A Look at InvenSense’s Low-Noise, Low-Power, Waterproof MEMS Capacitive Barometric Pressure Sensor

A new MEMS capacitive barometric pressure sensor, from InvenSense, is said to be the industry's lowest-noise and lowest-power pressure sensor.

InvenSense has released the ICP-101xx series of high-accuracy, low-power, waterproof barometric pressure sensors. Keep in mind, however, that while this family of pressure sensors includes four ICs—each with its own part number—only two of the four sensors are indeed waterproof.

By the way, is anything in this world really waterproof besides rubber? The touted waterproof rating of these two parts, specifically the ICP-10100 and ICP-10110, is IPx8, which is called out in the figure below as being waterproof to 1.5 m. And Section 1.2 (entitled Product Overview) clarifies that these ICs are only waterproof at 1.5 m for 30 minutes.

 

Only two of the four ICs in the ICP-101xx series are waterproof. Table taken from the datasheet (PDF).

 

Still, I think it's quite impressive that these ICs are waterproof to any degree, considering the three holes in the lid (see the figure below).

 

The ICP-101xx series has two package types; only the three-hole version is waterproof. Image taken from the datasheet (PDF).

Key Features

Only years ago, actually closer to a decade now, I was intimately involved in designing systems that required pressure sensors. And although every system has its own requirements, the pressure sensors I used back then were big, bulky, and not nearly as impressive as this series of pressure sensors. And when I say impressive, I'm referring to their very small package sizes (see the images above), their low current consumption, and, of course, their ability to achieve, according to the press release, "the industry’s lowest pressure noise of 0.4 Pa RMS."

And kudos to InvenSense for their transparency regarding the "industry’s lowest pressure noise" claim: as called out in the press release, this claim is based on their "January 2018 InvenSense market research."

Other key features of this pressure sensor series include the following:

• an impressive relative accuracy of ±1 Pa, which equates to less than 5 cm (according to the press release) or 8.5 cm (according to the datasheet...perhaps InvenSense should revisit these two sources of information to ensure they are consistent with regard to the sensor’s specs)
• current consumption of 1.3 µA
• an operating temperature range of -40° to 85°C

However, we need to be mindful of trade-offs. For instance, the table below shows us that a designer cannot achieve both 1.3 µA of current consumption and 0.4 Pa of noise.

 

In the context of integrated circuits, lower power generally corresponds to higher noise, and this is exactly what we observe in the ICP-101xx datasheet.

 

Another trade-off is related to the IC's operating temperature range and its operating pressure range. In the Operation Ranges section (Section 2.1), InvenSense informs us that these sensors demonstrate their "best performance" when operated within the "recommended temperature and pressure range" of 0 to 45°C and 95 to 105 kPa (aka the "normal" range). The table below defines the three operation ranges.

 

Operation ranges, from the datasheet.

Guidance and Tips for Using This Sensor

InvenSense has provided guidelines and tips for implementing this sensor series. For example, they recommend that strong light sources be avoided if optimal operation is desired, because "injected photo current" resulting from these light sources can influence the sensor's performance.

Other helpful information has been provided via the typical application circuits, which are located in the Typical Operating Circuit section (Section 4.3) of the datasheet. The two figures below depict application circuits for each of the two package types. InvenSense recommends that the "power supply pins" be decoupled with a 100 nF capacitor, and this (along with the portion of the sentence underlined in red in the diagram below) gives the impression that the VDD pin and the ground pin should have a decoupling cap, but this is undoubtedly a case of imprecise language (as confirmed by the circuit diagrams, which have only one decoupling cap, as expected). Nothing will be gained by connecting a capacitor between ground and ground.

 

Application circuit for the parts with the 2 × 2 × 0.72 mm LGA package, from the datasheet.

 

Application circuit for the parts with the 2 × 2.5 × 0.92 mm LGA package, from the datasheet.

 

Have you had a chance to use one of the sensors from the ICP-101xx family? If so, leave a comment and tell us what you think.