Ultra Small, High Accuracy Sensors Target Medical Wearables

Maxim Integrated Products has announced a pair of sensors. The MAX30208 is a clinical-grade digital temperature sensor that enables new wearable health and fitness use cases at half the power. And the MAXM86161 Is an in-ear heart-rate monitor provides best-in-class SNR at lowest power and 40% less space for continuous heart-rate and SpO2 measurements, according to Maxim.

To provide value, wearable health and fitness monitors require greater accuracy in measuring human biometrics such as body temperature and heart rate, but device designers have been limited by sensor accuracy for small, battery-powered, body-worn devices. Maxim’s two new continuous-monitoring body sensors provide higher degrees of accuracy in measuring vital signs such as temperature, heart rate and blood-oxygen saturation (SpO2).

The MAXM86161 in-ear heart-rate monitor and pulse oximeter is the market’s smallest fully integrated solution that delivers highly accurate heart-rate and SpO2 measurements from hearables and other wearable applications. It is optimized for in-ear applications with its industry-leading small package size (40 percent less than the closest competitor) and best-in-class SNR (3dB improvement with band limiting signal for PPG use cases compared to closest competitor). This enables development of devices that cover a wider range of use cases. MAXM86161 delivers approximately 35 percent lower power to extend battery life of wearables. In addition, an integrated analog front-end (AFE) eliminates the additional AFE typically needed to procure a separate chip and connect to the optical module.

The MAX30208 digital temperature sensor delivers clinical-grade temperature measurement accuracy (±0.1°C) with fast response time to changes in temperature. It also meets the power and size demands of small, battery-powered applications such as smartwatches and medical patches. It simplifies the design of battery-powered, temperature-sensing wearable healthcare applications. Easier to use than competitive offerings, it measures temperature at the top of the device and does not suffer from thermal self-heating like competitive solutions. MAX30208 is compatible with up to four I2C addresses to enable multiple sensors on the same IC bus. The MAX30208 can be attached to either a PCB or a flex printed circuit (FPC).

MAX30208 delivers ±0.1°C accuracy in the range of 30°C to 50°C and eliminates thermal self-heating, a factor that affects measurement accuracy in competitive devices. MAXM86161 cancels ambient light for greater accuracy and provides highest SNR (Nyquist SNR is 89 dB; 100 dB SNR with averaging). In addition, Maxim provides algorithms for motion compensation to increase measurement accuracy.

To extend battery life of wearables, the MAXM86161 consumes approximately 35 percent lower power versus the closest competitor, with less than 10 μA operating power (typical at 25sps) and 1.6μA in shutdown mode. Compared to the closest competitive solution, the MAX30208 consumes only half the power (67 μA operating current during active conversion vs. 135 μA) under a representative use case.

MAXM86161 is available in an OLGA package (2.9 mm × 4. 3mm × 1.4 mm), which is 40 percent smaller than the closest competitor. MAXM86161 includes three LEDs—red and infrared for SpO2 measurement and green for heart rate; MAX30208 is available in a 10-pin thin LGA package (2 mm × 2 mm × 0.75 mm).

The MAXM86161 is available at Maxim’s website for $4.41 (1000-up, FOB USA); also available from authorized distributors; The MAXM86161EVSYS# evaluation kit is available for $150

The MAX30208 is available at Maxim’s website for $1.25 (1000-up, FOB USA); also available from authorized distributors; The MAX30208EVSYS# evaluation kit is available for $56

Maxim Integrated | www.maximintegrated.com

 

 

Step-Down Converters Save Energy and Space in IoT Devices

STMicroelectronics has announced its ST1PS01 step-down converters. The devices are engineered for small size, low quiescent current and high efficiency at all values of load current, to save energy and real-estate in keep-alive point-of-load supplies and IoT devices such as asset trackers, wearables, smart sensors and smart meters.

Leveraging synchronous rectification, efficiency is 92% at 400 mA full load and 95% when delivering just 1 mA. Power-saving design features keep the quiescent current to a miserly 500 nA and include a low-power voltage reference. There is also a pulse-frequency counter for controlling converter current at light load, with two high-speed comparators to help minimize output ripple.
Integrated feedback-loop compensation, soft-start circuitry and power switches ensure a space-saving solution that requires just a few small-outline passives to complete the circuit. The typical inductor value is 2.2 µH. In addition, output-voltage selection logic not only saves external voltage-setting components but also gives flexibility to configure modules digitally at manufacture or let the host system change the output voltage on the fly. Eight variants, each with four optional output-voltage settings, allow a choice of regulated outputs from 3.3 V to 0.62 5V. All models feature a Power-good indicator.

A wide input-voltage range, from 1.8 V to 5.5 V, further enhances flexibility for designers by allowing various battery chemistries or configurations as simple as a single lithium cell and extending runtime as the battery discharges. ST1PS01 regulators are also ideal for devices powered from energy-harvesting systems and feature a low noise-architecture that allows use in noise-sensitive applications.

An evaluation board, STEVAL-1PS01EJR, helps developers quickly understand how to take advantage of the ST1PS01’s high energy efficiency and feature integration.

ST1PS01 regulators are now in full production, packaged as 400 µm-pitch flip-chip devices measuring just 1.11 mm x 1.41 mm, and priced from $0.686 for orders of 1, 000 pieces.

STMicroelectronics | www.st.com

 

U-blox Low Power GNSS Receiver Tapped for Smart Watch Design

Technologies from U‑blox and TransSiP have been selected for the recently announced PowerWatch 2 from MATRIX Industries. Power Watch 2 claims to be the world’s first GPS smartwatch that you never need to recharge. The smartwatch embeds the ultra‑small, ultra‑low power U‑blox ZOE‑M8B GNSS receiver. Meanwhile, TransSiP’s PI technology ensures energy harvested is used at maximum efficiency.

The PowerWatch 2 does away with cables and external batteries by continually topping up its battery using thermoelectric energy generated from body heat as well as solar energy. The watch can connect to your smartphone and display notifications on your wrist, while tracking activities and visualizing them using dedicated iOS and Android apps, as well as with popular third-party health and fitness platforms.

The PowerWatch 2 delivers location tracking using the low‑power U‑blox ZOE‑M8B GNSS receiver module that consumes as low as 12 mW. Packaged as a (System‑in‑Package), the 4.5 x 4.5 x 1.0 mm module helps achieve the watch’s comparatively low 16‑mm thickness. And concurrent reception of up to three GNSS constellations means that it delivers high accuracy positioning in challenging situations such as urban or dense forest environments and when swimming.

Satellite based positioning is typically the most power‑hungry process on a sports watch. Providing highly efficient conversion of harvested energy into a very quiet supply of DC power, TransSiP PI enhances the ability of the ZOE‑M8B GNSS receiver module incorporating U‑blox Super‑E technology, to strike an ideal balance between power and performance. Working on a tight power budget, the watch supports 30 minutes of continuous GNSS tracking per day, with unused time accumulating in the watch’s battery pack—powering two hours of location tracking every four days.

TransSiP | www.transsip.com

U‑blox | www.u‑blox.com

Tailored Solutions Tackle Design Needs for Wearables

Low Power Priorities

For wearable devices, every drop of power is precious. That’s driving designers of these embedded systems to attack the power challenge from multiple angles. Fortunately, a slew of analog, power and system ICs have emerged that address the wearable market’s particular needs.

By Jeff Child, Editor-in-Chief

While power is an important issue in any embedded system design, it’s especially critical in wearable devices. Today’s generation of wearable electronics require longer battery lives, more functionality and better performance—all in extremely small form factors. Wearables comprise a wide variety of products including smartwatches, physical activity monitors, heart rate monitors, smart headphones and more.
Today’s wearable electronic devices share some common design priorities. First, they have an extremely low budget for power consumption. And because they’re not suited to being powered by replaceable batteries, they usually require a way for the unit to be recharged. Meanwhile, most modern wearables require some kind of wireless connectivity.

Feeding those needs, chip vendors—primarily from the microcontroller (MCU) and analog sectors—over the past 12 months have announced a generous mix of solutions to help keep power consumption low, to aid recharging and to enable new capabilities while maintaining narrow power constraints. Chip and platform solutions aimed at wearables span the range from specialized power management ICs (PMICs), data converters and power regulator chips, to wireless charging solutions and even complete reference design platforms specially for wearables.

Wrist-Worn Health Gear

Wearables have evolved from being more than just fun devices for health and fitness. Using sophisticated sensors and other capabilities, devices are being designed to do virtual care monitoring, assess chronic conditions and evaluate overall well-being. Along just those lines, in September Maxim Integrated announced its Health Sensor Platform 2.0 (HSP 2.0) (Figure 1). This wrist-worn platform can be used for rapid prototyping, evaluation and development. It provides the ability to monitor electrocardiogram (ECG), heart rate and body temperature from a wrist-worn wearable, saving up to six months in development time, according to Maxim.

Figure 1
The Health Sensor Platform 2.0 is a wrist-worn platform that can be used for rapid prototyping, evaluation and development. It provides the ability to monitor electrocardiogram (ECG), heart rate and body temperature from a wrist-worn wearable.

In the past, system developers have found it challenging to derive precise ECG monitoring from the wrist—most alternatives require a wearable chest strap. Getting accurate body temperature typically requires using a thermometer at another location. Maxim has overcome these challenges in the HSP 2.0. by using its proprietary sensor and health monitoring technology.

Enclosed in a watch casing, the wrist-based form factor enables HSP 2.0 to provide basic functionality out of the box, with body-monitoring measurements starting immediately. Data can be stored on the platform for patient evaluation or streamed to a PC for analysis later. Unlike other wearables, the data measurements collected by the HSP 2.0 can be owned by the wearer. This alleviates data privacy concerns and enables users to conduct their own data analysis. Also, because HSP 2.0 is an open platform, designers can evaluate their own algorithms on the board. In addition, the modular format is future proof to quickly accommodate new sensors over time.

HSP 2.0 includes the following Maxim chips: the MAX32630 DARWIN low-power MCU for wearables; the MAX32664 ultra-low-power biometric sensor hub with embedded heart-rate algorithm; the MAX20303 PMIC; the MAX30205 human body temperature sensor with ±0.1°C accuracy; the MAX30001 single-channel integrated biopotential and bioimpedance analog front-end (AFE) solution; and the MAX86141 optical pulse oximeter and heart-rate sensor.

Energy Controller for Wearables

For its part, Renesas Electronics has been working on meeting extreme low power demands by applying innovations in semiconductor process development. In November the company unveiled an innovative energy-harvesting embedded controller that can eliminate the need to use or replace batteries in a device. Developed based on Renesas’ SOTB (silicon-on-thin-buried-oxide) process technology, the new embedded controller achieves extreme reduction in both active and standby current consumption. The extreme low current levels of the SOTB-based embedded controller enables system designers to completely eliminate the need for batteries in some of their products through harvesting ambient energy sources such as light, vibration and flow (Figure 2).

Figure 2
The extreme low current levels of the SOTB-based embedded controller enables system designers to completely eliminate the need for batteries in some of their products through harvesting ambient energy sources such as light, vibration and flow.

Although the solution was developed with IoT devices in mind, the controller is more broadly aimed at what they call the new market of maintenance-free, connected IoT sensing devices with endpoint intelligence. This includes health and fitness apparel, shoes, wearables, smart watches and drones. Renesas’ first commercial product using SOTB technology, the R7F0E embedded controller, is a 32-bit, Arm Cortex-based embedded controller. The device is capable of operating up to 64 MHz for rapid local processing of sensor data and execution of complex analysis and control functions.

The R7F0E consumes just 20 μA/MHz active current, and only 150 nA deep standby current, approximately one-tenth that of conventional low-power MCUs. According to the company, samples of the new R7F0E embedded controller are available now for beta customers, and samples are scheduled to be available for general customers from July 2019. Mass production is scheduled to start from October 2019.

LDO Regulator for Wearables

Achieving longer battery lives is a problem that can be attacked from many angles. Power regulator electronics are among those. With that in mind, Microchip Technology in October introduced a linear Low Dropout (LDO) regulator that extends battery life in portable devices up to four times longer than traditional ultra-low quiescent (IQ) LDOs. With an ultra-low IQ of 250 nA versus the approximately 1 µA operation of traditional devices, the MCP1811 LDO reduces quiescent current to save battery life, enabling end users to recharge or replace batteries less often (Figure 3).

Figure 3
With an ultra-low IQ of 250 nA versus the approximately 1 µA operation of traditional devices, the MCP1811 LDO regulator saves battery life, enabling end users to recharge or replace batteries less often.

Well suited for IoT and battery-operated applications such as wearables, remotes and hearing aids, the LDO reduces power consumption in applications by minimizing standby or shutdown current. Reducing standby power consumption is critical in remote, battery-powered sensor nodes, where battery replacement is difficult and operating life requirements are high. Available in package options as small as 1 mm x 1 mm, the MCP1811 consumes minimal board space to meet the needs of today’s compact portable electronic designs. Depending on the application and number of LDOs, designers can take advantage of the extra board space with a larger battery to further increase battery life.

An additional benefit the MCP1811 offers is faster load line and transient response when compared to other ultra-low IQ LDOs. Faster response times can accelerate wake-up speed in devices such as monitors or sensors that require immediate attention. Faster transient response can help designers avoid undervoltage and overvoltage lockout measures used in sensitive applications where transient spikes can lead to catastrophic results.

Secure Payments with Wearables

An important capability in a certain class of wearables is the ability to support electronic retail transactions directly from the wearable device. While this is arguably a whole separate technology category in itself, we’ll touch on a couple developments here. In November, Infineon Technologies announced an EMV-based payment solution for key chains, rings, wristbands, bracelets and other wearable devices.

The SECORA Pay W for Smart Payment Accessories (SPA) combines an EMV chip with the card operating system, payment applet as well as the antenna directly on the unit. As a turnkey solution it allows card vendors, device manufacturers, financial institutions or event organizers to quickly and cost-efficiently introduce fashion accessories for payment and even access.

Infineon’s SECORA Pay solutions portfolio comprises the SECORA Pay S for standard Visa and MasterCard payment cards, SECORA Pay X for applications with extended features such as multi-application, national debit and white label schemes or access management and SECORA Pay W for payment accessories. All SECORA turn-key solutions are pre-certified by Mastercard and Visa and will accelerate the deployment of contactless payment. The EMV Chip Specifications (www.emvco.com) define globally valid requirements for chip-based payment solutions and acceptance terminals. They enable secure contact- and contactless applications and the use of other emerging payment technologies.

Complete Payment SoC

Likewise a player in the contactless transaction market, STMicroelectronics (ST) back in October announced teaming up with Fidesmo to create a turnkey active solution for secure contactless payments on smart watches and other wearable technology. The complete payment system-on-chip (SoC) is based on ST’s STPay-Boost IC, which combines a hardware secure element to protect transactions and a contactless controller featuring proprietary active-boost technology that maintains reliable NFC connections even in devices made with metallic materials. Its single-chip footprint fits easily within wearable form factors (Figure 4).

Figure 4
The STPay-Boost IC combines a hardware secure element to protect transactions and a contactless controller featuring proprietary active-boost technology that maintains reliable NFC connections even in devices made with metallic materials. Its single-chip footprint fits easily within wearable form factors.

ST’s proprietary NFC-boosting active load modulation technology simplifies RF design and accelerates time to market by ensuring superior performance with little or no circuit optimization needed. A small-size antenna can sustain robust and reliable wireless connection, permitting smaller overall product dimensions and lower power consumption resulting in longer battery life.

Fidesmo’s MasterCard MDES tokenization platform completes the solution by allowing the user to load the personal data needed for payment transactions. Convenient Over-The-Air (OTA) technology makes personalization a simple step for the user without any special equipment. Kronaby, a Sweden-based hybrid smartwatch maker, has embedded the STPay-Boost chip in its portfolio of men’s and women’s smart watches that offer differentiated features such as freedom from charging and filtered notifications. The SoC with Fidesmo tokenization enables Kronaby watches to support a variety of services such as payments, access control, transportation and loyalty rewards.

Data Converters

Data converters also have role to play in efforts to meet the extreme low power needs of wearable devices. Along such lines, in December Texas Instruments (TI) introduced four tiny precision data converters (Figure 5). The new data converters enable designers to add more intelligence and functionality, while shrinking system board space. The DAC80508 and DAC70508 are eight-channel precision digital-to-analog converters (DACs) that provide true 16- and 14-bit resolution, respectively.

Figure 5
The DAC80508 and DAC70508 are eight-channel precision DACs that provide true 16- and 14-bit resolution, respectively. The ADS122C04 and ADS122U04 are 24-bit precision ADCs that feature a two-wire, I2C-compatible interface and a two-wire, UART-compatible interface, respectively.

The ADS122C04 and ADS122U04 are 24-bit precision analog-to-digital converters (ADCs) that feature a two-wire, I2C-compatible interface and a two-wire, UART-compatible interface, respectively. The devices are optimized for a variety of small-size, high-performance or cost-sensitive electronics applications such as wearables.

Both DACs include a 2.5-V, 5-ppm/°C internal reference, eliminating the need for an external precision reference. Available in a 2.4-mm-by-2.4-mm die-size ball-grid array (DSBGA) package or wafer chip-scale package (WCSP) and a 3-mm-by-3-mm quad flat no-lead (QFN)-16 package, these devices are up to 36% smaller than the competition, says TI. Meanwhile, the tiny, 24-bit precision ADCs are available in 3-mm-by-3-mm very thin QFN (WQFN)-16 and 5-mm-by-4.4-mm thin-shrink small-outline package (TSSOP)-16 options. The two-wire interface requires fewer digital isolation channels than a standard serial peripheral interface (SPI), reducing the overall cost of an isolated system. These precision ADCs eliminate the need for external circuitry by integrating a flexible input multiplexer, a low-noise programmable gain amplifier and other circuitry.

Memory Innovations

Among the latest innovations aimed at wearables from Cypress Semiconductor is an FRAM (ferroelectric random access memory)-based data logging solution. In November, Cypress introduced a nonvolatile data-logging solution with ultra-low power consumption. This solution is well suited for portable medical and wearable devices that demand nonvolatile memories to continuously log an increasing amount of user and sensor data while using as little power as possible.

Cypress’ Excelon LP FRAM is an energy-efficient device that provides instant-write capabilities with virtually unlimited endurance (Figure 6). This enables wearable systems to perform mission-critical data logging requirements while maximizing battery life. The Excelon LP series is available in a low-pin-count, small-footprint package that is suited for space-constrained, wearable applications.

Figure 6
The Excelon LP FRAM provides instant-write capabilities with virtually unlimited endurance. This enables wearable systems to perform mission-critical data logging requirements while maximizing battery life.

The Excelon LP series offers 4-Mb and 8-Mb industrial and commercial-grade densities with 50 MHz and 20 MHz Serial Peripheral Interface (SPI) performance. The series reduces power consumption with 100 nA hibernate and 1 µA standby modes that greatly improve a battery-powered product’s user experience by extending system operating time. The device’s inherent instant writes also eliminate power failure “data-at-risk” due to volatile data buffers in legacy memories. The family features wide voltage operation from 1.71 V to 3.6 V and is available in RoHS-compliant industry-standard packages that are pin compatible with EEPROMs and other nonvolatile memories. Excelon LP F-RAMs provide 1,000-trillion (1015) read/write cycle endurance with 10 years of data retention at 85°C or 151 years at 65°C.

Charging Wearables

A common aspect of wearable devices is that they tend not to be suited for replaceable batteries. As a result, they typically need to be recharged. Wireless (cordless) battery charging is beginning to take hold as a solution. Feeding such needs, in October Analog Devices announced its Power by Linear LTC4126 as an expansion of its offerings in wireless battery charging. The LTC4126 combines a wireless powered battery charger for Li-Ion cells with a high efficiency multi-mode charge pump DC-DC converter, providing a regulated 1.2 V output at up to 60 mA (Figure 7).

Figure 7
The LTC4126 combines a wireless powered battery charger for Li-Ion cells with a high efficiency multi-mode charge pump DC-DC converter, providing a regulated 1.2 V output at up to 60 mA.

Charging with the LTC4126 allows for a completely sealed end product without wires or connectors and eliminates the need to constantly replace non-rechargeable (primary) batteries. The efficient 1.2 V charge pump output features pushbutton on/off control and can directly power the end product’s ASIC. This greatly simplifies the system solution and reduces the number of necessary external components. The device is ideal for space-constrained low power Li-Ion cell powered wearables such as hearing aids, medical smart patches, wireless headsets and IoT devices.

The LTC4126, with its input power management circuitry, rectifies AC power from a wireless power receiver coil and generates a 2.7 V to 5.5 V input rail to power a full-featured constant-current/constant-voltage battery charger. Features of the battery charger include a pin selectable charge voltage of 4.2 V or 4.35 V, 7.5 mA charge current, automatic recharge, battery temperature monitoring via an NTC pin, and an onboard 6-hour safety charge termination timer. Low battery protection disconnects the battery from all loads when the battery voltage is below 3.0 V. The LTC4126’s charge pump switching frequency is set to 50 kHz/75 kHz to keep switching noise out of the audible range, ideal for audio related applications such as hearing aids and wireless headsets. The IC is housed in a compact, low profile (0.74 mm) 12-lead 2 mm × 2 mm LQFN package. The device is guaranteed for operation from –20°C to 85°C in E-grade.

Kit for Wireless Charging

Also facilitating building wireless chargers for wearables, ST for its part offers a kit-level solution. The ST plug-and-play wireless battery-charger development kit (STEVAL-ISB045V1) lets users quickly build ultra-compact chargers up to 2.5 W with a space-saving 20 mm-diameter coil, for charging small IoT devices and wearables such as smart watches, sports gear or healthcare equipment (Figure 8).

Figure 8
The ST plug-and-play wireless battery-charger development kit lets users quickly build ultra-compact chargers up to 2.5 W with a space-saving 20 mm-diameter coil, for charging small IoT devices and wearables such as smart watches, sports gear or healthcare equipment.

Built around the STWBC-WA wireless charging-transmitter controller, the kit comprises a charging base unit containing a transmitter board with the 20 mm coil already connected and ready to use. Getting started is easy, using the PC-based STSW-STWBCGUI software to configure the STWBC-WA and monitor runtime information such as power delivered, bridge frequency, demodulation quality and protocol status. The kit includes a dongle for running the GUI. The supporting ecosystem includes certified reference boards, software and detailed documentation to help developers quickly design chargers for wearables.

The STWBC-WA controller chip contains integrated drivers and natively supports full-bridge or half-bridge topologies for powering the antenna. The half-bridge option allows charging up to 1 W with a smaller-diameter coil for an even more compact form factor. The chip supports all standard wireless-charging features, including Foreign Object Detection (FOD) and active presence detection for safe charging, and uses digital feedback to adapt the transmitted power for optimum efficiency at all load conditions. Two firmware options give users the choice of a fast turnkey solution or customizing the application using APIs to access on-chip peripherals including an ADC, a UART and GPIOs.

Clearly there are many facets and angles to address the low power needs of wearables. As demands for more functionality rise, system developers will need to remain ever mindful of keeping battery life at the same lengths or longer. Fortunately, there seems to be no stopping the innovation among chip vendors targeting this growing wearables market.

RESOURCES

Analog Devices | www.analog.com
Cypress Semiconductor | www.cypress.com
Infineon Technologies | www.infineon.com
Maxim Integrated | www.maximintegrated.com
Microchip Technology | www.microchip.com
Renesas Electronics America | www.renesas.com
STMicroelectronics | www.st.com
Texas Instruments | www.ti.com

This article appeared in the March 344 issue of Circuit Cellar

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POWER MAKES IT POSSIBLE

Power Issues for Wearables
Wearable devices put extreme demands on the embedded electronics that make them work—and power is front and center among those demands. Devices spanning across the consumer, fitness and medical markets all need an advanced power source and power management technologies to perform as expected. Circuit Cellar Chief Editor Jeff Child examines how today’s microcontroller and power electronics are enabling today’s wearable products.

Power Supplies for Medical Systems
Over the past year, there’s been an increasing trend toward new products that have some sort of application or industry focus. That means supplies that include either certifications, special performance specs or tailored packaging intended for a specific application area such as medical. This Product Focus section updates readers on these technology trends and provides a product gallery of representative medical-focused power supplies.

DESIGN RESOURCES, ISSUES AND CHALLENGES

Flex PCB Design Services
While not exactly a brand-new technology, flexible printed circuit boards are a critical part of many of today’s challenging embedded system applications from wearable devices to mobile healthcare electronics. Circuit Cellar’s Editor-in-Chief, Jeff Child, explores the Flex PCB design capabilities available today and whose providing them.

Design Flow Ensures Automotive Safety
Fault analysis has been around for years, and many methods have been created to optimize evaluation of hundreds of concurrent faults in specialized simulators. However, there are many challenges in running a fault campaign. Mentor’s Doug Smith presents an improved formal verification flow that reduces the number of faults while simultaneously providing much higher quality of results.

Cooling Electronic Systems
Any good embedded system engineer knows that heat is the enemy of reliability. As new systems cram more functionality at higher speeds into ever smaller packages, it’s no wonder an increasing amount of engineering mindshare is focusing on cooling electronic systems. In this article, George Novacek reviews some of the essential math and science around cooling and looks are several cooling technologies—from cold pates to heat pipes.

MICROCONTROLLER PROJECTS WITH ALL THE DETAILS

MCU-Based Solution Links USB to Legacy PC I/O
In PCs, serial interfaces have now been just about completely replaced by USB. But many of those interfaces are still used in control and monitoring embedded systems. In this project article, Hossam Abdelbaki describes his ATSTAMP design. ATSTAMP is an MCS-51 (8051) compatible microcontroller chip that can be connected to the USB port of any PC via any USB-to-serial bridge currently available in the market.

Pet Collar Uses GPS and Wi-Fi
The PIC32 has proven effective for a myriad of applications, so why not a dog collar? Learn how Cornell graduates Vidya Ramesh and Vaidehi Garg built a GPS-enabled pet collar prototype. The article discusses the hardware peripherals used in the project, the setup, and the software. It also describes the motivation behind the project, and possibilities to expand the project in the future.

Guitar Video Game Uses PIC32
While music-playing video games are fun, their user interfaces tend leave a lot to be desired. Learn how Cornell students Jake Podell and Jonah Wexler designed and built a musical video game that’s interfaced with using a custom-built wireless guitar controller. The game is run on a Microchip PIC32 MCU and uses a TFT LCD display to show notes that move across the screen towards a strum region.

… AND MORE FROM OUR EXPERT COLUMNISTS

Non-Evasive Current Sensor
Gone are the days when you could do most of your own maintenance on your car’s engine. Today they’re sophisticated electronic systems. But there are some things you can do with the right tools. In his article, By Jeff Bachiochi talks about how using the timing light on his car engine introduced him to non-contact sensor technology. He talks about the types of probes available and how to use them to read the magnitude of alternating current (AC

Impedance Spectroscopy using the AD5933
Impedance spectroscopy is the measurement of a device’s impedance (or resistance) over a range of frequencies. Brian Millier has designed many voltammographs and conductivity meters over the years. But he recently came across the Analog Devices AD5933 chip made by which performs most all the functions needed to do impedance spectroscopy. In this article, explores the technology, circuit design and software that serve these efforts.

Side-Channel Power Analysis
Side-channel power analysis is a method of breaking security on embedded systems, and something Colin O’Flynn has covered extensively in his column. This time Colin shows how you can prove some of the fundamental assumptions that underpin side-channel power analysis. He uses the open-source ChipWhisperer project with Jupyter notebooks for easy interactive evaluation.

Low-Power PMIC Enables High Sensitivity Optical Measurements

Maxim Integrated Products has introduced its latest tiny, highly integrated power-management IC (PMIC). The ultra-low-power MAX20345 integrates a lithium charger and debuts a unique architecture that optimizes the sensitivity of optical measurements for wearable fitness and health applications. In wearables, optical-sensing accuracy is impacted by a variety of biological factors unique to the user. Designers have been striving to increase the sensitivity of optical systems, in particular the signal-to-noise ratio (SNR), to cover a broader spectrum of use cases.
Traditional low-quiescent-current regulators favored in wearable applications come with tradeoffs that degrade SNR on the wrist, such as high-amplitude ripple, low-frequency ripple and long-settling times. Some designers have even turned to high-quiescent-current alternatives to overcome these drawbacks, but they must deal with increased power consumption, which reduces battery runtime or requires a larger battery. According to Maxim, the MAX20345 features a first-of-its-kind buck-boost regulator based on an innovative architecture that’s optimized for highly accurate heart-rate, blood-oxygen (SpO2) and other optical measurements. The regulator delivers the desired low-quiescent current performance without the drawbacks that degrade SNR and, as a result, can increase performance by up to 7dB.

The MAX20345 is also the latest in a line of ultra-low-power PMICs for small wearables and IoT devices that help raise efficiency without sacrificing battery runtime. To meet these needs, the MAX20345 integrates a lithium-ion battery charger; six voltage regulators, each with ultra-low quiescent current; three nanoPower bucks (900 nA typical) and three ultra-low quiescent current LDO regulators (as low as 550 nA typical). Two load switches allow disconnecting of system peripherals to minimize battery drain. Both the buck-boost and the bucks support dynamic voltage scaling (DVS), providing additional power-saving opportunities when lower voltages can be deployed under favorable conditions. The MAX20345 is available in a 56-bump, 0.4mm pitch, 3.37 mm x 3.05 mm wafer-level package (WLP.)

Key Advantages

  • Superior Performance for Optical Systems: the integrated buck-boost regulator provides the low ripple at high frequency that will not interfere with optical measurements. These short settling times support the high-sensitivity optical-sensor measurements on wearables.
  • Extended Battery Life: regulators with nanoPower quiescent current reduce sleep and standby power, which in turn extends battery runtime and allows for smaller battery size. High-efficiency regulators preserve battery energy during active states.
  • Small Footprint: by eliminating multiple discrete components, the MAX20345 provides a sophisticated power architecture for space-constrained wearable and IoT designs.

The MAX20345 is available at Maxim’s website for $4.45 (1000-up, FOB USA) and is also available from authorized distributors. The MAX20345EVKIT# evaluation kit is available for $57.00

Maxim Integrated | www.maximintegrated.com

 

SIMO PMICs Shrink Power Regulator Size in Half

Six new low-power power-management integrated circuits (PMICs) from Maxim Integrated Products are designed to reduce the power-management footprint by up to 50 percent for space-constrained products such as wearables, hearables, sensors, smart-home automation hubs and internet of things (IoT) devices. They increase the overall system efficiency by nine percent compared to the closest competitive solution, while also reducing heat dissipation, an important consideration for wearable products that make skin contact.
The unique control architecture in the MAX17270 (shown), MAX77278, MAX77640/MAX77641 and MAX77680/MAX77681 PMICs allows a single inductor to serve as the critical energy-storage element for multiple, independent DC-rail outputs. This allows engineers to reduce the number of bulky inductors in their designs, thereby improving efficiency, shrinking form factor and reducing heat dissipation. In addition, the low quiescent current of the PMICs plays an important role in extending battery life. With the intrinsic buck-boost operation of the PMICs, the power rails can operate over a battery’s entire range.

MAX17270: Smallest Size and Lowest Quiescent Current
At 50 percent smaller than previous-generation SIMO-only solutions, the MAX17270 SIMO buck-boost converter provides the industry’s smallest solution size while reducing the number of inductors and ICs that are required for a power tree. Its quiescent current of 850nA for one SIMO channel and 1.3µA for three SIMO channels is the lowest in the market and helps extend battery life of end devices. In addition, the product’s low power consumption prevents overheating and reduces frequent charging cycles for wearables and hearables. They are available in TQFN and WLP package options.

MAX77278: Power Path Charger Optimized for Small Li+ Batteries
This ultra-low-power SIMO PMIC provides three buck-boost regulators with independent voltage outputs (0.8VOUT to 5.25VOUT), 16µA operating quiescent current/300nA standby current and flexible power sequencing. The device is also a charger for small Li+ cells (7.5mA – 300mA CC range). It includes an adjustable 425mA current sink for an LED, eight general-purpose input/output (GPIO) pins and a 3.7125V to 5.3V, 50mA low-noise low-dropout regulator (LDO) with fixed headroom control in a total solution size as low as 24mm2. The PMIC’s I2C interface allows an applications processor to monitor the status and control power management. The MAX77278 is ideal for remote controls, health and fitness monitors, body cameras and IoT applications.

MAX77640/MAX77641: Highly Integrated Battery Charging and Power Solutions
These ultra-low-power SIMO PMICs feature three buck-boost regulators, a low-noise 150mA LDO, a GPIO output port, a triple current sink for an RGB LED array and flexible power sequencing. Operating current is just 5.6µA and shutdown current is 300nA. Available in a 16mm2 total solution size, the MAX77640 and MAX77641 are ideal for applications with a built-in charger in areas like wearables, fitness and health monitoring and IoT.

MAX77680/MAX77681: Mini PMICs for Always-On, Low-Power Applications
These ultra-low-power SIMO PMICs provide three buck-boost regulators, 3.0µA operating quiescent current, 300nA shutdown current and flexible power sequencing. Total solution size is only 15.5mm2. Given their feature set, the MAX77680 and MAX77681 are ideal for more minimalistic platforms that require streamlined resources, such as hearables (Bluetooth headsets/earbuds) and miniaturized IoT devices (rings, watches, e-pens).

The MAX17270 is available for $1.84 (1000-up, FOB USA); the MAX77278 is available for $2.18 (1000-up, FOB USA); the MAX77680 and MAX77681 are available for $1.24 (1000-up, FOB USA); and the MAX77640 and MAX77641 are available for $1.71 (1000-up, FOB USA) at Maxim’s website. The ICs are also available from select authorized distributors.

The MAX17270EVKIT# evaluation kit is available for $100; the MAX77278EVKIT# evaluation kit is available for $100; the MAX77680/MAX77681EVKIT# evaluation kit is available for $100; and the MAX77640/MAX77641EVKIT# is available for $100.

Maxim Integrated | www.maximintegrated.com

Highly Integrated, Precision ADCs and DACs Feature Small Footprint

Texas Instruments (TI) has introduced four tiny precision data converters. The new data converters enable designers to add more intelligence and functionality, while shrinking system board space. The DAC80508 and DAC70508 are eight-channel precision digital-to-analog converters (DACs) that provide true 16- and 14-bit resolution, respectively. The ADS122C04 and ADS122U04 are 24-bit precision analog-to-digital converters (ADCs) that feature a two-wire, I2C-compatible interface and a two-wire, UART-compatible interface, respectively. The devices are optimized for a variety of small-size, high-performance or cost-sensitive industrial, communications and personal electronics applications. Examples include optical modules, field transmitters, battery-powered systems, building automation and wearables.

Both DACs include a 2.5-V, 5-ppm/°C internal reference, eliminating the need for an external precision reference. Available in a 2.4-mm-by-2.4-mm die-size ball-grid array (DSBGA) package or wafer chip-scale package (WCSP) and a 3-mm-by-3-mm quad flat no-lead (QFN)-16 package, these devices are up to 36 percent smaller than the competition. The new DACs eliminate the typical trade-off between high performance and small size, enabling engineers to achieve the best system accuracy, while reducing board size or increasing channel density.

In addition to their compact size, the DAC80508 and DAC70508 provide true, 1 least significant bit (LSB) integral nonlinearity to achieve the highest level of accuracy at 16- and 14-bit resolution – up to 66 percent better linearity than the competition. They are fully specified over a -40°C to +125°C extended temperature range and provide features such as cyclic redundancy check (CRC) to increase system reliability.

The tiny, 24-bit precision ADCs are available in 3-mm-by-3-mm very thin QFN (WQFN)-16 and 5-mm-by-4.4-mm thin-shrink small-outline package (TSSOP)-16 options. The two-wire interface requires fewer digital isolation channels than a standard serial peripheral interface (SPI), reducing the overall cost of an isolated system. These precision ADCs eliminate the need for external circuitry by integrating a flexible input multiplexer, a low-noise programmable gain amplifier, two programmable excitation current sources, an oscillator and a precision temperature sensor.

Both ADC devices feature a low-drift 2.048-V, 5-ppm/°C internal reference. Their internal 2 percent accurate oscillators help designers improve power-line cycle noise rejection, enabling higher accuracy in noisy environments. With gains from 1 to 128 and noise as low as 100 nV, designers can measure both small-signal sensors and wide input ranges with one ADC. These device families, which also include pin-to-pin-compatible 16-bit options, give designers the flexibility to meet various system requirements by scaling performance up or down.

Engineers can evaluate the new data converters with the DAC80508 evaluation module, the ADS122C04 evaluation module and the ADS122U04 evaluation module, all available today for $99.00 from the TI store and authorized distributors.

TI’s new tiny DACs and ADCs are available now with pricing ranging from $3.95 to $9.99 (1,000s).

Texas Instruments | www.ti.com

IoT Module Family Features Ultra-Compact Form Factor

Telit has announced the xE310 family of miniature IoT modules. With initial models planned in LTE-M, NB-IoT and European 2G, the new form factor will enable Telit to meet growing demand for ultra-small, high-performance modules for wearable medical devices, fitness trackers, industrial sensors, smart metering, and other mass-production, massive deployment applications. Telit will start shipping xE310 modules in Q4 this year.
Telit claims the xE310 family is one of the smallest LGA form factors available in the market with a flexible perimeter footprint supporting various sizes from compact to smaller than 200 mm2. The xE310’s 94 pads include spares to provide Telit the flexibility to quickly deliver support for additional features as technologies, applications and markets evolve. Spares can be used for modules supporting Bluetooth, Wi-Fi or enhanced location technologies—in addition to cellular—while maintaining compatibility with cellular only models. They can also be used for additional connections that may be required for new 5G-enabled features.

The new form factor also gives OEMs greater flexibility, efficiency and yield during design and manufacturing. The xE310 family provides easy PCB routing while minimizing manufacturing process issues such as planarity and bending. The unique circular pad facilitates correct package orientation for automated assembly.

To learn more about the new xE310 family, visit the Telit stand 431 at IoT Solutions World Congress in Barcelona, Spain on October 16-18.

For a look at how this new design is enabling smart metering applications, register for the Telit webinar on November 15: “From 2G to 5G: 5 things you need to know for smarter utilities”: https://www.smart-energy.com/industry-sectors/data_analytics/webinar-15-november-5-things-you-need-to-know-for-smarter-utilities/.

Telit | www.telit.com

Low-Power MCUs Extend Battery Life for Wearables

Maxim Integrated Products has introduced the ultra-low power MAX32660 and MAX32652 microcontrollers. These MCUs are based on the ARM Cortex-M4 with FPU processor and provide designers the means to develop advanced applications under restrictive power constraints. Maxim’s family of DARWIN MCUs combine its wearable-grade power technology with the biggest embedded memories in their class and advanced embedded security.

Memory, size, power consumption, and processing power are critical features for engineers designing more complex algorithms for smarter IoT applications. According to Maxim, existing solutions today offer two extremes—they either have decent power consumption but limited processing and memory capabilities, or they have higher power consumption with more powerful processors and more memory.
The MAX32660 (shown) offers designers access to enough memory to run some advanced algorithms and manage sensors (256 KB flash and 96 KB SRAM). They also offer excellent power performance (down to 50µW/MHz), small size (1.6 mm x 1.6 mm in WLP package) and a cost-effective price point. Engineers can now build more intelligent sensors and systems that are smaller and lower in cost, while also providing a longer battery life.

As IoT devices become more intelligent, they start requiring more memory and additional embedded processors which can each be very expensive and power hungry. The MAX32652 offers an alternative for designers who can benefit from the low power consumption of an embedded microcontroller with the capabilities of a higher powered applications processor.

With 3 MB flash and 1 MB SRAM integrated on-chip and running up to 120 MHz, the MAX32652 offers a highly-integrated solution for IoT devices that strive to do more processing and provide more intelligence. Integrated high-speed peripherals such as high-speed USB 2.0, secure digital (SD) card controller, a thin-film transistor (TFT) display, and a complete security engine position the MAX32652 as the low-power brain for advanced IoT devices. With the added capability to run from external memories over HyperBus or XcellaBus, the MAX32652 can be designed to do even more tomorrow, providing designers a future-proof memory architecture and anticipating the increasing demands of smart devices.

The MAX32660 and MAX32652 are both available at Maxim’s website and select authorized distributors. MAX32660EVKIT# and MAX32652EVKIT# evaluation kits are also both available at Maxim’s website.

Maxim Integrated | www.maximintegrated.com

The Dick Tracy Wristwatch TV

Input Voltage

–Jeff Child, Editor-in-Chief

JeffHeadShot

At my first technology editor job back in 1990, my boss at the time was obsessed with the concept of the Dick Tracy wristwatch. Dick Tracy was a popular comic strip that ran from the late 30s up until 1972. Now, let me be clear, even I’m not old enough to be from the era when Dick Tracy was part of popular culture. But my boss was. For those of you who don’t know, the 2-Way Wrist Radio was one of the comic strip’s most iconic items. It was worn by Tracy and members of the police force and in 1964 the 2-Way Wrist Radio was upgraded to a 2-Way Wrist TV. When chip companies came to visit our editorial offices—this is back when press tours were still a thing—in many editorial meetings with those companies, my boss would quite often ask the hypothetical question: “When are we going to get the Dick Tracy wristwatch?”

Confident that Moore’s Law would go on forever, semiconductor companies back then were always hungry to get their share of the mobile electronic device market—although the “device” of the day kept changing. My boss’s Dick Tracy wristwatch question was a clever way to spur discussion about chip integration, extreme low power, wireless communication and even full motion video. Full motion video on a mobile device in particular was a technology that many were skeptical could ever happen. In that early 90s period, the DRAM was the main driver of semiconductor process technology, and, in turn, the desktop PC was by far the dominant market for DRAMs. As a result, there was a tendency to view all future computing through the lens of the PC. It would be more than a decade later before flash memory surpassed DRAMs as the main driver of the chip business, and that was because the market size of mobile devices began to eclipse PCs.

As most of you know, Circuit Cellar has BYTE magazine as a part its origin story. Steve Ciarcia had a popular column called Circuit Cellar in BYTE magazine. When Steve founded this magazine three decades ago, he gave it the Circuit Cellar name. The April 1981 issue of BYTE magazine famously had a picture of basically a wristwatch with a CRT screen and keyboard with a mini-floppy disk being inserted into its side. That’s a vivid example that we humans are notoriously really bad at predicting what future technologies will look like. We have an inherent bias imposing what we have now on our view of the future.

Fast forward today and obviously we have the Dick Tracy Wristwatch and so much more—the Apple Watch being the most vivid example. Today’s wearable devices span across the consumer, fitness and medical markets and all need a mix of low-power, low-cost and high-speed processing. But even though technology has come a long way, the design challenges are still tricky. Wearable electronic devices of today all share some common aspects. They have an extremely low budget for power consumption, they tend not to be suited for replaceable batteries and therefore must be rechargeable. They also usually require some kind of wireless connectivity.

Today’s wearables including a variety of products including smartwatches, physical activity monitors, heart rate monitors, smart headphones and more. Microcontrollers for these devices have to have extremely low power and high integration. At the same time, power solutions servicing this market require mastery of low quiescent current design techniques and high integration. To meet those needs chip vendors—primarily from the microcontroller and analog markets—keep advancing solutions that consume extremely low levels and power and manage that power.

One amusing aspect of the Dick Tracy wristwatch was that it was referred as a 2-Way Radio (and later a 2-Way TV). With Internet connectivity, today’s smartwatches basically are connected to an infinite number of network nodes. I can’t claim to be a better predictor of the future than the editors of 1981’s BYTE. But now I need to come up with a new question to ask chip vendors, and I don’t know what the question should be. Perhaps: “When are we going to get the Star Wars holographic 3D image messaging system?”. And in wristwatch form please.

This appears in the May (334) issue of Circuit Cellar magazine

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