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Emerald Group Publishing Limited
Copyright © 2013, Emerald Group Publishing Limited
Silicon Labs introduces single-chip relative humidity sensor
Article Type: New products From: Sensor Review, Volume 33, Issue 2
Silicon Laboratories, Inc. a leader in high-performance, analog-intensive, mixed-signal ICs, has introduced a digital relative humidity (RH) and temperature “sensor-on-a-chip” solution. The new Si7005 sensor advances the state of the art in RH sensing by combining a mixed-signal IC manufactured on standard CMOS with a proven technique of measuring humidity using a polymer dielectric film. The Si7005 sensor is ideal for applications that monitor or control humidity and temperature including automotive climate control and defogging, HVAC, refrigeration, weather stations, food processing, printers, asset tracking, and medical instruments such as nebulizers, oxygen concentrators and respiratory therapy equipment.
Traditional approaches to RH sensing use discrete resistive and capacitive sensors, hybrids and multi-chip modules (MCMs). These legacy approaches suffer from high bill of materials (BOM) cost and component count, large footprints, manufacturing challenges and the need for labor-intensive customer calibration. In contrast, the single-chip Si7005 humidity sensor is smaller, more reliable, and much easier to design in and use than traditional discrete/module solutions.
The Si7005 humidity sensor is a “plug-and-play,” factory-calibrated RH and temperature sensing solution. The device’s digital output and factory calibration frees the developer from having to calibrate the sensor and also makes Si7005 sensors completely interchangeable. No software/firmware update or recalibration effort is required to change from one sensing unit to another. The customer spends no time or labor on the manufacturing line adjusting each unit, which eases production, rework and field servicing. The Si7005 sensor’s compact QFN package supports tape-and-reel packaging, automated pick-and-place PCB manufacturing and conventional soldering processes, further helping OEMs reduce manufacturing costs.
The Si7005 sensor uses state-of-the-art sensing technologies to enable precise monolithic humidity and temperature sensing. Temperature is sensed by a precision band-gap referenced circuit on the die. Humidity is sensed by measuring the capacitance change of an industry-standard low-k dielectric layer applied to the surface of the die. Both temperature and humidity are precisely measured in very close proximity on the same monolithic device, providing exceptional measurement accuracy. The Si7005 device also is the lowest power RH sensor of its kind, consuming only 2 μA on average at one measurement per minute, which makes it ideal for battery-powered applications.
Figure 2 Silicons Lab’s Si7005 RH and temperature sensor
The entire BOM for the Si7005 RH sensor solution is just two bypass capacitors versus the dozens of components often required to implement the same functionality with a discrete solution. The Si7005 device integrates sensing elements, an analog-to-digital converter (ADC), signal processing, non-volatile memory for calibration data and an I2C interface in a monolithic CMOS IC. This high level of single-chip integration makes the sensor rugged and reliable, reduces cost and development time, and simplifies board design (Figure 2).
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