Introduction
As automobiles continue to become more intelligent, safe, and comfortable, the amount of electrical systems and components continues to grow. With the addition of these components and systems comes a need for communication transceivers to facilitate their interaction in the most advantageous way possible for manufacturers. LIN was developed for this very reason: so car makers could manage communication between these components and systems in an efficient, straightforward fashion, where the bandwidth and versatility of CAN was not needed; though in most instances, it is a sub-bus to the CAN bus.

LIN® Specification Progression
The most up-to-date LIN standard was defined in 2010 (LIN 2.2A, the LIN Consortium). It was then transcribed to the International Organization for Standardization (ISO) to be accepted as ISO 17897 and officially released in 2016. Prior to 2010, LIN went through a series of revisions, being fully defined first in LIN 1.1 (1999), where the LIN Protocol Specification, LIN Configuration Language Specification, and LIN Application Interface Specification were established by a board called the LIN consortium. Each of these are necessary parts in creating the full LIN cluster in a way that is consistent across the market, allowing any car manufacturer to use the communication scheme. The LIN protocol specification describes the physical and data link layers, and the LIN Configuration Language enables the LIN cluster to be described in a file that is straightforward for any developer.

Workflow Concept
The LIN transceiver and its implementation are the focus of this paper; however, it is important to have a high-level understanding of the whole LIN network to understand the place of the transceiver in an application. As LIN became defined, it was not only specified for the actual 1’s and 0’s data delivery, but for a higher-level network implementation: The LIN workflow. The LIN workflow supports an easy-to-use, dependable implementation scheme for those working with the protocol. The configuration of the entire network cluster is defined and standardized, which is where the LIN Description File (LDF) comes in. The LDF is what differentiates the LIN clusters from each other, defining the specific use and properties for that cluster (node amount, amount and the description of message frames, message rate, and so forth). This allows the generation of software files by developers to establish what task each node in the cluster performs. The LDF can be used to automatically generate the software involved in communication, as well as supply information for measurement and test tools involved in the LIN cluster analysis.

The LDF is written using syntax defined by the LIN Configuration Language Specification. This syntax is used in combination with the System Defining Tool to create the LDF, and thus define the whole network. Along with these tools, there is the LIN Node Capability Language, which allows the developer to define and describe the implementation of Off-the-Shelf Nodes, which are easily-implementable, general-purpose LIN nodes designed for typical applications that can be bought in large quantities.

Continue Reading

As electronic devices get smaller, lighter, and thinner, the associated optics must do the same. Fortunately, some of the technologies of electronics are also applicable to optics, and vice versa, as demonstrated by a recent collaborative effort between Argonne National Laboratory and Harvard University. The team integrated two technologies—microelectromechanical systems (MEMS) and metalenses—to design and produce a lens that sits on top of a steerable platform and can be made with the same technology used to fabricate ICs.

The project is described in an article in APL Photonics, “Dynamic metasurface lens based on MEMS technology.” Additional fabrication and characterization details are in a Supplementary Information document. The complete device measures just 900 microns in diameter and 10 microns in thickness; a two-dimensional (2D) scanning MEMS platform controls the angle of the lens along two orthogonal axes by up to about ±9° each, which enables dynamic beamsteering. Potential applications include miniaturized microscope systems, LiDAR scanners, and projection systems.

1. The metasurface lens functions as a focusing reflective surface when illuminated by a collimated beam. (Source: Argonne National Laboratory/Harvard University)

By using the metasurface itself to separate the incident and reflected beam paths, there’s no need for a beam splitter, thus eliminating one of the bulky optical components often used in optical systems. Figure 1 shows a schematic of the reflective metasurface lens when a collimated, incident Gaussian beam at angle θ is focused at a distance f along the normal axis to the lens surface.

The metasurface lens mirrors, also called resonators or cells, are fabricated using standard photolithography techniques on a silicon-on-insulator (SOI) wafer with a 2-μm-thick top-device layer, a 200-nm buried-oxide layer, and a 600-μm-thick handle layer (Fig. 2).

2. Each unit cell of the metasurface lens consists of a 50-nm-thick gold disc on 400-nm-thick silicon-dioxide substrate with a 200-nm-thick gold backplane. (Source: Argonne National Laboratory/Harvard University)

The mirror dimensions are 1 × 1 mm and a thickness of 10 μm; resonance is about 1 kHz for each torsional axis. The actual details of the metalens/MEMS fabrication and attaching the cells to the MEMS surface are impressive; the paper and supplement provide the details. The MEMS cells have varying diameters from 1.2 to 2.0 μm, so they can be tightly packed onto the planar surface (Fig. 3). They reflect mid-IR light (λ = 4.6 μm), which the metalens focuses without need for additional optical components, such as a focusing lens.

3. This scanning electron microscope (SEM) image of the fabricated lens shows the varying sizes of the mirror cells, used to create the desired lens-plane density. (Source: Argonne National Laboratory/Harvard University)

The 2D scanner with integrated flat lens is actuated by electrostatic vertical “comb” drives, which are interdigitated stationary and rotating plates. Applying a voltage between these plates causes the moving elements to be pulled downward, causing rotation around an axis (Fig. 4).

4. This SEM shows a bare MEMS platform with a square layout with each side measuring 900 µm; the gimbal axes are called out. (Source: Argonne National Laboratory/Harvard University)

The micromirror is electrostatically rotated about its inner axis using the vertical comb drives mounted on the gimbal frame, while the gimbal frame itself rotates about the outer axis using the vertical comb drives mounted on its frame and substrate. This is analogous to the gimbaling used on a two-degree-of-freedom mechanical gyroscope. The finished device is mounted in a DIP package.

5. This optical-microscope image of a MEMS scanner with a flat lens on top also indicates the two rotational axes of the scanner; the inset shows the device mounted on a dual-in-line (DIP) package ready for wiring and electrostatic actuation. (Source: Argonne National Laboratory/Harvard University)

The prototype lens assembly, consisting of 374 cells of varying diameters (Fig. 5), was designed to be “perfectly” flat. But, of course, that’s not the case; its curvature was measured using an optical profilometer. The reflected beam path is at 0.5° compared to the designed value of 0°, and the full width at half maximum (FWHM)—analogous to the 3-dB bandwidth in electronics—becomes wider, at 41.7 µm compared to 22.8 μm.

6. This experimental arrangement was used for characterization of the optical response of the “flat lens.” (Source: Argonne National Laboratory/Harvard University)

The optical focusing performance was also evaluated using incident light (laser at 4.6 μm) with a beam only slightly larger than the 800-μm square lens and angled at 45° to the unactuated scanner. The profile of the reflected focal line was measured for three positions of the MEMS platform (Fig. 6). 

7. In the three experimental test configurations, the MEMS scanner is actuated to move the lens by rotational angles of 0°, 1°, and 2.5°, respectively, while the angle of the incident illumination remains unchanged. To align with the peak of the reflected signal, the position of the detector needs to be at 0°, 2.7°, and 7.3°, respectively. (Source: Argonne National Laboratory/Harvard University)

Voltages of 0 V (unactuated), 40 V, and 60 V were applied across the outer axis so that the lens tilts by 0°, 1°, and 2.5°, respectively (Fig. 7). The corresponding measured FWHM of the focal lines for the three tilted positions of the lens are shown in Figure 8.

8. Shown is the measured FWHM of the focal lines for the three tilted positions of the lens in Fig. 7. (Source: Argonne National Laboratory/Harvard University)

While networks based on using the ubiquitous powerline don’t have the glamor or speed of Ethernet or Wi-Fi (to cite just two examples), they’re a hardware- and cost-effective solution for energy management and building a smarter grid. To address their unique interface needs, as well as the multiple protocols in use among utilities and in different countries, Microchip developed the PL360B powerline modem IC. It implements a range of existing and emerging industry-standard Power Line Communication (PLC) protocols, including ITU G.9903 (G3-PLC) and ITU G.9904 (PRIME), as well as CENELEC-, FCC-, and ARIB-compliant applications.

This programmable PLC modem supports narrowband operation in any frequency band up to 500 kHz (Fig. 1). The critical front-end interface includes a programmable gain amplifier (PGA) with automatic gain control (AGC) for analog-to-digital converter operation over a wide dynamic range. The digital-to-analog converters and transmission driver support direct-line driving or external Class-D amplifier driving, along with digital transmission-level control. Furthermore, the device supports two independent transmission branches for the PLC signal.

1. The PL360B IC from Microchip Technologies eases the challenge of implementing a powerline modem, meeting a wide array of multiple industry and regulatory standards.

In addition to the interface, the IC implements a high-performance architecture combining a CPU, specific coprocessors for digital signal processing, and dedicated hardware accelerators for common narrowband PLC tasks. It includes an ARM 32-bit Cortex-M7 core-managing PL360 system comprised of co-processors, hardware accelerators and peripherals, as well as dedicated SRAM memories for code and data.

Then there’s data security, an increasingly important issue, despite (or perhaps as a consequence of) the nature of the powerline media. The PLC360B addresses this with a cryptographic engine and secure boot, and supports AES-128, 192, 256 standards. In addition, the secure-boot feature supports AES-128 CMAC for authentication, and AES-128 CBC for decryption. Security is also enhanced by the availability of fuse-programming control for decryption and authentication with 128-bit keys.

Effective use of ICs such as the PL360B involves numerous hardware and software issues. Not only does the 57-page datasheet provide detailed insight into the IC operation, registers, sequencing, and interconnection, it also shows the functions of the critical coupling block that resides between the IC and the AC mains (Fig. 2). On top of that, Microchip provides modem reference designs (design files, bill of materials, and schematics) for applications such as a complete electricity meter with PLC, a single PLC modem, and a master PLC device in charge of mastering the complete network of PLC nodes.

2. Key to an effective modem is the coupling block, which is the link between the well-behaved and constrained IC environment and the harsh powerline reality.

For those who prefer or need to explore and evaluate, the company also offers an evaluation kit with two evaluation boards and free G3-PLC and PRIME-PLC communications firmware used to establish point-to-point communication. The kit includes PC tools for assessing the performance of the PL360B, including a PHY tester for point-to-point test, a PLC “sniffer” to capture PLC traffic in a deployed network, and a PLC manager to manage the resulting network.

The PL360B requires a single 3.3-V supply voltage for its digital and analog I/O, and incorporates a +1.25-V voltage regulator for its core functions. It comes housed in TQFP-48 and QFN-48 packages, specified for operation over the −40 to +85°C temperature range. The PLC360B IC is priced at $2 each in 10,000-piece lots, while the ATPL360 evaluation kit goes for $500.

RIGOL’s Multi-Domain Debug App Note shows engineers how to combine the power of Real-Time Spectrum Analyzers with high-performance Oscilloscopes to make investigating, correlating, and analyzing signals easier. Today, a single product routinely combines RF, digital, and analog design elements. Learn how to use test instruments to see design issues in embedded signals, RF signals, or radiated emissions while locating the root cause whether it is an RF, power, embedded, emissions, layout, component, or mechanical issue.

When I get a printed-circuit-board (PCB) layout back for review, there are a few things I look for first. I can usually get a feeling for what kind of board designer has been at work, too, specifically if s/he is (or s/he thinks s/he is) a “digital” designer, an “RF” designer, or a “power” designer.

You might have formed the impression by now that I can be something of a picky customer. I know what I like in my PCB designs. In my younger years, I designed a fair few—over 300, from what I can piece together from the archeological residues of a lifetime in electronic engineering. And while some of these designs had modest digital content, the vast majority of them were for systems intended for low- to medium-frequency analog signal conditioning and processing done to (I hoped) a world-class performance level.

When the first PC-based board design tools appeared, I threw myself into board design with gusto. At last, control over how I wanted things done! No more would I have to lean over the shoulder of the guy with the arcane layout skills, the tape, and the scalpel, and yell “No, route it there! Route it there!” (We are still friends, by the way, after meeting the first time some 40 years ago when he was testing a home-build amplifier while on his lunch hour. I see him every Christmas for drinks.)

Naturally, I didn’t know nearly as much about how to do good layout as I thought I did, and I made plenty of mistakes. “The man who never made a mistake never made anything!” my dad used to preach, and it’s a wise observation. I’ve made plenty of mistakes in the past, in multiple contexts, including in the search for how to get the best performance out of a circuit when it makes that transition from your head to FR4.

Running Aground

So, let’s get back on track (spontaneous and unintended pun alert). What did I look for first in this latest design? Well, since this is another episode of “The Chronicles of GND,” it won’t surprise you to learn that my first checks are GND-related. Specifically, related to this system being, as is nearly every design I encounter these days, a “single-supply” system. What does that mean?

Well, analog circuitry from the Golden Age of Operational Amplifiers, during which I learned much of my craft, was almost always powered from a “split supply,” typically +15 V and −15 V by the time I started in the industry. Instead of having two terminals on your power-supply box (plus and minus), you had three (plus, “nought volts,” and minus).

The reasons for this are lost in the fog of time, but one thing is clear. Much of the development work on the kinds of analog circuits I’m referring to—amplifiers, integrators, and filters—came from early Analog Computers. In such systems, voltages (and sometimes currents) were the “analog” of a variable or result that the computer was required to “compute.” And since that result could be either a positive or a negative number, it was sensible that the circuits could operate with positive or negative voltages, with respect to a reference that represented a result of zero.

The circuits in a typical “split-supply” system draw current from the plus terminal of the supply, and return it to the minus terminal. Sometimes a little current may end up routing to “nought volts,” usually due to resistive voltage dividers and resistors from various circuit nodes to “nought volts.”

However, “nought volts” was never thought of as a supply rail like plus or minus. It’s a reference point, where your scope ground clip or the (mandatory, of course) second lead of your two-leaded voltmeter would connect. It was also likely to be connected to a nice ground plane under the insulating surface of your bench, and to the safety grounds of all the test equipment that kept the lab warm in winter.

Now, of course, “nought volts” was the spiritual precursor to GND. In fact, we often called it “ground,” and things connected to it as “grounded.” Since it was connected to the electrical safety “earth,” it was even possible that it found its way back to some metal buried deep in the actual ground, snuggling up to Mother Earth itself. So fundamental are the mythic origins of GND.

All for Nought?

Fast forward to today’s “single-supply” systems. Here your circuits have a positive supply, but they don’t have a negative supply. Or (pause for theatrical effect…) do they? Well, yes, they do. It just happens to be at (ostensibly) the same potential as GND. Effectively, the value of the negative power-supply voltage is zero. So that means you can just connect it to GND and be done with it, right? No one in their right mind would go to the bother of building a power supply whose output voltage is zero.

Well, maverick that I am, I’m here to tell you that—in principle, at least—that’s exactly what you should do to get the best and most predictable results from your board layouts.

This is because that negative power supply has a job to do. It has to sink the current “coming out” of the negative supply pin of each of your amplifiers, comparators, and whatnot. And this current is likely to be signal- and load-dependent. You do not want this flowing through all of the same conductors that direct your lovely clean GND reference to the sensitive points of your amplifier circuits and converters.

For anything that’s a “power” pin required to be at GND potential, you should connect it to a separate net, often called 0 V (“nought volts!”), to represent this negative power supply of value zero. 0 V will have to be connected to GND at some point; this is best done at the “star point,” where the power actually arrives at the board or subsystem. This connection should not be done as any kind of copper on the board that your software can recognize as conductive. I sometimes define a small copper object that I can place as needed.

The netlist should contain two completely distinct nets, GND and 0 V, so you can eyeball the netlist to be completely sure that pins are connected to the correct nets. You do do a visual inspection of your design netlists, don’t you? Become familiar with one of the simple, easily readable netlist formats and export your netlist into that format to check it.

Some people call 0 V “dirty ground.” But it really has nothing to do with GND at all, except that it’s very close in potential to it.

By this point you might be asking “What’s wrong with letting all of these currents mix and just having a super-low-impedance ground plane to keep all of the voltage drops small?” Well, small isn’t zero, for one thing. In some systems, microvolts can matter. And there are some very specific reasons in op-amp-based circuits why you should be suspicious about the currents coming out of the negative supply pins. For instance… no, only kidding, I’m going to leave you hanging on that thought until next time.

Meanwhile, as usual, agreements and disagreements are welcome through the usual channels. Has something about a single-supply system “ground” you down? Let me know!

We think of Interior walls for defining and dividing areas (and providing a place to hang things), but what if they could easily and cheaply be transformed into sensors? That’s what a joint project team from Carnegie Mellon Institute School of Computer Science and the Disney Research Pittsburgh has done, as detailed in a paper presented at the ACM CHI Conference on Human Factors in Computing Systems.

Their highly readable paper, “Wall++: Room-Scale Interactive and Context-Aware Sensing” provides full details on how they used conductive paint to add a dual-function role to a standard wall, providing a mutual-capacitance sensor for close-range sensing plus an electromagnetic-field sensor for wider-area performance. The result is what they call the Wall++, which can become part of a “smart” infrastructure to sense human touch, detect gestures, and even determine when appliances are in use.

Rather than opt for a surface of complex sensors, the team strived to meet three broad and difficult objectives:

• Low cost—they avoided expensive, conductive paint laced with silver, and instead used low-cost paint containing nickel.
• Easy to apply—no special skills are needed, using a standard paint roller and taped-off areas.
• invisible to the occupant—the conductive pattern is covered with a coat of regular latex paint to enhance surface durability and hide the electrodes.

In capacitive-sense mode, the wall operates somewhat like a touchpad, with its electric field reacting to any contact with a hand or body. In electromagnetic-field mode, the electrodes detect the distinctive electromagnetic (EM) signatures of electrical/electronic devices, allowing the system to identify and locate nearby devices. It can also track the location of a nearby person wearing a device that emits an EM signal.

1. The conductivity test involved different paints across three backing materials. Shown is a close-up of painted surface. Silver paint was deleted due to its high cost, while carbon paint was eliminated due to its high resistance. (Source: Carnegie Mellon)

The paper details more than just their final approach. It also shows alternatives they investigated and discarded among choice of conductive paints, backing materials, application methods, number of coats, and topcoats. They also evaluated different electrode patterns for sensing range and resolution, using an LCR meter to measure electrical impedance at 100 kHz. Tests included carbon, water-based nickel, acrylic-based nickel, and silver paints (Fig. 1); application using brush, roller, and spray (Fig. 2); and standard wallpaper, drywall, and primed drywall as backings.

2. Conductivity tests with different application methods and number of coats showed that roller painting yielded the highest conductivity and lower variance across the surface, and proved to be the fastest application method. (Source: Carnegie Mellon)

Tests went beyond just the materials and their application, though. They also tested sensor patterns based on lines, stripes, half circles, diamonds, and circle dots. The diamond pattern proved best, and subsequently they checked different pattern sizes and pitch (Fig. 3) using model-based simulations and actual tests.

3. The electrode patterns were also studied, with transmitters in red and receivers in blue (top); electric-field simulations of electrodes in the black region (higher voltages in red) were also performed (bottom). (Source: Carnegie Mellon)

The final configuratin has 70-cm electrodes at a 48-cm pitch, painted on a 12 × 8 ft. (3.7 × 2.4 m) wall (Fig. 4) with 22 columns and 15 rows of electrodes. This required 37 coaxial-cable connections to custom-built sensing electronics, with two multiplexed front ends (one for capacitive sensing and the other for EM-field sensing).

4. Painter’s tape was laid down in a crosshatched pattern (A & B), and then painted with a roller (C) to create a grid of regular diamonds (D). (Source: Carnegie Mellon)

Testing and evaluation began with sensing of “no-signal” conditions to establish a baseline and correct for inevitable inconsistencies of the paint layering. The data reduction divided the wall into a grid pattern; then they looked at the sensed outputs of each grid box relative to its neighbors.

For capacitance-mode testing, they evaluated sensing of walls being touched, as well as a hand hovering at a 10-cm standoff. They tested the ability to sense the body pose of users close to the wall (Fig. 5).

5. In the user study, six poses were used (top left) and their capacitive images were averaged (bottom left). The “confusion matrix” for six poses is key to decoding the data and deriving a conclusion. (Source: Carnegie Mellon)

For EM-field sensing of nearby appliances and their on/off state, the team rearranged the single-wall configuration into evenly distributed column antennas around the room periphery to support two-dimensional localization, and added algorithms to minimize the effects of inevitable EMI. They then used received signal strength (RSS) as the basis for analysis and triangulation of signals from each known appliance.

Tests also involved the wall’s ability to localize people wearing wristbands which transmitted a steady 1.5-MHz signal. As expected, distance errors decreased as the number of EM-tracking antennas increased (Fig. 6).

6. The tracking-distance error for appliances (left) and users (right) is a function of the different numbers of column antennas. Here, it’s shown with three locations tested. (Source: Carnegie Mellon)

Due to its low cost and ease of “installation,” the team foresees various possibilities for their Wall++ approach, such as placing wall light switches or other controls wherever is most convenient, or for gesture-based control of videogames. The monitoring could also be used to adjust light levels when a TV is turned on, or alert a user in another location when a laundry machine or electric kettle turns off.

Why didn’t they do this sooner? That’s the question some embedded engineers designing with microcontrollers (MCUs) are asking about the idea of adding analog signal-chain components in MCUs. With today’s sophisticated semiconductor manufacturing methods and special designs, how hard could it be to put a batch of linear circuits right on the same chip with the processor and memory?

Embedded designers of sensing and measuring devices almost always have to use external analog circuits to condition sensor signals before they can be processed. Just a few of the typical signal-conditioning operations include amplification, filtering, noise mitigation, switching, and data conversion. Such circuitry often takes up more space in the final product than the microcontroller chip itself. Today, though, you can get some MCUs with analog circuits on-chip to fit almost any sensing application.

Analog Enhancements

Some MCUs have had on-chip circuits that facilitate analog functions for years. These include an analog-to-digital converter (ADC), comparators, and pulse-width-modulation (PWM) capability. Now more integrated analog components are being incorporated in some MCU products.

One such example is the smart analog combo (SAC) modules from Texas Instruments. Each module consists of a flexible, programmable-gain op amp and a 12-bit digital-to-analog converter (DAC). Internal switches and multiplexers permit the op amp to be configured in multiple ways that may include inverting and non-inverting amplifiers, a follower, or transimpedance amplifier (TIA).

Figure 1 shows the SAC module. The op amp is a single-supply design that requires a bias voltage to center the output within the output voltage range available (2 to 3.6 V). An internal resistive feedback network allows you to select multiple fixed gain settings from 1 to 33. A power-mode selection feature permits a higher gain bandwidth and slew rate if low power consumption is not too much of a problem.

Download this article in PDF format.

Why didn’t they do this sooner? That’s the question some embedded engineers designing with microcontrollers (MCUs) are asking about the idea of adding analog signal-chain components in MCUs. With today’s sophisticated semiconductor manufacturing methods and special designs, how hard could it be to put a batch of linear circuits right on the same chip with the processor and memory?

Embedded designers of sensing and measuring devices almost always have to use external analog circuits to condition sensor signals before they can be processed. Just a few of the typical signal-conditioning operations include amplification, filtering, noise mitigation, switching, and data conversion. Such circuitry often takes up more space in the final product than the microcontroller chip itself. Today, though, you can get some MCUs with analog circuits on-chip to fit almost any sensing application.

 Sponsored Resources: 

• Smart Analog Combo Enabling Sensing and Measurement Applications
• How to use the smart analog combo modules in MSP430 MCUs
• Get more signal chain from your MCU in factory automation applications

Analog Enhancements

Some MCUs have had on-chip circuits that facilitate analog functions for years. These include an analog-to-digital converter (ADC), comparators, and pulse-width-modulation (PWM) capability. Now more integrated analog components are being incorporated in some MCU products.

One such example is the smart analog combo (SAC) modules from Texas Instruments. Each module consists of a flexible, programmable-gain op amp and a 12-bit digital-to-analog converter (DAC). Internal switches and multiplexers permit the op amp to be configured in multiple ways that may include inverting and non-inverting amplifiers, a follower, or transimpedance amplifier (TIA).

Figure 1 shows the SAC module. The op amp is a single-supply design that requires a bias voltage to center the output within the output voltage range available (2 to 3.6 V). An internal resistive feedback network allows you to select multiple fixed gain settings from 1 to 33. A power-mode selection feature permits a higher gain bandwidth and slew rate if low power consumption is not too much of a problem.

1. Shown is the general configuration of the smart analog combo modules that are now available in Texas Instruments’ MSP430 series of MCUs.

The module’s DAC is a 12-bit device that can be used for bias, reference-level selection, or as a way to generate an output waveform from a lookup table. Note the programmable switches and multiplexers select the inputs to the op amp that, in turn, set the desired configuration. Programming the MCU now includes the ability to program the configuration of this circuit.

Some MCU versions have up to four SACs. If the analog subsection of the design requires more complex circuitry, the SAC modules could be combined or cascaded. The only external components are any resistors, capacitors, or diodes that may be needed for the design.

These SACs are now available in Texas Instruments’ MSP430 series of MCUs. This family of embedded controllers features a 16-bit RISC architecture, ferroelectric RAM (FRAM), multiple I/O interfaces, and very low power consumption. The MSP430FR235x can be had with 0, 1, 2 or 4 SACs.

Smart Analog Combo Sensing and Measurement Applications

Almost any sensor application can benefit from onboard analog features. Typical applications target building automation, factory automation with industrial monitoring and control, and medical health and fitness. Some examples include smoke and gas detectors, temperature sensing, 4- to 20-mA control-loop sensors, and a blood glucose meter or oximeter.

2. This gas sensor is implemented with two SAC modules that are cascaded.

Figure 2 shows an example application—a circuit that conditions a gas sensor. An LED illuminates a reverse-biased photodiode. The amount of current in the diode is a function of the amount of gas present between the LED and sensor diode. The diode is connected to an op amp in the general-purpose (GP) mode; it’s configured as a TIA where the output is equal to the photodiode current in feedback resistor R_f. One of the DACs sets the bias voltage. Another gain stage may be needed to provide gain. The circuit in the figure is an inverting amplifier with the bias set by a second DAC. The resulting output is sent to the MCU’s onboard ADC. Software takes over from that point.

Microcontrollers are quickly adapting to the needs of different sensing and measurement applications. This is done through flexible on-chip analog signal-chain configurations that can be adjusted to meet application needs. Get an overview of the configurable smart analog combo modules (DACs, OpAmps/PGAs) in the MSP430FR2355 MCU with the references listed below. The whitepaper includes example smart analog combo configurations of several applications including smoke detectors, temperature transmitters, gas detectors and more.

 Sponsored Resources: 

• Smart Analog Combo Enabling Sensing and Measurement Applications
• How to use the smart analog combo modules in MSP430 MCUs
• Get more signal chain from your MCU in factory automation applications

Texas Instruments, the world’s largest supplier of analog chips, ousted its chief executive for conduct running afoul of the company’s standards. The company announced on Tuesday that it would replace Brian Crutcher, who only came into the role in June, with the chief executive he replaced, Texas Instruments chairman Rich Templeton.

Texas Instruments said that Crutcher resigned over violations of the company’s code of conduct. But the Dallas, Texas-based company did not say what specifically he had done. The company said that Crutcher’s resignation came after it uncovered “personal behavior that is not consistent with our ethics and core values, but not related to company strategy, operations or financial reporting.”

“For decades, our company’s core values and code of conduct have been foundational to how we operate and behave, and we have no tolerance for violations of our code of conduct,” Mark Blinn, lead director of the company’s board, said in a statement. The company said that Templeton is not a placeholder; the board is not conducting a search for his replacement.

When Crutcher was named chief executive in January, he was clearly meant to preserve the stability of Texas Instruments. Sales of the company’s analog chips have been growing steadily as cars and industrial equipment are equipped with sensors and computer chips to make them smarter and more efficient. Its products are used in tens of thousands of electronics devices.

Crutcher had been with Texas Instruments since 1996. He had been in charge of business operations and global manufacturing since he was promoted to chief operating officer last year. He previously presided over the company’s analog and digital light processing businesses.

Templeton was chief executive of Texas Instruments for 13 years before stepping down in June. The company cut through the sourness of Crutcher’s departure by disclosing its second-quarter revenue ahead of its earnings report next Tuesday. The company said that it earned $4.02 billion in second quarter revenue, nine percent higher than the same quarter last year. Profit was $1.40 per share.

Crutcher is the latest C.E.O. to be ousted from the semiconductor industry over improper conduct. Last month, Brian Krzanich stepped down as Intel’s chief executive after the company uncovered that he once had a consensual relationship with another employee, a violation of its non-fraternization policy. He held that position since 2013. That was followed by the firing of Ron Black, chief executive of Rambus.

Providing the interface circuitry for the sensors of physical parameters is a major role undertaken by many analog-circuit designers. However, even experienced engineers doing sensors for basics such as temperature, pressure, or position may be unfamiliar with the highly specialized probe arrangements that are standard in electrochemical sensing. These require potentiostat and electrochemical impedance spectroscopy (EIS) functionality to properly assess characteristics of solutions widely used in “wet chemistry” analysis.

To simplify the interface design and provide high-accuracy results, Analog Devices has introduced the ADuCM355 precision analog front end plus microcontroller for applications such as industrial gas sensing, instrumentation, vital-signs monitoring, and even disease management (Fig. 1).

1. The ADuCM355 for potentiostat-based chemical-solution assessment provides not only the sophisticated, precision analog front end, but also an advanced microcontroller for function management, security, and I/O—all at extremely low power.

The company claims that this highly integrated, single-chip device also has the most advanced sensor diagnostics, best-in-class low-noise and low-power performance, and smallest form factor of available approaches, which presently require multiple devices for comparable performance. Furthermore, it’s the only solution available that supports the basic dual-sensor potentiostat designs as well three- and four-sensor electrode implementations. The IC goes beyond being an analog interface, though—it includes a microcontroller based on the Arm Cortex-M3 processor specially designed to control and measure chemical and biosensors.

Sensor Specifics and the PGSTAT

In potentiostatic mode, a potentiostat/galvanostat (PGSTAT) controls the potential of the counter electrode (CE) (sometimes referred to as the auxiliary electrode, AE) versus the working electrode (WE), to ensure that the potential difference (voltage) between the WE and a reference electrode (RE) equals a user-specified value (Fig. 2).

2. This simplified, high-level block diagram of a potentiostat shows the relationship among the three electrodes and the circuitry needed for their analog input and output. (Source: Yihan Zhang, Columbia University)

In galvanostatic mode, the current flow between the WE and the CE is controlled. In a complete design, the voltage between the RE and WE and the current flow between the CE and WE are continuously monitored and controlled by a closed-loop, negative-feedback mechanism.

Just two electrodes are used in a basic measurement configuration, with the “chemistry of interest” at the WE; the CE functions as the other half of the cell, completing the circuit and maintaining a constant interface potential regardless of current value. However, it’s difficult to simultaneously maintain a constant CE potential as current is flowing, and compensate for voltage drop across the chemical solution itself.

To overcome those problems, the three-electrode approach of WE, CE, and RE is used (in some special configurations, a fourth electrode is added). The entire arrangement is somewhat analogous to using 3- or 4-wire Kelvin sensing to measure voltage across a load resistor or at contact points while eliminating the effects of contact resistance and IR drop in leads.

Among its features, the ADuCM355 offers:

• Voltage, current, and impedance measurement
• Dual ultra-low-power, low-noise potentiostats: 8.5 µA, 1.6 µV RMS
• Flexible 16-bit, 400-ksample/s measurement channel with advanced sensor diagnostics
• Integrated analog hardware accelerators
• 26-MHz core, 128-kB flash, 64-kB SRAM
• Security/safety via hardware crypto accelerator with AES-128/AES-256; hardware CRC with programmable polynomial generator; and read/write protection of user flash
• Two precision voltage references
• UART, I²C, and SPI serial input/output; up to 10 GPIO pins; external interrupt option; and general-purpose, wakeup, and watchdog timers

The IC is housed in a 6- × 5-mm, 72-lead LGA package and operates from a single 2.8- to 3.6-V supply. In hibernate mode, but with bias to external sensors, it requires just 8.5 µA while current drain in full shutdown mode is 2 µA. It’s fully specified for −40 to +85°C ambient operation and priced at $5.90 each in 1000-piece lots. The EVAL-ADUCM355QSPZ kit (Fig. 3) uses a PC plus USB connection so that users can evaluate the performance of the ADuCM355 across a range of different electrochemical techniques.

3. The PC-based, USB-linked EVAL-ADUCM355QSPZ kit lets users evaluate the ADuCM355 in various electrochemical techniques, including chronoamperometry, voltammetry, and electrochemical impedance spectroscopy.

References

Metrohm Autolab B.V, Autolab Application Note EC08, “Basic overview of the working principle of a potentiostat/galvanostat (PGSTAT) – Electrochemical cell setup”.

The Analytical Sciences Digital Library, “Analytical Electrochemistry: The Basic Concepts”.

University of Notre Dame, The Prashant Kamat Laboratory, “Potentiostat”.

Introduction

Radiated emissions testing for electromagnetic interference (EMI) can reveal issues that send engineers back to the drawing board to revise their product. Design revisions and additional test time increase product costs and delay schedules while engineers debug and solve EMI issues.

Smart Gate Drive technology in TI motor drivers helps customers solve their radiated EMI issues without costly board revisions or extra test time. With selectable IDRIVE currents for driving external FETs, EMI emissions from the motor-driver section of a system can be minimized by a simple serial interface (SPI) command or resistor change.

Continue Reading

Introduction

In an ideal world, gate drivers would connect directly to MOSFET gates and the motor drive system would operate perfectly. However, the real world creates a variety of issues for motor drive designers that cause them to add extra external components between a gate driver's outputs and the external power-stage FETs. The example in Figure 1 shows that each external power MOSFET may need up to four additional components for a designer to mitigate possible FET gate drive issues. For a three-phase driver, a designer might use up to twenty-four external components between the gate driver IC and triple halfbridge FETs.

The main reasons designers add these components are to improve radiated electromagnetic interferance (EMI) performance, protect the gate driver and FETs, and eliminate unintentional FET turn-on from switching transients. Adding these components to the gate driver increases board area and bill of materials (BOM) cost in motor drive designs. TI's Smart Gate Drive features eliminate the need for these external components while helping designers meet their EMI, robustness, and performance goals.

Continue Reading

We think of Interior walls for defining and dividing areas (and providing a place to hang things), but what if they could easily and cheaply be transformed into sensors? That’s what a joint project team from Carnegie Mellon Institute School of Computer Science and the Disney Research Pittsburgh has done, as detailed in a paper presented at the ACM CHI Conference on Human Factors in Computing Systems.

Their highly readable paper, “Wall++: Room-Scale Interactive and Context-Aware Sensing” provides full details on how they used conductive paint to add a dual-function role to a standard wall, providing a mutual-capacitance sensor for close-range sensing plus an electromagnetic-field sensor for wider-area performance. The result is what they call the Wall++, which can become part of a “smart” infrastructure to sense human touch, detect gestures, and even determine when appliances are in use.

Rather than opt for a surface of complex sensors, the team strived to meet three broad and difficult objectives:

• Low cost—they avoided expensive, conductive paint laced with silver, and instead used low-cost paint containing nickel.
• Easy to apply—no special skills are needed, using a standard paint roller and taped-off areas.
• invisible to the occupant—the conductive pattern is covered with a coat of regular latex paint to enhance surface durability and hide the electrodes.

In capacitive-sense mode, the wall operates somewhat like a touchpad, with its electric field reacting to any contact with a hand or body. In electromagnetic-field mode, the electrodes detect the distinctive electromagnetic (EM) signatures of electrical/electronic devices, allowing the system to identify and locate nearby devices. It can also track the location of a nearby person wearing a device that emits an EM signal.

1. The conductivity test involved different paints across three backing materials. Shown is a close-up of painted surface. Silver paint was deleted due to its high cost, while carbon paint was eliminated due to its high resistance. (Source: Carnegie Mellon)

The paper details more than just their final approach. It also shows alternatives they investigated and discarded among choice of conductive paints, backing materials, application methods, number of coats, and topcoats. They also evaluated different electrode patterns for sensing range and resolution, using an LCR meter to measure electrical impedance at 100 kHz. Tests included carbon, water-based nickel, acrylic-based nickel, and silver paints (Fig. 1); application using brush, roller, and spray (Fig. 2); and standard wallpaper, drywall, and primed drywall as backings.

2. Conductivity tests with different application methods and number of coats showed that roller painting yielded the highest conductivity and lower variance across the surface, and proved to be the fastest application method. (Source: Carnegie Mellon)

Tests went beyond just the materials and their application, though. They also tested sensor patterns based on lines, stripes, half circles, diamonds, and circle dots. The diamond pattern proved best, and subsequently they checked different pattern sizes and pitch (Fig. 3) using model-based simulations and actual tests.

3. The electrode patterns were also studied, with transmitters in red and receivers in blue (top); electric-field simulations of electrodes in the black region (higher voltages in red) were also performed (bottom). (Source: Carnegie Mellon)

The final configuratin has 70-cm electrodes at a 48-cm pitch, painted on a 12 × 8 ft. (3.7 × 2.4 m) wall (Fig. 4) with 22 columns and 15 rows of electrodes. This required 37 coaxial-cable connections to custom-built sensing electronics, with two multiplexed front ends (one for capacitive sensing and the other for EM-field sensing).

4. Painter’s tape was laid down in a crosshatched pattern (A & B), and then painted with a roller (C) to create a grid of regular diamonds (D). (Source: Carnegie Mellon)

Testing and evaluation began with sensing of “no-signal” conditions to establish a baseline and correct for inevitable inconsistencies of the paint layering. The data reduction divided the wall into a grid pattern; then they looked at the sensed outputs of each grid box relative to its neighbors.

For capacitance-mode testing, they evaluated sensing of walls being touched, as well as a hand hovering at a 10-cm standoff. They tested the ability to sense the body pose of users close to the wall (Fig. 5).

5. In the user study, six poses were used (top left) and their capacitive images were averaged (bottom left). The “confusion matrix” for six poses is key to decoding the data and deriving a conclusion. (Source: Carnegie Mellon)

For EM-field sensing of nearby appliances and their on/off state, the team rearranged the single-wall configuration into evenly distributed column antennas around the room periphery to support two-dimensional localization, and added algorithms to minimize the effects of inevitable EMI. They then used received signal strength (RSS) as the basis for analysis and triangulation of signals from each known appliance.

Tests also involved the wall’s ability to localize people wearing wristbands which transmitted a steady 1.5-MHz signal. As expected, distance errors decreased as the number of EM-tracking antennas increased (Fig. 6).

6. The tracking-distance error for appliances (left) and users (right) is a function of the different numbers of column antennas. Here, it’s shown with three locations tested. (Source: Carnegie Mellon)

Due to its low cost and ease of “installation,” the team foresees various possibilities for their Wall++ approach, such as placing wall light switches or other controls wherever is most convenient, or for gesture-based control of videogames. The monitoring could also be used to adjust light levels when a TV is turned on, or alert a user in another location when a laundry machine or electric kettle turns off.

Why didn’t they do this sooner? That’s the question some embedded engineers designing with microcontrollers (MCUs) are asking about the idea of adding analog signal-chain components in MCUs. With today’s sophisticated semiconductor manufacturing methods and special designs, how hard could it be to put a batch of linear circuits right on the same chip with the processor and memory?

Embedded designers of sensing and measuring devices almost always have to use external analog circuits to condition sensor signals before they can be processed. Just a few of the typical signal-conditioning operations include amplification, filtering, noise mitigation, switching, and data conversion. Such circuitry often takes up more space in the final product than the microcontroller chip itself. Today, though, you can get some MCUs with analog circuits on-chip to fit almost any sensing application.

Analog Enhancements

Some MCUs have had on-chip circuits that facilitate analog functions for years. These include an analog-to-digital converter (ADC), comparators, and pulse-width-modulation (PWM) capability. Now more integrated analog components are being incorporated in some MCU products.

One such example is the smart analog combo (SAC) modules from Texas Instruments. Each module consists of a flexible, programmable-gain op amp and a 12-bit digital-to-analog converter (DAC). Internal switches and multiplexers permit the op amp to be configured in multiple ways that may include inverting and non-inverting amplifiers, a follower, or transimpedance amplifier (TIA).

Figure 1 shows the SAC module. The op amp is a single-supply design that requires a bias voltage to center the output within the output voltage range available (2 to 3.6 V). An internal resistive feedback network allows you to select multiple fixed gain settings from 1 to 33. A power-mode selection feature permits a higher gain bandwidth and slew rate if low power consumption is not too much of a problem.

Download this article in PDF format.

Why didn’t they do this sooner? That’s the question some embedded engineers designing with microcontrollers (MCUs) are asking about the idea of adding analog signal-chain components in MCUs. With today’s sophisticated semiconductor manufacturing methods and special designs, how hard could it be to put a batch of linear circuits right on the same chip with the processor and memory?

Embedded designers of sensing and measuring devices almost always have to use external analog circuits to condition sensor signals before they can be processed. Just a few of the typical signal-conditioning operations include amplification, filtering, noise mitigation, switching, and data conversion. Such circuitry often takes up more space in the final product than the microcontroller chip itself. Today, though, you can get some MCUs with analog circuits on-chip to fit almost any sensing application.

 Sponsored Resources: 

• Smart Analog Combo Enabling Sensing and Measurement Applications
• How to use the smart analog combo modules in MSP430 MCUs
• Get more signal chain from your MCU in factory automation applications

Analog Enhancements

Some MCUs have had on-chip circuits that facilitate analog functions for years. These include an analog-to-digital converter (ADC), comparators, and pulse-width-modulation (PWM) capability. Now more integrated analog components are being incorporated in some MCU products.

One such example is the smart analog combo (SAC) modules from Texas Instruments. Each module consists of a flexible, programmable-gain op amp and a 12-bit digital-to-analog converter (DAC). Internal switches and multiplexers permit the op amp to be configured in multiple ways that may include inverting and non-inverting amplifiers, a follower, or transimpedance amplifier (TIA).

Figure 1 shows the SAC module. The op amp is a single-supply design that requires a bias voltage to center the output within the output voltage range available (2 to 3.6 V). An internal resistive feedback network allows you to select multiple fixed gain settings from 1 to 33. A power-mode selection feature permits a higher gain bandwidth and slew rate if low power consumption is not too much of a problem.

1. Shown is the general configuration of the smart analog combo modules that are now available in Texas Instruments’ MSP430 series of MCUs.

The module’s DAC is a 12-bit device that can be used for bias, reference-level selection, or as a way to generate an output waveform from a lookup table. Note the programmable switches and multiplexers select the inputs to the op amp that, in turn, set the desired configuration. Programming the MCU now includes the ability to program the configuration of this circuit.

Some MCU versions have up to four SACs. If the analog subsection of the design requires more complex circuitry, the SAC modules could be combined or cascaded. The only external components are any resistors, capacitors, or diodes that may be needed for the design.

These SACs are now available in Texas Instruments’ MSP430 series of MCUs. This family of embedded controllers features a 16-bit RISC architecture, ferroelectric RAM (FRAM), multiple I/O interfaces, and very low power consumption. The MSP430FR235x can be had with 0, 1, 2 or 4 SACs.

Smart Analog Combo Sensing and Measurement Applications

Almost any sensor application can benefit from onboard analog features. Typical applications target building automation, factory automation with industrial monitoring and control, and medical health and fitness. Some examples include smoke and gas detectors, temperature sensing, 4- to 20-mA control-loop sensors, and a blood glucose meter or oximeter.

2. This gas sensor is implemented with two SAC modules that are cascaded.

Figure 2 shows an example application—a circuit that conditions a gas sensor. An LED illuminates a reverse-biased photodiode. The amount of current in the diode is a function of the amount of gas present between the LED and sensor diode. The diode is connected to an op amp in the general-purpose (GP) mode; it’s configured as a TIA where the output is equal to the photodiode current in feedback resistor R_f. One of the DACs sets the bias voltage. Another gain stage may be needed to provide gain. The circuit in the figure is an inverting amplifier with the bias set by a second DAC. The resulting output is sent to the MCU’s onboard ADC. Software takes over from that point.

Microcontrollers are quickly adapting to the needs of different sensing and measurement applications. This is done through flexible on-chip analog signal-chain configurations that can be adjusted to meet application needs. Get an overview of the configurable smart analog combo modules (DACs, OpAmps/PGAs) in the MSP430FR2355 MCU with the references listed below. The whitepaper includes example smart analog combo configurations of several applications including smoke detectors, temperature transmitters, gas detectors and more.

 Sponsored Resources: 

• Smart Analog Combo Enabling Sensing and Measurement Applications
• How to use the smart analog combo modules in MSP430 MCUs
• Get more signal chain from your MCU in factory automation applications

Texas Instruments, the world’s largest supplier of analog chips, ousted its chief executive for conduct running afoul of the company’s standards. The company announced on Tuesday that it would replace Brian Crutcher, who only came into the role in June, with the chief executive he replaced, Texas Instruments chairman Rich Templeton.

Texas Instruments said that Crutcher resigned over violations of the company’s code of conduct. But the Dallas, Texas-based company did not say what specifically he had done. The company said that Crutcher’s resignation came after it uncovered “personal behavior that is not consistent with our ethics and core values, but not related to company strategy, operations or financial reporting.”

“For decades, our company’s core values and code of conduct have been foundational to how we operate and behave, and we have no tolerance for violations of our code of conduct,” Mark Blinn, lead director of the company’s board, said in a statement. The company said that Templeton is not a placeholder; the board is not conducting a search for his replacement.

When Crutcher was named chief executive in January, he was clearly meant to preserve the stability of Texas Instruments. Sales of the company’s analog chips have been growing steadily as cars and industrial equipment are equipped with sensors and computer chips to make them smarter and more efficient. Its products are used in tens of thousands of electronics devices.

Crutcher had been with Texas Instruments since 1996. He had been in charge of business operations and global manufacturing since he was promoted to chief operating officer last year. He previously presided over the company’s analog and digital light processing businesses.

Templeton was chief executive of Texas Instruments for 13 years before stepping down in June. The company cut through the sourness of Crutcher’s departure by disclosing its second-quarter revenue ahead of its earnings report next Tuesday. The company said that it earned $4.02 billion in second quarter revenue, nine percent higher than the same quarter last year. Profit was $1.40 per share.

Crutcher is the latest C.E.O. to be ousted from the semiconductor industry over misconduct. Last month, Brian Krzanich stepped down as Intel’s chief executive after the company uncovered that he once had a consensual relationship with another employee, a violation of its non-fraternization policy. He held that position since 2013. That was followed by the firing of Ron Black, chief executive of Rambus.