ST Highlights New Temperature Sensors’ Accuracy—to Within 0.25°C

November 19, 2019 by Gary Elinoff

The STTS22H from STMicroelectronics typically draws 0.5 µA in standby mode.

STMicroelectronics' new bandgap temperature sensor, the STTS22H, is packaged with an A/D converter, signal processing logic, and an I²C/SMBus 3.0 interface.


The STTS22H. Image from STMicroelectronics


The device supports temperature and heat-flow monitoring in HVAC systems, air humidifiers, and refrigerators. It is also applicable in building-automation systems, shipping-container loggers, asset trackers, and smart consumer devices where conserving power is a prime design criterion.


Multiple Operating Modes

The STTS22H is compliant with the industry-standard SMBus 3.0 and I2C buses. When the sensor operates in an SMBus slave mode, an interrupt pin can support the SMBus Alert Response Address (ARA). This mode allows the device to signal the application if the temperature falls outside of the user-defined threshold of upper and lower limits.

Other operating modes include a configurable output data rate (ODR) down to 1Hz and a power-saving, one-shot mode. In addition, programmable I²C/SMBus slave addresses allow two STTS22H sensors to share the same bus.


Low Power Consumption 

Power efficiency is a prime feature of the STTS22H with the unit drawing 2.0 µA at 1 Hz ODR and 1.75 µA during periodic one-shot measurements. Additionally, the 1.5V–3.6V operating voltage range allows the unit to operate directly from typical lithium-ion batteries without requiring boost conversion. 

The full operating range is from -40°C to +125°C. Factory calibration enables the STTS22H to maintain its 0.25°C typical accuracy from ±10°C to ±60°C, with no need for the user to do any calibration.


Maximum and minimum temperatures for STTS22H

Maximum and minimum temperature accuracy of STTS22H. Image from STMicroelectronics

Conversion times are 5ms for a 16-bit temperature reading. The package features an exposed pad, which allows thermal relief for the device to maintain a low-temperature differential.


Applications for the STTS22H

ST foresees that the STTS22H will be applicable in a range of home consumer goods, including thermostats, smart home automation, air humidifiers, refrigerators, other white goods, and HVAC systems. The digital temperature sensor can also be used in wearable devices, smartphones, portable consumer devices, and assets and goods tracking. 

The STTS22H is RoHS, ECOPACK, and “Green” compliant, and is available in a 2.0  x 2.0 x 0.5mm, 6-lead UDFN package.


The STEVAL-MKI200V1K Evaluation Kit 

The STEVAL-MKI200V1K evaluation kit includes a probe with an STTS22H temperature sensor that connects through a cable to the STEVAL-MKIGIBV1 adapter board.


STEVAL-MKI200V1K Evaluation Kit 

STEVAL-MKI200V1K evaluation kit. Image from STMicroelectronics

The adapter can then interface to the STEVAL-MKI109V3 motherboard, which is a development platform, allows engineers to monitor the behavior of ST sensors.


STEVAL-MKI200V1K circuit schematic

STEVAL-MKI200V1K circuit schematic. Image from STMicroelectronics

Around the Industry

The TMP117 from Texas Instruments has an operating range of -55°C to +150°C with an accuracy of ±0.3°C over the whole range. The accuracy from -20 to +50°C is ±0.1 °C.

Power consumption is 150 nA in shutdown mode. A medical-grade device, the TMP117 meets ISO 80601-2-56 and ASTM E1112.

Silicon Labs’ Si705x digital temperature sensor family features a band-gap temperature sensor element and an analog-to-digital converter with up to 14-bit resolution. Communication occurs using an I2C interface.

Members of the series feature accuracies ranging from ±0.1°C to ±1.0°C over an operating range of -40°C to +125°C.