Sensors Expo: From Wireless Sensor Networking To Digital Temperature Sensors

While wireless sensor networking, energy harvesting, and MEMS technologies – all having a certain “wow” factor – may have garnered the greatest attention at the recent Sensors Expo trade show, you shouldn’t minimize the importance of more commodity-like – but much needed – components such as digital temperature sensors.

Temperature sensing is becoming even more critical as designers try to cram as many components as possible onto their boards, which typically leads to higher heat generation and thus, the need for much improved temperature monitoring and management.

As a result, when it comes to temperature sensors for mobile devices – or any applications for that matter – designers are looking to achieve lower power, smaller size, and higher accuracy.

While smaller size and lower power requirements are self-explanatory, what is so important about higher accuracy? Well, according to Analog Devices (ADI), higher accuracy eliminates the need to average results, delivers faster data measurement, and improves energy efficiency and reliability.

For designers looking for extremely high accuracy, ADI has developed two digital temperature sensors that achieve a ±25 °C accuracy over a wide temperature range of -20 ° to +105 °C. ADI says these fully calibrated, 16-bit resolution temperature sensors can “cost-effectively” replace thermistors and resistance temperature detectors.

In addition, the high-precision, low-drift ADT7420 and ADT7320 devices offer ±0.5 °C accuracy over a -40 ° to +125 °C temperature range.



Unlike some alternative solutions, these devices are plug-in ready and require no additional signal conditioning or calibration, said ADI. The devices are available with either I²C (ADT7420) or SPI (ADT7320) digital interfaces, which allow system designers to easily integrate them into any number of applications, including data acquisition, optical communications, environmental control systems, medical equipment, or food and pharmaceutical temperature monitors.

These sensors also include a low-power 1-sample/(s) mode that draws only 46 μA typ at 3.3 volts. They also offer a shutdown mode that reduces supply current to just 2 μA. Additional programmable options include over/under-temperature and critical temperature indicators. Both devices are sampling now.

Not to be outdone, STMicroelectronics’ new STTS751, also unveiled at the tradeshow, delivers on all accounts – small size, low power, and high accuracy.



This miniature digital temp sensor, measuring 2 mm x 2 mm, is smaller than ST’s previous product family, and it offers an ultra-low 50 μA operating current, a power-saving 3 μA standby current, and a “one-shot mode” that makes the device well-suited for battery powered devices. ST says the one-shot operation allows the sensor to sleep for extended periods, waking only to provide an instantaneous reading when triggered by the system.

Since heat in any end product can result in poor reliability and/or product failure, having the ability to accurately monitor and manage a system’s temperature is key to any system design.

The STTS751 is mounted on the circuit board to feedback accurate temperature data via a system management bus (SMBus) interface. Similar to ADI’s device, this industry-standard interface means the sensor can easily be designed into a wide range of consumer and professional equipment, including solid state drives, large display backlights, smart batteries, servers and routers, telecom and Internet infrastructure, and e-readers.

The STTS751 is available now in a 6-pin, 2 mm x 2 mm UDFN-6L leadless package or a leaded SOT23-6L package.