippe Kahn, founder of Fullpower Technologies Inc. (Santa Cruz, Calif.). Cell phones will use accelerometers to perform user-interface duties, such as picking-up the phone by shaking it, as well as to perform secondary tasks, such as extending battery life with intelligent power management that turns off the cell phone's display
when its laid face down.
Beyond using a single MEMS chip for multiple tasks is using multiple sensor chips for a single task. Here, STMicroelectronics agrees with Bosch-Sensortec, according to Jay Esfandyari, MEMS market development manager at STMicroelectronics. As an example, Esfandyari has recently been demonstrating a reference design for an electronic compass that compensates for tilt using a three-axis accelerometer. Normally, a magnetometer chip requires that you keep it flat to read-out a compass heading correctly, but an accelerometer can sense orientation and compensate. STMicroelectronics' reference design shows the compensating compass heading in bold, with a lighter indicator showing how much the compass would be off if it wasn't equipped with the accelerometer.
Bosch-Sensortec is currently putting together another multi-mode reference design that points the way for OEMS using its chips for next-generation consumer-electronic devices. In particular, Bosch-Sensortec is working with the navigational device maker NumeriX S.A. (Manno, Switzerland) to combine a Bosch-Sensortec MEMS barometric-pressure sensor with NumeriX's global-positioning system (GPS) chip set.
"We make the world's smallest digital-pressure sensors, which we are integrating with GPS navigation solutions from NumeriX," said Melzer. "The SMD500 pressure sensor can detect changes in height as small as one foot, which helps when navigating stacked freeways and facilitates timely notification of upcoming exits. A pressure sensor can also help distinguish between closely packed freeway clover-leafs by detecting the slope of the road," said Melzer.
By integrating Bosch's SMD500 barometric pressure sensor with NumeriX GPS chips, the NumeriX/Bosch reference design achieves higher resolution for more accurate "turn" commands, as well as allowing multilevel bridges and stacked highways to be more easily navigated.