Sensirion and STMicroelectronics Join Forces To Improve Environmental Sensing

March 16, 2023 by Dale Wilson

Sensirion’s Director of Product Management speaks with All About Circuits about the new partnership between Sensirion and STMicroelectronics to provide improved humidity and temperature sensing systems.

Behind the scenes, this partnership had been brewing for some time. Back in November, STMicroelectronics (ST) quietly released a transition guide encouraging users to transition from their HTS221 capacitive digital sensor for relative humidity and temperature to the Sensirion SHT4x.


Sensirion and STMicro sensing agreement

STMicroelectronics recommends the Sensirion SHT4x for new designs. Image used courtesy of Sensirion


Now, Sensirion has made the partnership official with the announcement that it has joined the ST Partner Program for humidity and temperature sensors. All About Circuit discussed this strategic partnership with Dr. Maximilian Eichberger, Director of Product Management for Humidity and Temperature Sensors at Sensirion.


Powerful Combination of Two Leaders

According to Dr. Eichberger, the partnership agreement began taking shape in the first half of 2022. He views their collaboration as a “really powerful combination of two leaders” that builds off their complementary strengths. 

After years of competition in this portion of the sensor market, they began working together to solve end-customer problems. This included the development of the transition guide to assist designers who were already using the HTS221 sensor (which is no longer recommended for new designs.) Comparing the specifications from their migration guide provides one indication of why STMicroelectronics recognized the value of partnering with Sensirion in this product space. Namely, the Sensirion sensors provide clearly superior performance.


Table 1. Migration guide with specification comparison for humidity and temperature sensor ICs
Parameter STMicro HTS221 Sensirion SHT4x
Dimensions (mm) 2.0 x 2.0 x 0.9 1.5 x 1.5 x 0.5
Package 6-pin HLGA 4-pin DFN
Supply voltage (V) 1.7 - 3.6 1.08 - 3.6
Average current (μA @ 1Hz) 2.0 0.6
Typ. RH accuracy (%RH) ±3.5 to ±5.0 ±1.0 to ±1.8
Typ. T accuracy (°C) ±0.5 to ±1.0 ±0.1 to ±0.2
Response time 63% (s) 10 4
Optional filter membrane No Yes
Optional protective cover No Yes
Integrated heater No Yes


The SHT4x sensors also include an on-chip heater that was unavailable on the STMicroelectronics sensors. The integrated heater can be used to remove solvents or moisture that may collect on the sensors and thereby degrade performance. 

An optional integrated PTFE filter membrane is designed to provide additional protection. The 100 μm thick membrane is specified to filter > 99.99% of particles larger than 200 nm. The flat exterior surface provided by the optional membrane should also help with surface wiping to remove particulates. 


Partnership Yields New Evaluation Kit Using STM32

In our discussion, Eichberger also highlighted a new SENSEVAL-SHT4XV1 evaluation board as a product of the partnership between STMicroelectronics and Sensirion. This eval kit allows easier testing and development of SHT4x applications using ST’s STM32 microcontroller family. The eval board is specifically supported by the STMicroelectronics STEVAL-MKI109V3 motherboard and several of their X-NUCLEO-IKS01Ax expansion boards.


​​Sensirion SHT4x Evaluation Board

This Sensirion evaluation board is for direct integration with STMicroelectronics development tools. Image used courtesy of Sensirion


Eichberger stated that both companies viewed this as a “win” for their customers as, jointly, they can provide a complete, integrated ecosystem of market-leading environmental sensors and a rich selection of microcontrollers and wireless connectivity products. 


Next Up: Improved Sensing of VOCs, CO2, and PM2.5

Eichberger views this announcement as an exciting first step in this new partnership. Sensirion continues to “work closely with STMicroelectronics engineering teams” to improve both time-to-market and performance. 

When asked about interesting new products they are working on, Eichberger highlighted their efforts to continue improving the sensing of volatile organic compounds (VOCs). While Sensirion already has products in this space, VOC sensing is a “complicated topic” as sensors are impacted by “almost everything from smelly cheese to body sprays.” Ideally, they want to be able to isolate these annoying but usually harmless VOCs from more critical compounds. 

Next, he went on to discuss the importance of carbon dioxide (CO2) monitoring for indoor air quality. Getting good data on CO2 concentrations is a “good proxy for human-origin aerosol concentrations which leads to possible virus transmission.”

Finally, sensing fine particulate matter of less than 2.5 μm diameter (known as PM2.5) is another area of focus for Sensirion. These smaller particles may remain suspended in the air for long durations and are considered a potential health risk if they reach the lungs and enter the bloodstream.

The explosion of the Internet of Things (IoT) in both home and industrial settings is rapidly expanding the requirements for distributed sensing and environmental data collection. This new partnership between Sensirion and STMicroelectronics aims to provide new and better solutions to address these and other industry challenges.