Silicon Labs has introduced a new family of relative humidity (RH) and temperature sensors that simplify RH sensing designs while providing both power efficiency and ease of use. Silicon Labs’ second-generation RH sensing solution, the Si701x/2x sensors combine a standard CMOS mixed-signal IC with a proven technique of measuring humidity using a polymer dielectric film.
The new family is designed to provide accurate RH sensing for home automation, HVAC, refrigeration, healthcare, remote monitoring, automotive and industrial equipment. When combined with Silicon Labs’ broad portfolio of energy efficient microcontrollers and wireless ICs, the Si701x/2x family is suitable for measuring, controlling and reporting environmental conditions for a wide range of connected devices linked to the Internet of Things.
The Si701x/2x sensor family is being described as a significant improvement on legacy RH sensing approaches, which use discrete resistive or capacitive RH sensing elements along with analogue circuits for temperature compensation and signal conditioning.
The Si701x/2x monolithic ICs offer ease of use and reduce both manufacturing cost and complexity. The Si701x/2x family requires negligible BOM cost and is fully calibrated and SMT compatible. The integrated CMOS design provides the highest long-term reliability, and an optional filter cover provides added protection against contamination. The factory-installed cover – a Teflon membrane sealed at the top of the IC – protects the sensor not only during PCB assembly but also throughout the device’s entire lifetime, shielding the sensing element from dust, dirt and cleaning agents during operation.
The Si701x/2x sensors have very low power consumption compared to other devices in the integrated RH/temperature sensor market. With a 3.3 V power supply voltage and 8-bit resolution, the Si701x/2x sensors consume only 1.9 µW average on-chip power when taking one sample per second, which is up to six times lower power than competing RH sensors.
The Si701x/2x sensors maintain ±3% RH maximum accuracy over a wider range of humidity (from 0 to 80% RH) than competing RH/temperature sensors. The sensors also maintain ±0.4 °C maximum temperature accuracy over a wider temperature range (from -10 to +85 °C) than competing devices. In addition, the Si701x/2x family has the lowest long-term RH drift at <0.25% RH per year, ensuring superior long-term RH accuracy.
The Si701x/2x family features the industry’s only integrated RH/temperature sensor product that supports a two-zone temperature measurement capability. The new Si7013 device supports second-zone temperature sensing with programmable linearization, which eliminates the need for an additional analogue-to-digital converter (ADC) 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 analogue voltage of an external thermistor.
According to Mark Thompson, vice president and general manager of Silicon Labs’ Access, Power and Sensor products, “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.”