Meeting IoT-Era Demands
Although sensors have always played a key role in embedded systems, the IoT phenomenon has pushed sensor technology to the forefront. Sensor vendors are meeting the demand for ever greater performance and precision.
Like the senses of the human body, sensors do the critical work of interfacing embedded systems with the real analog world. Sensors span a wide variety of sensor types and functions including: temperature, pressure, motion, imaging and more. To meet the demands for high-performance, higher precision and integrated solutions, sensor manufacturers continue to up their game. Factoring in the proliferation of IoT and intelligent edge applications, sensors are now moving to smaller, low-power designs to meet the new requirements of those systems.
As the Internet-of-Things (IoT) phenomenon kicks into high gear, sensor innovations have had to keep pace. As result, manufacturers of sensors and sensor interface devices have been hard at work developing highly integrated, high-performance devices.
It’s no surprise that microcontroller (MCU) and analog IC vendors have led many of the sensor technology and product developments over the past 12 months. Those vendors are used to working closely with the analog world. Sensors comprise a topic too wide for one article, so this is an overview of the latest developments in temperature sensors, MEMS (Micro-Electro-Mechanical Systems) accelerometer sensors, pressure sensors, image sensors and more.
MULTI-FUNCTION SENSOR
There’s no doubt that sensors are getting more sophisticated and intelligent. For example, in April, ACEINNA announced high volume availability of its new IMU383ZA device. The IMU383ZA integrates triple-redundant, 3-axis MEMS accelerometer and gyroscope sensors (Figure 1). This miniature module is factory-calibrated over the -40°C to +85°C industrial temperature range, to provide consistent performance through extreme operating environments for a wide variety of applications including automotive ADAS, autonomous systems, drones, robotics, agricultural, construction and other industrial machines.
The IMU383ZA offers improved performance (1.3 deg/hr, 0.08 deg/root-hr), in addition to a unique fault-tolerant sensor architecture for improved reliability. The IMU383ZA provides a standard SPI bus for cost-effective board-to-board communications. Other critical new features include advanced synchronization and a bootloader for field upgradeability. The tiny devices measure only 24mm × 37mm × 9.5mm. The IMU383ZA is an improved, pin-compatible version of ACEINNA’s IMU381ZA.
The IMU383ZA triple-redundant sensor architecture consists of three independent, 3-axis accelerometer and 3-axis gyros for excellent accuracy and reliability. By embedding a triple-redundant sensor array, the IMU383ZA uses ACEINNA’s proprietary voting scheme to utilize only valid sensor data. Any defective sensor output or errant dataset will be ignored or de-rated in importance.
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6-AXIS MOTION SENSOR
Applications such as robotics, wearable devices and drones are quite demanding when it comes to high-precision motion sensing. System developers want best-in-class gyroscope stability vs. time and temperature, coupled with rapid real-time response and content synchronization. Aiming to meet such needs, in May TDK announced its InvenSense ICM-42688-P high-performance motion sensor, a 6-axis MEMS motion tracking device that combines a 3-axis gyroscope and a 3-axis accelerometer in a 2.5mm × 3mm × 0.9mm package (Figure 2).
Compared to traditional consumer-grade IMUs, the ICM-42688-P provides a 40% lower noise-figure and improves temperature stability by 2x, ensuring any motion event is measured with the highest accuracy, independent of temperature changes, says TDK. The ICM-42688-P also includes two key innovations not available in any other consumer-grade IMU: a 100% accurate clock that eliminates timing errors and a high-resolution analog-to-digital converter.
The converter enables an 8x increase in gyroscope resolution and a 4x increase in accelerometer resolution. Other features include the InvenSense on-chip APEX Motion Processing Engine for gesture recognition, activity classification, and pedometer, along with programmable digital filters, and an embedded temperature sensor. A comprehensive development platform, the DK-42688-P, along with necessary software is available to enable quick-to-market development of customer systems. The InvenSense ICM-42688-P and DK-42688-P developer kit are available from multiple distributors.
TEMPERATURE SENSOR FOR DRAM
Extreme temperatures can seriously affect the performance of sensitive components in computing systems, like memory ICs, for example. With that in mind, in March, Renesas Electronics announced a new precision temperature sensor, the TS5111, targeting DDR5 memory modules as well as a host of other applications such as solid-state disks (SSDs), computing motherboards, and communications equipment that require accurate, real-time temperature monitoring. The new JEDEC-compliant temperature sensor enables memory modules and other temperature-sensitive systems to run at peak efficiency and reliability with real-time, closed-loop thermal management algorithms.
The TS5111 plays a critical role in providing accurate, high-precision system temperatures with programmable warning flags that enable systems to exercise thermal control loop mechanisms such as memory refresh rates, fan speeds and bandwidth throttling. Measuring a mere 0.8mm × 1.3mm, the TS5111 is well suited for small form factor systems as well as applications such as memory and storage modules where proximity sensing is critical for reliable operation (Figure 3). The TS5111 supports I²C, SMBUS, as well as the new I3C Basic protocol for data rates up to 12.5MHz and other advanced features like in-band interrupts, parity check and packet error checks.
Renesas says the device is the first JEDEC-compliant thermal sensor device for DDR5. The company hopes the TS5111 has the potential to coalesce the entire computing industry around a single thermal sensor solution that supports the latest high-speed control bus interface and complies with an industry standard specification. The TS5111 joins a complete family of Renesas’ DDR5 solutions that enable system developers to craft DDR5 DIMM solutions. The current Renesas DDR5 RDIMM ICs include the registered clock driver 5RCD0148HC1, power management IC P8900 and SPD Hub SPD5118. The TS5111-Z1AHRI8 temperature sensor available in a 6-ball WLCSP package.
LINEAR TEMPERATURE SENSORS
Thermistors, although relatively simple devices, are one of the most accurate types of temperature sensors. But not all thermistors are created equal. According to Texas Instruments (TI), negative temperature coefficient (NTC) thermistors are widely used due to their low price. But they present several challenges to design engineers, including degraded performance at temperature extremes and complex calibration requirements, which increases design time.
In February, TI expanded its temperature sensing portfolio to include linear thermistors that deliver up to 50% higher accuracy than NTC thermistors (Figure 4). The higher accuracy of TI’s thermistors enables operation closer to the thermal limits of the other components and the overall system, helping engineers maximize performance while reducing bill-of-materials (BOM) and total solution costs.
TI’s new thermistors deliver reliable, highly accurate thermal measurements, particularly at temperatures above 80°C. This is especially important for industrial, automotive and consumer applications where precise, real-time temperature readings are fundamental to system performance and protection.
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TI’s thermistors also offer very low typical drift of 0.5% to improve the reliability of temperature measurements, enabling designers to boost system performance while maintaining safe operation. Engineers can use TI’s thermistor design tool, available on the thermistor product pages and datasheets on TI.com, to quickly and easily calculate temperature resistance values and kick-start their design with example conversion methods and code. TI’s new thermistor portfolio, which includes the TMP61, TMP63 and TMP64, are offered in through-hole packaging and surface-mount 0402 and 0603 footprint options.
MEMS PRESSURE SENSORS
While they may seem simple at first glance, pressure sensors require some complex trade-offs, balancing precision, response times and an ability to support wide ranges of pressure. For its part, Bourns met those challenges with its four new model families added to the Bourns Precision Sensor (BPS) line in February.
Based on state-of-the-art MEMS technology, the four new BPS310, BPS320, BPS330 and BPS340 series are cost-effective pressure sensor solutions that feature ultra-fast response times, high resolution and long-term stability (Figure 5). These features, along with the ability to work with pressure ranges from 5psi to 500psi, make Bourns’ latest BPS sensors well suited for a vast array of packaging requirements and applications, including industrial systems and low/medium risk medical devices.
The Model BPS310 series is designed to provide high sensitivity/accuracy for ultra-low pressures. For gauge and pressure measurement, the Model BPS320 series offers a robust configuration in a surface mount package. The Model BPS330 series is a through-hole pressure sensor with an aluminum port for low pressure applications with an operating range up to 125°C. With an ability to handle certain harsh medias, the Model BPS340 series is offered in a surface mount package capable of supporting pressure ranges up to 500psi.
MACHINE LEARNING CORE
The more pre-processing that a smart sensor can do, the more it can off-load duties from the MCU to which it’s attached. Exemplifying that concept, in March, STMicroelectronics (ST) launched its latest ISM330DHCX and LSM6DSRX 6-axis iNEMO inertial measurement units (IMU). The new sensors extend the benefits of ST’s motion-detection machine-learning core (MLC) technologies into industrial and high-end consumer applications. The MLC performs basic AI pre-processing of motion data using about 0.001 times the power a typical MCU would consume to complete the same task (Figure 6). As a result, IMUs featuring this IP can offload the host MCU, enabling longer battery runtime, lower maintenance and reduced size and weight in context-aware and motion-sensing devices.
Following the launch of the first MLC-enhanced commercial IMU last year, ST’s LSM6DSRX and ISM330DHCX are well suited for high-end consumer and industrial applications such as augmented/virtual reality, drone flight controls, dead-reckoning navigation systems, disk-antenna positioning systems, fleet management, container-tracking devices and dynamic inclinometers for industrial vehicles.
The consumer-grade LSM6DSRX contains a 3-axis accelerometer and a 3-axis digital gyroscope with extended full-scale angular-rate range up to ±4000dps and leading-edge performance in temperature and time. The industrial-grade ISM330DHCX comes with 10-year product-longevity assurance and is specified from -40°C to 105°C, with embedded temperature compensation for superior stability.
In each device, the MLC interacts with integrated finite-state machine (FSM) logic, which can run simple repetitive algorithms like counting steps, hits or rotations at lower power than is possible in an MCU. The FSM signals to the main controller after detecting a preset number of events or after a defined time has elapsed. Both devices are in production now. The ISM330DHCX is available as a 14-lead plastic land grid array (LGA) device.
SENSOR-LEVEL SECURITY
It might seem odd to think of security as an issue at the sensor level. But when it comes to data-driven supply chains, the issue is real. According to Infineon Technologies, industrial supply chain solutions like digital twins, usage-based pricing models, product warranties or licensing solutions increasingly require reliable and auditable sensor and process data. Yet security is paramount, especially when data is transferred from one company or organization to another.
In an example along those lines, Tributech Solutions takes cross-company data sharing to a new level. To provide an advanced, tamper-resistant data security layer, the Austrian technology company chose the OPTIGA Trust M security solution from Infineon Technologies. Tributech’s DataSpace Agent combines hardware-based security and blockchain technology to securely share and track sensor and process data. Different options for the integration and a very low footprint in terms of memory- and computation-resources allow the integration of the DataSpace Agent at nearly every type of data source, from sensors with low level MCUs to powerful edge devices.
Inside Tributech’s DataSpace Agent, Infineon’s OPTIGA Trust M single-chip solution acts as a highly secured vault for sensitive authentication and cryptographic keys (Figure 7). In addition, the OPTIGA Trust M also provides the cryptographic hashing and signing operations to enable the auditability of sensor data by a hardware-based root-of-trust.
REFLECTIVE SENSOR
Industrial applications often require flexible customized sensor solutions in order to accommodate the dynamic needs of each environment. With that in mind, in September, TT Electronics, announced its OPB9001 PCB module for industrial and medical applications. The OPB9001 module includes the OPB9000 reflective sensor and eliminates the need for peripheral circuitry like resistors, regulators and capacitors because such functionality is integrated into its small, robust package (Figure 8).
According to the company, the OPB9001 product family is capable of directly accepting higher input voltage and can be customized to maximize flexibility and compatibility, even in the most robust and demanding industrial use cases. This reflective sensor can detect objects as far away as 50mm using standard 90% reflective material as well as objects as small as 2.5mm depending on the object distance.
The OPB9001 can also be programmed to recognize various distances within its reflective range. All analog signal conditions are incorporated into OPB9001’s integrated OPB9000 IC and PCB assembly. In addition, the OPB9001 is easily mounted on PCBs and panels, and equipped with an integrated connector.
HIGH-SPEED IMAGE SENSOR
Advances in image sensors continue to progress, moving to even higher frame rates and added functionality. For its latest offering, in September, ON Semiconductor introduced its ARX3A0 digital image sensor with 0.3 Mega-Pixel (MP) resolution in a 1:1 aspect ratio (Figure 9). With up to 360 frames per second (fps) capture rate, it can perform like a global shutter in many conditions but with the size, performance and responsivity benefits of a Back-Side Illuminated (BSI) rolling shutter sensor.
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With its small size, square format and high frame rate, ARX3A0 is particularly suitable for emerging machine vision, AI and AR/VR applications, as well as small supplemental security cameras. Power is becoming increasingly important for many applications that provide still or streaming images. The ARX3A0 is designed to deliver flexible, high-performance image capture with minimal power. It consumes less than 19mW when capturing images at 30fps, and just 2.5mW when capturing 1fps.
The 1/10in.2 format enables low height modules, while the miniature 3.5mm die size helps maximize the sensor’s field of view. Its small size and square format mean the ARX3A0 can be used in emerging applications where orientation isn’t fixed but space is limited, such as AR/VR goggles to monitor the wearer’s eye movement. Eye movement data can be used to adjust the image viewed, which is believed to mitigate the possible effect of motion sickness as experienced by some users. Simultaneous Localization and Mapping (SLAM) is another application where ARX3A0’s small size and low power image sensors will be crucial. 
RESOURCES
ACEINNA | www.aceinna.com
Bourns | www.bourns.com
Infineon Technologies | www.infineon.com
Maxim Integrated | www.maximintegrated.com
ON Semiconductor | www.onsemi.com
Renesas Electronics | www.renesas.com
STMicroelectronics | www.st.com
TDK InvenSense | www.invensense.tdk.com
Texas Instruments | www.ti.com
TT Electronics | www.ttelectronics.com
Tributech | www.tributech.io
PUBLISHED IN CIRCUIT CELLAR MAGAZINE • JUNE 2020 #359 – Get a PDF of the issue
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Jeff served as Editor-in-Chief for both LinuxGizmos.com and its sister publication, Circuit Cellar magazine 6/2017—3/2022. In nearly three decades of covering the embedded electronics and computing industry, Jeff has also held senior editorial positions at EE Times, Computer Design, Electronic Design, Embedded Systems Development, and COTS Journal. His knowledge spans a broad range of electronics and computing topics, including CPUs, MCUs, memory, storage, graphics, power supplies, software development, and real-time OSes.
