Inertial measurement unit is low power, small size

1 min read

Looking to address motion control applications where accuracy at low power is important, Fairchild has launched the FIS1100, a six axis MEMS inertial measurement unit that takes advantage of its investments in MEMS and motion tracking.

Per Slycke, vp of motion tracking, said: "We're excited about adding a new line of MEMS devices to our portfolio. The FIS1100 is focused on delivering a complete solution for applications that need to check motion in 3D."

According to Slycke, the part has been designed to provide high accuracy, but not at the expense of power consumption. "Motion sensors are capable of streaming a lot of data, but if you don't design the system carefully, you can burn a lot of power processing that data."

Power consumption is said to be minimised through an integral ASIC called the AttitudeEngine. This vector motion processor works with nine-axis sensor fusion algorithms to provide a system level solution with up to ten times lower processing power consumption in a range of applications.

"Many applications, including robotics and virtual reality, need a certain level of accuracy," Slycke noted. "At the same time, these apps are power sensitive."

Data is captured by a gyroscope and accelerometer – each with three axes – implemented on the same device layer. This is combined with data from an external three axis magnetometer and processed by the AttitudeEngine.

"In a traditional approach," Slycke said, "data is streamed at around 1kHz. However, the AttitudeEngine preprocesses data and streams it to the host at the rate demanded by the app."

The device layer is 60µm thick, with a high aspect ratio providing a good signal to noise ratio. "But it's harder to make," Slycke said, "because it needs deep etch."

While the gyro needs a vacuum, the accelerometer needs a damping atmosphere to prevent ringing. The two cavities are separated by caps, with a getter in the gyro chamber maintaining the vacuum.

Because it was looking for the smallest footprint possible, Fairchild has stacked the MEMS and ASIC dice, connecting them using through silicon vias. This enables the part to be supplied in a 3.3 x 3.3 x 1mm package.

"We are ambitious about our plans," Slycke concluded. "We have made big investments and the learning curve is behind us. We have a platform in place and will be responsive to market requirements."