Simpler and greener relative humidity measurements

The Si701x/2x family can be used in conjunction with Silicon Labs’ broad portfolio of energy-friendly microcontrollers and wireless ICs to enable best-in-class solutions for measuring, controlling and reporting environmental conditions for a wide range of connected devices linked to the Internet of Things.

Mark Thompson, vice president and general manager of Silicon Labs’ Access, Power and Sensor products, comments: “The new Si701x/2x family represents the state of the art in RH sensing, offering an unmatched combination of ultra-low power, ease of use, small size, precision, reliability and compatibility with standard manufacturing flows. As the only single-chip RH/temperature sensing solutions offered by a broad-based semiconductor supplier, the Si701x/2x sensors can be combined with Silicon Labs’ energy-friendly MCUs, ZigBee and sub-GHz wireless ICs, and other sensor products to address wireless sensing applications for the Internet of Things.”

Combining a standard CMOS mixed-signal IC with a proven technique of measuring humidity using a polymer dielectric film, the Si701x/2x devices provide a superior alternative to legacy RH sensing approaches, which use discrete resistive or capacitive RH sensing elements along with analog circuits for temperature compensation and signal conditioning. Often necessitating a bigger bill of materials and PCB area, these discrete solutions typically have a high risk of contamination and low reliability. Incompatible with surface-mount technology, RH/temperature calibration must be performed during PCB assembly. Attempting to solve these challenges, RH sensor module suppliers have resulted in a higher system cost without improving reliability or risk of contamination.

Contrasting the complex discrete approaches, the monolithic Si701x/2x ICs provide the highest ease of use and reduced manufacturing cost and complexity. Fully calibrated and SMT compatible, the Si701x/2x family achieves highest long-term reliability (thanks to the integrated CMOS design) and also requires negligible BOM cost. Protection against contamination is offered by an optional filter cover, in addition to the factory-installed cover (a Teflon membrane sealed at the top of the IC). This factory-installed cover protects the sensor throughout the device’s entire lifetime, shielding the sensing element from dust, dirt and cleaning agents during operation.

Featuring the lowest power consumption in the integrated RH/temperature sensor market, the Si701x/2x sensors have a 3.3 V power supply voltage and 8-bit resolution, while consuming only 1.9 µW average on-chip power when taking one sample per second. Up to six times lower power than competing RH sensors, this energy efficiency makes the sensors ideally suited for power-sensitive applications and helps extend battery life.

Providing best-in-industry RH sensing precision, the Si701x/2x family is ideal for a majority of RH and temperature sensing applications that have stringent accuracy requirements. Operating over a temperature range from -10°C to +85°C, superior long-term RH accuracy is ensure with the lowest long-term RH drift at <0.25% RH per year. The sensors also maintain ±3% RH maximum accuracy over a wide range of humidity from 0 to 80% RH, and ±0.4 °C maximum temperature accuracy over the operating temperature range.

The industry’s only integrated RH/temperature sensor product that supports a two-zone temperature measurement capability, the Si7013 supports second-zone temperature sensing with programmable linearization in order to remove the necessity of an additional analog-to-digital converter and compensation software in the system. Applications such as thermostats that require a second-zone temperature sensor can now use the Si7013 to efficiently measure the analog voltage of an external thermistor.

Available now in a small-footprint 3 mm x 3 mm QFN package that is pin-compatible with other digital RH sensors available in the market, production quantities of the Si701x/2x sensors start from $2.13 (USD) each in 10,000-unit quantities.