Silicon Pressure Sensor Uses MEMS Technology to Provide High -Resolution Measurements

Thanks to innovative micro-electro-mechanical systems-based silicon pressure sensor from STMicroelectronics (News - Alert), portable devices will soon be able to pinpoint their height variation relative to sea level to better than one meter.

STMicroelectronics’s new LPS001WP is a tiny silicon pressure sensor that uses novel MEMS technology to provide extremely high resolution measurements of pressure and, therefore, altitude. It comes in an ultra-compact and thin package suitable for use in smartphones, sports watches, and other portable equipment, as well as in weather stations and automotive and industrial applications.

In a statement, Benedetto Vigna, general manager of MEMS, Sensors and High-Performance Analog Division, STMicroelectronics, said, "MEMS technology is allowing us to continually develop new sensors that can measure physical parameters such as linear or angular motion, pressure, or magnetic fields at ever-decreasing cost and increasing accuracy."

One of the first expected applications is the enhancement of portable devices equipped with traditional GPS functions that can only identify the location of the device in two dimensions. With the addition of the LPS001WP, the same devices would be able to identify the precise location in all three dimensions, allowing, for example, a mobile phone to send a call to an emergency fire, medical or police service that identified not only the location of the building but also the particular floor, said STMicroelectronics.

The LPS001WP has an operating pressure range of 300 to 1,100 millibar, corresponding to the atmospheric pressures between -750 and +9000 m relative to sea level, and can detect pressure changes as small as 0.065 millibar, corresponding to 80 cm of altitude. The device is fabricated using a proprietary technology, called "VENSENS," that allows the pressure sensor to be fabricated on a monolithic silicon chip, the manufacturer said. Also, added ST, manufacturing the device in this way eliminates wafer-to-wafer bonding and maximizes reliability.

The pressure sensor in the LPS001WP is based on a flexible silicon membrane formed above an air cavity with a controlled gap and defined pressure. The membrane is very small compared to traditional silicon micro-machined membranes and is protected from breakage by built-in mechanical stoppers. The membrane includes a piezoresistor, a tiny structure whose electrical resistance varies as the membrane flexes in response to changes in the external pressure. The change in resistance is monitored, thermally compensated, and converted to a digital value that can be read by the equipment's host processor using the industry-standard I2C or SPI communications protocols, noted ST.

Housed in a small plastic land-grid-array (HCLGA-8L) package, the new MEMS based pressure sensor will be available next month at a typical price of $2.80, in quantities of 1000 units, according to ST.