Monthly Archives: May 2023

Next-Generation Battery Management

Although there has been a significant advancement in increasing the range of electric vehicles, the charging speed is still a matter of concern. For instance, DC fast chargers can charge the battery to 80 percent in about 30 to 45 minutes. In contrast, it is possible to fill the gas tank in only a few minutes. Fast charging has its limitations, as the process generates a significant amount of heat. The high current and the internal resistance of the cable and the battery typically generate a significant rise in temperature.

EV batteries are typically rated at 400 V, and several factors limit their charging rate. This includes the cross-sectional area of the charging cable and the temperature of the battery cells. The temperature rise can be high enough for some fast-charging stations that necessitate liquid-cooling of their cables. Therefore, it would seem reasonable to expect that an increase in the battery’s voltage will boost the power it delivers.

Porsche, in their Taycan EV, has done just that. Their first production vehicle has a system voltage of 800 V rather than the usual 400. This would allow a 350 KW level 3 ultra-fast DC charging station to potentially charge the vehicle to 80% in as low as 15 minutes. But then, an EV design with an 800 V system requires new considerations for all its electrical systems, especially those related to managing the battery.

Switching the vehicle on and off requires the main contactors to electrically connect and disconnect the battery from the traction inverter. On the other side, there are independent contacts for connecting and disconnecting the battery to and from the charger buses and the DC link. For DC fast charging, additional DC charge contacts are necessary that can establish a connection from the battery to the DC charging station. Additionally, auxiliary contactors connect and disconnect the battery to electrical heaters for optimizing the passenger compartment temperature in cold weather conditions.

Moving to a higher battery voltage increases the potential for the formation of electrical arcs, and these can be damaging. Vehicle architectures operating at 800 V therefore, require stricter isolation parameters than those necessary for 400 V architecture. This can increase the cost of the vehicle.

For instance, higher voltage levels require the connector pins to have greater creepage and clearance between them to reduce the risk of arcing. Although connector manufacturers have managed to overcome these issues, the connectors are more expensive than those they offer for 400 V systems, thereby jacking up the total costs.

The maximum battery voltage decides the ratings of components that the traction inverter module uses. For battery voltages at 400 V, there is a wide range of selection of suitably rated components. But this range reduces drastically when the battery voltage is at 800 V. Most components for higher voltages come with a premium price tag attached. This raises the price of the traction inverter module.

A solution to the above problem is to use two 400 V batteries. To reduce the charging time, the batteries may connect in series. They can connect in parallel when driving.

SiC MOSFETs Enhance Performance and Efficiency

Power applications across industries demand smaller sizes, greater efficiency, and enhanced performance from the electronic equipment they use. These applications include energy storage systems, battery chargers, DC-DC and AC-DC inverters/converters, industrial motor drivers, and many more. In fact, the performance requirements have become so aggressive that they surpass the capabilities of silicon MOSFETs. Enter new transistor architectures based on silicon carbide or SiC.

Although silicon carbide devices do offer significantly enhanced benefits across most critical performance metrics, the first-generation SiC devices had various application uncertainties and limitations. The second-generation devices came with improved specifications. With pressures for time-to-market increasing, manufacturers improved the performance of SiC MOSFETs, and by the third generation of devices, there were vast improvements across key parameters.

While silicon-based MOSFETs significantly enhanced the design of power electronic equipment, the insulated-gate bipolar transistor or IGBT also helped. The IGBT is a functionally similar semiconductor, its construction is vastly different, and its switching attributes are more optimized. This led to power electronic equipment adopting switched topologies, thus becoming far more efficient and compact.

The main characteristics of switched mode topologies are based on some form of PWM or pulse-width modulation. They use a closed-loop feedback arrangement for maintaining the desired current, voltage, or power value. With the increasing use of silicon MOSFETs, the demand for better performance also increased. Regulatory mandates demanded new efficiency goals.

With a considerable effort in R&D, an alternative emerged. This was the SiC power-switching device, that used silicon carbide as the substrate rather than silicon. Deep-physics changes have allowed these SiC devices three major advantageous electrical characteristics over silicon-alone products. These characteristics offer operational advantages and subtle differences.

The first of these three main characteristics is a higher critical breakdown voltage. While silicon-based products offer 0.3 MV/cm, SiC-based products offer 2.8 MV/cm. This results in products with the same voltage rating now being available in a much thinner layer, effectively reducing the drain to source on-time resistance.

The second main characteristic is higher thermal conductivity. This allows SiC-based devices to handle much higher current densities in the same cross-sectional area, as compared to that silicon-based devices can.

The final characteristic is a wider bandgap. This is the difference in energy measured in electron volts between the bottom of the conduction band and the top of the valence band in many types of insulators and semiconductors. This results in a lower leakage current at higher temperatures. Because of the above reasons, the industry also refers to SiC devices as wide bandgap devices.

In general terms, SiC-based devices can handle voltages that are ten times higher than Si-only devices can. They can also switch about ten times faster, besides offering an on-time drain-to-source resistance of half or lower at 25 °C, even when using the same die area as a Si-only device. Moreover, the switching-related loss at turn-off periods for SiC devices is significantly lower than those for Si-based devices. Additionally, it is easier to handle thermal design and management issues with SiC-based devices, as they can operate at much higher temperatures, such as up to 200 °C, as compared to 125 °C for Si-based devices.

LDOs for Portables and Wearables

As electronic devices get increasingly smaller in form factor, they are also becoming more portable and relying more on battery power. These devices include security systems, fitness trackers, and Internet of Things or IoT devices. The design of such tiny devices demands high-efficiency power regulators that can make use of every milliwatt of power from each charge for extending the working life of the device. The efficiency of traditional linear regulators and switch-mode power regulators falls woefully short of the requirements. Moreover, transient voltages and noise in switch-mode power regulators are detrimental to their performance.

The most recent addition to switching and linear regulators is the LDO or the low-dropout voltage regulator. It lowers thermal dissipation while improving efficiency by operating with a very low voltage drop across the regulator. Low-to-medium power applications are well-served by various types of LDOs, as they are available in minuscule packages of 3 x 3 x 0.6 mm. In addition, there are LDOs with fixed or adjustable output voltages, including some versions with on-off control of the output.

A voltage regulator must maintain a constant output voltage even when the source or load voltages change. Traditional voltage regulator devices operate in one of two ways—linear or switched mode. While LDO regulators are linear regulators, they operate with a very low voltage difference between their output and input terminals. As with other linear voltage regulators, LDOs also function with feedback control.

This feedback control of the LDO functions via a resistive voltage divider that scales the output voltage. The scaled voltage enters an error amplifier that compares it to a reference voltage. The resulting output of the error amplifier drives the series pass element to maintain the output terminal with the desired voltage. The dropout voltage of the LDO is the difference between the input and output voltages, and this appears across the series pass element.

The series pass element of an LDO functions like a resistor whose value varies with the applied voltage from the error amplifier. LDO manufacturers use various devices for the series pass element. It can be a PMOS device, NMOS device, or a PNP bipolar transistor. While it is possible to drive into saturation the PMOS and PNP devices, the dropout voltage for PMOS-type FET devices depends on the drain-to-source on resistance. Although each of these devices has its own advantages and disadvantages, using PMOS devices for the series pass element has the lowest implementation cost. For instance, positive LDO regulators from Diodes Incorporated offer LDOs with PMOS pass devices featuring dropout voltages of about 300 mV, when their output voltage is 3.3 V and the load current is 1 A.

The output of the LDO must have an output capacitor. The inherent ESR or effective series resistance of the capacitor affects the stability of the circuit. That means the capacitor used must have an ESR of 10 ohms or lower for guaranteeing stability covering the entire operating temperature range. Typically, these capacitors are of the type multilayer ceramic, solid-state E-CAPs, or tantalum, with values upwards of 2.2 µF.

What are MOSFET Relays

For certain applications, especially for high-power switching, traditional electromagnetic relays are still a popular choice. However, with the advent of solid-state relays, particularly MOSFET Relays, this trend is now shifting for a growing range of applications. In addition, with IoT growing exponentially, and 5G networks moving the trend towards shrinking form factors, engineers are forced to fit more powerful devices with higher functionality into smaller spaces. That means, they must also find better ways of improving power efficiencies through improved switching speeds.

Modern IT infrastructure, such as switching power supplies and DC-DC converters, presents engineers with specific design challenges. MOSFET relays help to address these challenges as their characteristics are superbly suited to several key applications.

Although the name includes the word relays, MOSFET relays are actually electronic circuits rather than relays and feature an input and an output side. The input side comprises a PDA or photodiode dome array, along with an LED or Light Emitting Diode. The output side comprises a FET or Field Effect Transistor block, with a control circuit bridging the two.

To activate a MOSFET relay, a current must flow through its input LED and turn it on. The PDA then converts the light from the LED to a voltage. The control circuit uses this voltage to drive the output block. This action turns on the double MOSFETs, present in the output block, allowing them to pass either AC or DC loads bi-directionally.

Unlike electromagnetic relays, MOSFET relays have no moving parts. Therefore, the latter can withstand vibration and physical shock without suffering damage or malfunction. Ideally, the MOSFET relay should perform indefinitely, operate silently, and cause very little electrical interference, provided it is under proper use.

While MOSFET relays can handle a wide range of input voltages, they consume very little power and do not arc during operation. That makes this solid state relays eminently suitable for working in hazardous environments. While enabling the switching of both AC and DC signals, solid state relays minimize surge currents. A physical comparison with electromagnetic relays reveals MOSFET relays to be considerably smaller, occupying less space on printed circuit boards, and consuming very low power.

Certain characteristics of MOSFET relays offer advantageous implications in electronic applications. For instance, they offer low output capacitance, implying an improvement in switching times with better isolation characteristics for load signals at high frequencies. The presence of an LED at the input implies optical isolation between the input and output circuits offering a better physical or galvanic isolation. The on-resistance for MOSFETs is low, implying increased switching speeds and low power dissipation when switching high currents. Being solid state, MOSFET relays have no hysteresis when switching from the on-state to the off-state and vice versa. These relays have high linearity, ensuring there is no signal distortion when switching. Therefore, MOSFET relays are equally suitable for analog and low-level signal switching.

The above characteristics of the MOSFET relay make them ideally suitable for a wide range of applications. These include use in energy-related equipment, telecommunications, factory automation, amusement equipment, security equipment, medical equipment, automated test equipment, and much more.

Thermal Interface Materials for Electronics

As the name suggests, TIMs are Thermal Interface Materials that the electronic industry typically uses between two mating surfaces. They help to conduct heat from one metal surface to another. TIMs are a great help in thermal management, especially when removing heat from a semiconductor device to a heat sink. By acting as a filler material between the two mating surfaces, TIMs improve the efficiency of the thermal management system.

There are various types of material that can act as TIMs, and there are important factors that designers must consider when selecting a specific material to act as a TIM for a unique application.

Every conductor has its own resistance which impedes the flow of electrical current through it. Impressing a voltage across a conductor starts the free electrons moving inside it. Moving electrons collide against other atomic particles within the conductor, giving rise to friction and thereby generating thermal energy or heat.

In electronic circuits, active devices or processing units like CPUs, TPUs, GPUs, and light-emitting diodes or LEDs generate copious amounts of heat when operating. Other passive devices like resistors and transformers also release high amounts of thermal energy. Increasing amounts of heat in components can lead to thermal runaway, ultimately leading to their failure or destruction.

Therefore, it is desirable to keep electronic components cool when operating, thereby ensuring better performance and reliability. This calls for thermal management to maintain the temperature of the device within its specified limits.

It is possible to use both passive and active cooling techniques for electronic components. It is typical for passive cooling methods to use natural conduction, convection, or radiation techniques for cooling down electronic devices. Active cooling methods, on the other hand, typically require the use of external energy for cooling down components or electronic devices.

Although active cooling can be more effective in comparison to passive cooling, it is more expensive to deploy. Using TIMs is an intermediate method to enhance the efficiency of passive cooling techniques, but without excessive expense.

Although the mating surfaces of the component and its heat sink may appear flat, in reality, they are not. They typically have tool marks and other imperfections such as pits and scratches. The presence of these imperfections prevents the two surfaces from forming close physical contact, leading to air filling the space between the two non-mating surfaces. Air, being a poor conductor of heat, introduces higher thermal resistance between the interfacing surfaces.

TIMs, being a soft material, fills a majority of the gaps between the mating surfaces, expelling the air from between them. In addition, TIMs have better thermal conductivity than air does, typically, 100 times better, and their use considerably improves the thermal management system. As such, many industrial and consumer electronic systems use TIMs widely for ensuring efficient heat dissipation and preventing electronic components from getting too hot.

The electronic industry uses different forms of TIMs. These can be thermal tapes, greases, gels, thermal adhesives, dielectric pads, or PCMs that change their phase. The industry also uses more advanced materials such as pyrolytic graphite, as these are thermally anisotropic.

Generating Power from Space

At the beginning of this year, the SSPP or Space Solar Power Project of the California Institute of Technology launched a prototype SSPD or Space Solar Power Demonstrator into orbit. They have an aspiring plan of gathering solar power in space. Not only will the SSPD prototype test several vital components, but also beam the energy it collects back to earth.

Outer space has a practically unlimited supply of solar energy. This energy is constantly available, never subject to cloud cover, and is unaffected by seasons and cycles of day and night. Therefore, space solar power is a tremendous step towards harnessing limitless amounts of clean and free energy.

The launch is a major milestone for the project. In full realization, the SSPD will have several spacecraft in the form of a constellation for collecting sunlight. It will then transform the sunlight into electricity, and transmit it wirelessly over to earth. The project will provide electricity wherever necessary, including places that do not have access to reliable power.

A SpaceX rocket launched the 50-kg SSPD into space on a Transporter-6 mission. The demonstrator has three main experiments. Each handling a vital technology of the project.

The first experiment is the DOLCE. This is the on-orbit, deployable, ultralight composite. Measuring 6 x 6 feet, this structure is meant to demonstrate the packaging scheme, architecture, and deployment mechanism of the future modular spacecraft that the scientists eventually plan to make up as the kilometer-long constellation of the power station.

The next experiment is the ALBA. This is a collection of various types of photovoltaic cells. Numbering 32 in total, this experiment allows the scientists to make an assessment of the effective performance of each type of photovoltaic cell in the extremely hostile environment of space.

The final experiment is the MAPLE. This is a microwave array for transferring power at low orbit. It consists of an array of lightweight flexible power transmitters at microwave ranges. With precise timing control systems, it can focus the power onto two different receivers selectively. This experiment will demonstrate the transmission of wireless power at a distance in space.

The SSPD has an additional fourth experiment. This is a box of electronics interfacing the prototype with the Vigoride computer while providing a control for the three experiments.

The ALBA or photovoltaic cell experiment will require up to six months of testing before it can generate new insights into the most suitable photovoltaic technology for space power applications. MAPLE constitutes a series of experiments, starting from verification of the initial functionality to an evaluation of the system performance under extreme environments over time.

DOLCE has two cameras on booms that can deploy as necessary, and more cameras on the electronics system. They will monitor the progress of the experiments and provide a feedback stream to earth. According to the SSPD team, they expect to have a complete assessment of the experiments’ performance within a few months.

In the meantime, the team still has to deal with numerous challenges. This is because it is not possible to guarantee anything about conducting an experiment in space.

5G Modem for IoT and Wearable Devices

Although yet to become a commonplace scenario, we have been seeing and hearing about 5G quite often nowadays. For the most part, IoT devices and wearables are still in the realm of 4G LTE, while the rest of the industry has surged ahead. Now, Qualcomm is set to change that with the introduction of its Snapdragon X35 modem. With their new modem, Qualcomm aims to provide 5G support to these small devices. They are calling this technology 5G NR-Light, because of its reduced capability. According to the manufacturers, X35 modems will have a maximum downlink speed of around 220 Mbps and an uplink speed of around 100 Mbps.

Qualcomm claims their Snapdragon X35 will bring several breakthroughs in the world of 5G. Not only is the design of the world’s first 5G NR-Light modem cost-effective, but its streamlined form factor also leads to power efficiency. In addition, the company has designed the modem with optimized thermal performance. The company expects the Snapdragon X35 to power the next generation of intelligent connected edge devices while empowering an entire range of users. The company is eagerly waiting to work with industry leaders in unified 5G platforms and unleash the possibilities.

Although featuring a tiny form factor, NR-Light is mighty in performance. It features all the good aspects of 5G, starting from spectral efficiency and the ability to access new sub-6 GHz bands. High-end wearable devices, while incorporating the Snapdragon X35 modem, can communicate at the high speeds that 5G offers. In the industrial context, many IoT devices will be able to incorporate the X35 modem to improve their performance. The company is aiming its new modem at devices like Chromebooks, router products, low-end PCs, and many more. Another good feature is the new modem does not need an additional Qualcomm SoC to make it function.

To make it compatible with existing devices, Qualcomm has designed the Snapdragon X35 to support 4G LTE as well, as a fallback option. Even with such powerful features and working at such high speeds, the new modem consumes the lowest power of all the modems the company has manufactured so far. Although many other OEMs are showing a lot of interest, the first device to use this modem will emerge only in the first half of 2024. According to Qualcomm, the price of the Snapdragon X35 5G NR-Light modem will be around half that of its counterpart, the Snapdragon X55 modem.

Qualcomm has released more interesting features about their new modem. According to them, the Snapdragon X35 modem has the same interfaces as its predecessor LTE modems. This information is of vital importance for existing consumers with older designs. At least in theory, they can integrate the new modem in their designs with ease and avail the capabilities of 5G instantly.

Qualcomm has one more trick up its sleeve. They have announced another new modem, the Snapdragon X32, in addition to the Snapdragon X35 modem. They have designed the X32 modem as a modem-to-antenna solution suitable for use on lower-cost devices that work on NR-Light.

Future Diamond Transistors

At Northrop Grumman Mission Systems and Arizona State University, researchers are working on a new project, creating power transistors, but from diamond. They claim diamond power transistors are capable of very high efficiencies. This can significantly shrink the size of power transistors, leading to smaller electrical grid substations, and a potential drop in the cost of cell phone towers.

Manufacturers typically make power transistors from silicon. However, researchers are investigating diamond, because, they claim, it has very high thermal conductivity. Therefore, diamond conducts heat more than 8 to 10 times more efficiently than current materials like silicon. The researchers claim that at their full potential, transistors made of diamond can be smaller than regular power transistors by about 90 percent.

The breakdown field of diamonds is also high. That means, as compared to most other materials, a diamond can withstand large amounts of voltage, before failure. A high breakdown field is advantageous for applications involving high power. Therefore, diamond transistors will be vital to advancing the transition to renewable energy, while electrifying the transportation sector.

Although silicon has been the standard material for making most semiconductor devices, manufacturers also use gallium nitride and silicon carbide for the more advanced modern transistors, mainly for regulating the flow of electrical power. Now, researchers are studying the use of two new transistor materials—boron nitride and diamond,

The researchers are studying diamonds for the main body of the transistor, while they are interested in boron nitride as the electrical contact for the transistor. Similar to diamond, boron nitride, too, has high thermal conductivity and a high breakdown field,

The research team expects to make transistors by combining the two materials. According to them, the two materials complement each other, working even better than they do individually.

Their research will be useful for several applications, such as communication technologies. For instance, satellites typically operate on solar power, requiring transistors to turn power from solar panels into a form usable by the electronics. For launching satellites into space, one of the biggest impediments is its weight and size. Using a smaller power transistor can help to reduce both.

Smaller diamond transistors can improve many other communication technologies as well. This includes towers that cell phones need. Transistors handle the power that these tower systems need to produce radio frequencies for cell phone usage.

According to the researchers, cell phone designers and operators face a huge challenge of keeping the tower systems cool. This is especially true when the tower location is in hot environments, such as in Phoenix.

Cell phone towers typically use power transistors made of silicon, while the newer 5G towers use gallium nitride transistors. With their substantially better heat transfer characteristics, the new diamond transistors can drastically reduce the power needed to cool cell phone tower systems, and also make easier the task of keeping cell tower electronics from overheating.

In addition to communication technology, power conversion applications for electrical systems and the electrical grid will also benefit from the new power transistors made of boron nitride and diamond. Their higher efficiency will significantly reduce the size of electricity grid substations.

New MEMS Switches Accelerate Testing

If you are using processor ICs from Advanced Digital, testing them may be costly and logistically challenging. This is because testing these ICs requires isolated DC parametric test equipment, including high-speed digital ATE or automatic testing equipment to assuring the quality. New MEMS switch technology from ADI, working at 34 GHz, offers both DC and high-speed digital testing, despite having a small form factor in the form of a 5x4x0.9 mm LGA package. They reduce the test costs and simplify the logistics necessary for testing RF/digital SoCs or systems on chips.

There are many high-speed chips on the market. These include high-density inter-chip communications for advanced processors. Such advanced processors are the norm for 5G modems, computer graphics systems, and other central processing units. Therefore, ATE designers constantly face the increase in demand and complexity for throughput while assuring quality. For instance, the greatest challenge comes from the increasing number of transmitter/receiver channels, and these require both DC parametric and high-speed digital testing. Not only does this increase the testing time, but it also increases the complexity of the load board, while reducing the test throughput. In turn, this drives up operational expenses, while reducing the productivity of modern ATE environments.

One way of solving such ATE challenges requires a switch that not only operates at DC conditions but also at high frequencies. The new MEMS switch ADGM1001 from ADI, while passing true 0 Hz DC signals, can also operate equally effectively at high-speed signals up to 64 Gbps. Therefore, testing with these new switches requires only one insertion for an efficient single test platform. It is possible to configure the test platform for both DC parameter testing and standards for high-speed digital communications.

High-volume manufacturing requiring HSIO or high-speed input-output testing is often a challenge. Testing strategies typically employ a high-speed test architecture as a common approach for validating HSIO interfaces. Such test equipment typically incorporates two test paths in one configuration—one for DC tests, and the other for high-speed tests.

Testers employ a few methods for performing tests at both DC and high speed on HSIOs or digital SoCs. They may use relays, MEMS switches, or different load boards—one for DC testing, and the other for high-speed testing, but this requires two insertions.

Use of relays for DC and high-speed testing can be challenging. This is primarily due to relays being unable to operate beyond 8 GHz. Therefore, users must compromise on test coverage and signal speed. Moreover, relays take up large areas on PCBs on account of their larger size, and this makes the load boards rather large. Another concern with relays is their limited life and reliability. Relays typically only last for about 10 million cycles, thereby limiting the lifetime and system uptime of the load board.

With its superior density and small form factor, the 34 GHz MEMS switch from ADI offers both DC testing and high-speed digital testing capabilities, overcoming the above challenges.