7-Axis Combo Sensor Costs 10% Less Than a Component Solution

InvenSense, now part of TDK, introduced the industry’s first 7-axis combo sensor that integrates a 6-axis inertial sensor (incorporating a 3-axis gyroscope and a 3-axis accelerometer) and a MEMS capacitive barometric pressure sensor. Targeting drone and other motion tracking applications, the new 7-axis motion tracking device can cut costs, save board space and deliver a better response time.

The new ICM-20789 7-axis combo sensor, housed in a 4-mm x 4-mm x 1.37-mm land grid array (LGA) package, touts the industry’s lowest pressure noise of 0.4 Pa RMS and a temperature coefficient of ±0.5 Pa/°C.

System Plus Company, a reverse costing company, recently conducted a cost analysis of the new 7-axis combo sensor, which found the new device costs 10 percent less than a comparable 6-axis motion tracking & pressure sensor system.

The new InvenSense device is a good example of a tech breakthrough, delivering a 7-axis component that integrates an accelerometer, gyroscope and barometric pressure sensor, in the same package, said Stéphane Elisabeth, RF and advanced packaging cost engineer at System Plus Consulting, part of Yole Group of Companies. “Innovation clearly is not in the selection of the components, but more in the smart combination of the three devices in the same package.”

InvenSense, which was acquired by TDK, is a leader in inertial measurement unit (IMU) development and was a major supplier to Apple for many years. InvenSense leveraged its pressure sensor technology acquired through the acquisition of Sensirion’s barometric division to develop its own barometric pressure sensor.

“Using single package integration, the U.S. company merged a 6-axis inertial sensor already identified in iPhone 6 with a barometric pressure sensor based on a design coming from the barometric division of Sensirion,” said Elisabeth. “Therefore, InvenSense took the benefits of Sensirion’s partial acquisition, taking place in 2016, by developing a specific approach, eliminating a package and minimizing board area requirements.”

The cost difference between the 6-axis inertial sensor and barometric pressure sensor compared to the 7-axis combo sensor is mostly due to the packaging required for the separate barometric pressure sensor, said Elisabeth. “A standard 6-axis IMU from InvenSense has 3 x 3 x 0.75-mm packaging and a standard barometric pressure sensor has 2 x 2 x 0.72-mm footprint. In comparison, the 7-axis has a 4 x 4 x 1.37-mm packaging.”

In terms of technical benefits, the reduction of the height enables better integration in drone applications, said Elisabeth. The footprint savings also allows for the integration of more functions or a reduction in the PCB cost, he added.

“The selling prices of IMUs have fell in recent years and adding new functions is a way to keep a profitable average selling price,” said Elisabeth.

“Moreover, the integration of the pressure sensor with the IMU in the same packaging gives a better response time in environmental sensing. The pressure change is directly related to the position. Also, the integration of a single digital motion processor (DMP) which combines with the pressure and the 6-axis signal gives more accuracy and better response since the pressure signal isn’t given by a separate device.”

But there are drawbacks. The device requires a specific packaging design; has a higher packaging height due to the integration of the pressure sensor die, and uses proprietary software processing, said Elisabeth.

In addition, it’s a sole-sourced device. But maybe not for long.

“InvenSense’s competitors like STMicroelectronics or Bosch Sensortec already have the technology and the capability to do such a component. In terms of integration, InvenSense has a better form factor,” said Elisabeth. “But in the short term, competitors could be interested in investing in such a development.”

The 7-axis combo sensor primarily targets drone applications as well as other motion tracking devices such as smart watches, wearables, gesture recognition for AR/VR and gaming, and other types of activity monitoring. Yole Développement, a sister company of System Plus Consulting, expects the drone market to reach nearly $3.4 billion in 2023, growing at a compound annual growth rate of 23 percent between 2016 and 2021.

The ICM-20789 7-axis combo sensor is available in volume production. Samples and evaluation boards are available. More information is available in the datasheet and application note.