STMicroelectronics launches innovative infrared sensor to improve presence and movement detection in building automation

Highly integrated, ultra-low power sensor with micromachined thermal transistors replaces traditional passive infrared detectors

July 31, 2023, China – STMicroelectronics (ST;), a world-leading semiconductor company serving multiple electronic applications, released a new human presence and movement detection chip that can improve the traditional use of passive infrared (PIR) sensors. Monitoring performance of sensing technology for security surveillance systems, home automation equipment and IoT devices.

Traditional PIR sensors can only produce a measurable response signal when the object being detected moves. The STHS34PF80 sensor has a built-in thermal transistor, so it can detect stationary objects. In addition, PIR sensors require Fresnel lenses to sense moving objects, while STMicroelectronics' new detector uses a simpler lensless structure.

Simone Ferri, General Manager of STMicroelectronics' AMS MEMS Sub-Products Division, said: "Today's smart homes, smart buildings and the Internet of Things require precise human presence detection capabilities to improve the control capabilities of lighting, heating, security, safety monitoring and other systems to create A sustainable future. ST’s new STHS34PF80 is an affordable, ultra-low-power sensor that ensures consistent, uninterrupted operation of building automation systems regardless of whether the person being detected is moving within the building. In addition, this new product innovatively integrates CMOS chip manufacturing technology, silicon micromachining technology and low-voltage circuit design capabilities.”

STHS34PF80 embeds intelligent algorithms for human presence and movement detection, targeting applications such as alarm security systems, home automation, smart lighting, IoT devices, smart lockers and smart video intercom systems. The lensless four-meter detection distance and 80° field of view can cover most of the area in front of the sensor. The operating current is 10µA, the power consumption is lower than traditional PIR, and it is packaged in 3.2mm x 4.2mm x 1.455mm. It has a compact structure and is suitable for high-speed assembly in automated production lines. The sensor is highly resistant to direct light interference and electromagnetic interference (EMI).

The sensor evaluation board STEVAL-MKI231KA provided by ST can help users simplify the test and development process of STHS34PF80. Developers only need to plug this daughterboard into the X-NUCLEO-IKS01A3 or STEVAL-MKI109V3 motherboard, and then use STMicroelectronics' Unico-GUI graphical interface software to configure the infrared sensor and start a simplified measurement process. . The driver for the STHS34PF80 can be found on GitHub. In addition, the X-CUBE-MEMS1 software package includes a ready-made software library for compensation, detection of human or object presence. Users can quickly run a simple application, measure with the STHS34PF80, test the results, and then start creating a new application.

Detailed technical information

The STHS34PF80 uses STMicroelectronics' mature and reliable silicon-on-insulator (SOI) CMOS technology to efficiently integrate thermal MOSFET (TMOS) transistors and digital readout circuits on the same chip . TMOS thermal devices are sensitive to the heating effect of infrared radiation incident on the transistor gate. The SOI architecture uses STMicroelectronics' mature MEMS (microelectromechanical systems) process to simplify the micromachining process and thermally isolate TMOS transistors to ensure the accuracy of temperature sensing.

The supply voltage of TMOS is lower than the threshold voltage required to fully conduct the transistor. In this subthreshold state, the drain-source current is highly temperature dependent and can respond to very low infrared radiation to produce a voltage signal that can be accurately measured. This physical property enables the sensor to detect the presence of a person through infrared radiation, regardless of whether the person is moving or stationary.

Another benefit of the sub-threshold operating mode is that the transistor power consumption is very low, and the battery life of the STHS34PF80-based sensor is longer, so fewer recharges or batteries are required. In addition, standard CMOS manufacturing technology ensures wafer cost-effectiveness and yield, while utilizing submicron transistors can reduce sensor size. This is different from PIR sensors, whose sensitivity may depend on the size of the pyroelectric pixels. In addition, the on-chip integrated digital interface can be directly connected to the host without the need for additional analog front-end circuits.

The STHS34PF80 is now in volume production and available in a 10-pin grid array (LGA) package.