STMicroelectronics enables precision 3D location sensing


Small digital pressure sensor uses MEMS technology to precisely measure altitude

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ST's new pressure sensor can accurately measure air pressure from 260 millibars (about 10 km elevation) to 1,260 millibars (about 1800 m below sea level).

STMicroelectronics has introduced a new pressure sensor that allows mobile phones and other portable devices to calculate their vertical elevation relative to sea level with very high accuracy. This means that the mobile device will know not only on which floor of a building it is located, but almost on which step of the staircase. Accurate location of mobile devices will be the key enabler for many emerging LBSs (location-based services), which are widely expected to be the next wave of "killer applications" in the mobile world. The challenge is to provide the means of identifying the location of the mobile device in three dimensions in a way that meets a variety of conflicting constraints including spatial resolution, reliability, physical size, robustness, and cost. For the horizontal part of the location (latitude and longitude), the universally adopted method uses the GNSS (global navigation satellite system) and can calculate the horizontal position of the device to within a meter in optimum conditions where the device can receive signals from four or more satellites. ST has already demonstrated a method for indoor navigation developed in conjunction with CSR that can locate devices horizontally and vertically, even in the absence of any satellite signals. For the third dimension (vertical elevation), atmospheric pressure can provide greater resolution than GNSS, especially when fewer than four satellite signals are visible, as pressure drops steadily with increased elevation. ST's new pressure sensor can accurately measure air pressure from 260 millibars, which is the typical air pressure at a height of around 10 km (about 1,500 m higher than the summit of Mount Everest) to 1,260 millibars, which is the typical air pressure at 1,800 m below sea level, about half the depth of the deepest mine ever dug. Housed in a tiny 3 x 3mm package and offering low-voltage operation and ultra-low power consumption, the new device is well suited for use in smart phones, sports watches, and other portable equipment, as well as in weather stations and automotive and industrial applications. Samsung has already adopted the LPS331AP for use in its latest and most advanced smartphone. Technical features of the LPS331AP

  • High resolution, low-noise sensor able to detect differences within centimeters of altitude variation
  • Selectable output data rate from 1 to 25 Hz
  • Low power consumption: low res. mode 5.5 μA, high res. mode: 30 μA
  • Supply voltage: 1.71 to 3.6 V
  • Temperature range: -40 to +85 °C
  • Integrated temperature sensor enabling temperature span compensation
  • Fab calibration of pressures and temperatures, eliminating the need for in-house calibration of shipped devices
  • Supplied in a 3 x 3 x 1mm plastic land-grid-array (HCLGA-16L) package. The package is holed to allow external pressure to reach the sensing element.
The LPS331AP is now in volume production at a typical price of $2.60 in quantities of 1,000 units. Samples and evaluation kits are available to support design-in and shorten time-to-market. ST's pressure-sensor evaluation kit consists of a motherboard (STEVAL-MKI109V2) and a plug-in module, the STEVALMKI120V1 adapter including the LPS331AP pressure sensor. STMicroelectronics Product deeplink