Proving the Business Case for the Internet of Things

Infineon pressure sensor improves accuracy for wearables

Steve Rogerson
March 3, 2015
 
German semiconductor company Infineon Technologies has launched a ±5cm resolution, miniature mems (micro electro mechanical systems) pressure sensor for use in mobile and wearable gadgets and IoT devices. On display at this week’s Mobile World Congress in Barcelona, the DPS310 is a low-power digital barometric pressure sensor that enables the development of navigation, location, well-being, gesture recognition and weather monitoring applications.
 
Delivering accurate and stable performance across a wide temperature range, the device is suitable for indoor navigation and assisted location applications – such as floor detection in shopping malls and parking garages – and outdoor navigation where it can help to improve navigation accuracy or support dead reckoning when a GPS signal is not available.
 
In addition, the ability to provide accurate data for calculating elevation gain and vertical speed suits activity tracking in mobile and wearable health and sports gadgets, while precise pressure measurement opens up possibilities for gesture recognition and the detection of rapid weather changes.
 
The pressure sensor is based on capacitive sensing rather than the piezo-electric principle employed in most other digital pressure sensors. This guarantees high precision across a broad range of temperatures even when temperature changes rapidly. This is clearly an advantage since the temperature inside a mobile device can change quickly due to several heat sources.
 
In high-precision mode, it can measure heights within ±5cm enabling the exact detection of transient states, which are the biggest challenges of indoor navigation. The high resolution could help, for example, in identifying when a person is moving from one floor of a building to another and triggering the download of a new floorplan. High-accuracy height measurement is also required by sports and fitness applications that need to differentiate between the different types of steps a wearer might be taking and the corresponding calorie burn rate.
 
Device size is 2.0 by 2.5 by 1.0mm and in low power mode the current consumption is 3μA at one measurement per second, falling to just less than 1μA in standby mode. An integrated fifo that stores the last 32 measurements helps to reduce overall system power consumption by extending the time that a host processor can remain in sleep mode between sensor readouts.
 
It provides reliable and accurate performance at pressures from 300 to 1200hPa and at temperatures from -40 to +85ËšC. Multiple measurement and resolution modes allow the device to be optimised to the target application. For example, one-time measurement can be configured for GPS altitude accuracy, while the option to take several measurements per second will address the needs of gesture recognition.
 
Each sensor is calibrated individually and has on board the calibration coefficients for accurate compensation of measured pressure and temperature values. Sensor measurement data and calibration coefficients are available through the sensor’s I2C/SPI digital interface.
 
“Pressure sensors are becoming an essential part of mobile and wearable gadgets,” said Roland Helm, segment head for sensors at Infineon. “With regard to IoT, the pressure sensor is also an important building block of integrated consumer sensor solutions. Built on proven semiconductor processes and combining ultra-high-resolution, good temperature stability, low-power operation and miniature package size, the DPS310 enables developers to improve the functionality and enhance the user experience in applications ranging from assisted location and navigation through sport and fitness to real-time weather monitoring.”
 
Engineering samples will be available in May 2015 with volume production planned for the third quarter of this year. Infineon will support design-in with starter kits and evaluation boards. It operates at a supply voltage of 1.7 to 3.6V and is supplied in an eight-pin LGA package.
 
The company also announced at MWC embedded security controllers for premium handsets and smart wearables. The latest members of the Solid Flash-based SLE 97 family provide memory up to 1.5Mbyte in small packages. This can provide the capacity to store biometric data or encryption keys on the security controller for applications such as fingerprint authentication, secured cloud services, NFC-based applications or online payments.