The Kynix Blog

Summary Energy-efficient sensor nodes are crucial to the development of the industrial internet of things (IIoT).Engineering team are trying to optimise energy efficient IIoT sensor nodes.In many cases, these devices will have to perform for years on a single battery charge. That calls for an implementation that is as energy efficient as possible. Achieving this demands a holistic approach to energy optimisation, one that reaches from the system level down to process and circuit-design choices.     Problem met Engineering team are trying to optimise the energy comsumption of an IIOT sensor node is that many of the design decisions interact with each other. And there are often hidden complexities of designs that lead to energy consumption being much higher than expected. For example, conventional wisdom points to the power consumption of an RF transmitter being a major influence on total energy. But, even though the receiver element may consume far less instantaneous power, system-level decisions that call for the device to listen for intermittent updates from a server can lead to it being left active for long periods of time – tens of seconds per hour versus tens of milliseconds for the transmitter. Because of the long operational life of a typical IoT sensor node, the energy used even when subsystems are sleeping can be responsible for a heavy drain on the battery.   Integration Despite the complex interaction between application design and implementation, there are some high-level choices that are likely to lead toward an optimal solution. One of these is the use of integration. Although it is entirely possible to use 2D-IC and 3D-IC multi chip packaging to assemble a compact IIoT sensor node from off-the-shelf components, integration into a single custom integrated circuit (IC) provides not just significant benefits in terms of cost and size but reductions in power consumption. In order to communicate with off-chip memories and analogue and RF on traditional PCB-based implementations, Input/Output (I/O) drivers with significant current draw are often required. A single system-on-chip (SoC) makes it possible to remove such power-hungry circuits.     The duty cycle and lifetime energy consumption The other fundamental consideration for designing energy-efficient IIoT sensor nodes is an understanding of the duty cycle and its impact on lifetime energy consumption. Simply minimising the power consumption of individual elements is not enough to guarantee that a remote or  inaccessible sensor can operate on a single battery charge for a decade or more. In such a situation, every microjoule the node requires from its battery is important. But that does not mean the system powered by a typical battery can consume no more than a few microwatts at any point in its life. Such a system would not be able to take measurements and communicate them wirelessly in any practical way. The use of duty-cycle planning makes it possible for the system to perform tasks that take significant amounts of power for short periods, trading those bursts against savings that can be made while much of the system is quiescent. For example, the RF subsystem of a wireless sensor node need only be powered when it is active. This is likely to be one of the most power-hungry parts of the overall design because of the need to supply enough transmitter power to ensure packets of data can be delivered reliably. However, the power consumed by the transmitter portion of the RF subsystem is relatively easy to control. Once a packet has been delivered the transmitter can be shut down. But there can still be significant power drawn by subsystems such as the RF receiver that continue to remain active once the transmitter has finished sending.   The RF receiver often needs to remain active because of timing uncertainty and this type of uncertainty has a major influence on overall energy consumption. Whereas the transmitter has predictable requirements – it need only be activated when data is ready to send – the receiver needs to be active for much longer. It needs to wait for acknowledgments from nodes to which it is sending data, and also needs to activate periodically to be able to listen for unsolicited messages. As a result, the overall energy consumption of the RF receiver will often exceed that of the transmitter over the lifetime of the sensor, even though its instantaneous power demand is lower. An efficient design will exploit power-saving techniques such as putting much of the circuitry into a low-activity state until an RF signal is detected. Another optimisation is to reduce the amount of time per minute the receiver is active at the cost of the sensor node’s responsiveness to external commands.     Although they might appear to be essential to all operations, the microprocessor core and its memory subsystem need careful duty-cycle management because they can demand very high levels of power. The problem for many designs is that software running on the processor is often responsible for core tasks such as fetching data from sensors and passing messages to the RF subsystem. This appears to mandate that the processor be fully active whenever sensor inputs need processing.   However, in many cases, the work performed by the software is very simple. It is quickly checking data values to see if they have passed a limit that might signal a problem, or for increased activity that needs closer inspection. Activating the processor to handle all the data is wasteful and can easily be offloaded to custom hardware or a programmable state machine. These circuits consume far less power and can run independently of the processor, so that and the memory array can be powered down.   Current leakage Even when most of the device is powered down, the power drawn during lengthy periods of sleep can be surprising. Energy lost through current leakage in subsystems that need to remain powered can incur a heavy overhead when analysed over the lifetime of the system because the time the system spends sleeping can be orders of magnitude longer than that during which the system is active. The problem of leakage calls for design techniques that limit leakage in subsystems such as real-time clocks and interrupt controllers to the nanoamp level. It might seem reasonable to disable interrupts for external events and only keep the real-time clock running in some applications. However, in that design the system needs to wake at regular intervals to check inputs that may incur unwanted energy consumption if there is no overall change to record. If the long-term energy usage of an interrupt controller is low enough, keeping that active to respond to events as they happen may make more sense.   When the processor and memory subsystem are powered down, a key decision is how to manage temporary data. One option is to use specialised retention register and memory cells, at the cost of some leakage power. Another is to put important data, such as calibration values, into non-volatile memory (NVM). This allows values to be restored quickly on restart but allows the leakage-prone SRAM arrays and registers to be powered down fully until then. But NVM choices are not always straightforward.   Processes that are optimised for low leakage and that support high-density NVM options may not have the performance required to support efficient RF modules on-chip. The energy needed for I/O drivers that transfer data to an off-chip RF transceiver may outweigh the power savings and security advantages obtained from implementing NVM on-chip. Careful analysis of the application’s requirements will indicate which choice is better for the custom SoC solution.   For the portions of the design that will be active for much of the device’s lifetime, careful attention to detail is required. Seemingly small details such as choosing to multiplex inputs into an analogue-to-digital converter (ADC) will help determine the architecture of choice for those circuits. A sigma-delta ADC may initially appear to offer a good trade-off between accuracy, energy efficiency and silicon area. But it is not suited to multiplexing. Often a successive approximation (SAR) architecture offers superior performance for industrial sensor signals. Advances in SAR design have pushed the energy per bit per conversion down into the range of tens of femtojoules.   Front-end analogue circuits are just as important as the ADC. Amplifiers and buffers that isolate and condition signals before conversion can consume high levels of power and they will be active for long periods of time. Analysis of the specific requirements for bandwidth and accuracy often allow for optimizations that reduce the energy of front-end circuitry and ADCs.   To tie all the subsystems together into a working custom SoC demands the use of power-aware design methodologies to ensure subsystems and circuits are activated properly when required, and can be powered down without disrupting the operation of other parts of the custom IC that need to stay running. Standards such as the Unified Power Format (UPF) have been designed to support such power-aware methodologies, but their application requires experience and attention to detail at different levels of abstraction.   Take an example For example, there may be a logical connection between two subsystems that demands they be active at the same time. But physical restrictions may call for them to form part of a larger power island – an area of the mixed-signal ASIC with a common set of power and ground rails – that includes other subsystems that are not required during that time. Design verification needs to ensure that the entire island is powered up correctly. If not, the final SoC will fail. Such physical design considerations may call for changes to the power-control architecture if the consumption of the whole island is higher than the budget allows. It may call for subsystems to be assigned to different power islands, for example.   Verification also needs to pay attention to on-chip noise, which may point to further optimization of the power-island strategy. For example, a low-noise LDO may be used to power sensitive mixed-signal sections that operate autonomously. Once measurements have been taken or RF communications have been completed, a higher-efficiency DC/DC converter may then be reactivated to analyse incoming data and make decisions.   Although the core requirements of energy efficiency in IIoT sensor nodes are readily understood, as can be seen, the implementation choices are complex and often subtle. Many factors affect the optimum solution for a given IIoT sensor node application, although a custom SoC will frequently be the best target in terms of energy and overall cost. Therefore, the ability to call on the expertise of design teams with extensive experience in custom mixed-signal IC implementation is key to success.  

A New Breakthrough in Battery Technology The breakthrough comes from a team of engineers led by John Goodenough, the co-inventor of the lithium-ion battery. A new discovery has come out which could pave the way for batteries to last more, and it won’t explode. The breakthrough comes from a team of engineers led by John Goodenough, the co-inventor of the lithium-ion battery which is used to power everything from smartphones to electric cars. Led by John Goodenough and a team of engineers, the co-inventor of lithium-ion battery has made this breakthrough. The research was published in Energy and Environmental Science in December and publicized by the University of Texas last week. The research states that in the future a “solid-state” battery design could potentially hold up to three times more energy and charge faster than today’s batteries. The solid-state battery is still in the early stages of development and swaps out one of the essential parts of today’s lithium design—liquid electrolytes—for glass components. The glass electrolytes can store more energy and are much more stable since they prevent the formation of dendrites—metallic projections which grow through liquid electrolyte layers and cause short circuits and explosions. The researchers have stated that the glass electrolytes will allow them to exchange lithium for sodium, which would be cheaper and more eco-friendly option since it can be extracted from seawater. This means the batteries would not just be economical as well, but the will be more powerful than the current batteries we have today. The solid-state batteries can also work in extreme conditions, down to -4 degrees Fahrenheit. This could be a massive breakthrough for car batteries, which obviously have to work through extreme weather. This breakthrough sounds exciting—but it could still be a long way from coming to modern age smartphones. This was just preliminary research, similar to other solid state designs we have seen in the past, so there’s no timetable for when the batteries might actually be applied for practical use, if ever.As super battery started to be used in the works, lithium-ion may be history.  Super battery with supercapacitors“Super” is a popular adjective when it comes to energy storage. Supercapacitors even have it in their name. Now they supposedly make it possible to charge smartphones in seconds and power them for a week. Super! Supercapacitors are already being used in plenty of everyday things as replacements for or supplements to batteries. They power the rear lights on our bicycles when we stop, fill in for interruption-free power supplies in the event of an emergency, prevent data loss in static memories (SRAMs) and provide a brief horsepower boost and save gasoline in racecars by accumulating recovered braking energy. Unlike lithium-ion batteries, they can release and absorb a great deal of energy in a short period of time—hundreds of thousands of times with deep discharging and high currents. However, the storable charge quantity is low. That is why they are still too large and too expensive to be used in smartphone or tablets. The reason that rechargeable batteries and supercapacitors, which are also known as ultra- or double-layer capacitors, have opposing characteristics is the way they store a charge. While this happens in “sluggish” chemical processes such as oxidation, reduction and the storage of molecules or ions in batteries, when it comes to supercapacitors, it generally happens through “swift” charge separation, which is gentle on the electrodes. Ref.KY605-NH50BP-2KY605-BP33-12S-B7   

Microchip’s PIC18F ‘K42’ microcontrollers are available with up to 128kbyte (from 16kbyte) of flash memory in packages from 28-48 pins. Max clock speed is 64Mbit/s and there is up to 1kbyte data EEPROM and 8kbyte of SRAM.   The firm has gone big on its ‘core independent peripherals’ (CIP) to allow functions to be implemented in hardware, saving code, validation time, core overhead, and power consumption, said Microchip. Intended for automotive, industrial control, IoT, medical and white goods, they include peripherals for safety critical applications including cyclic redundancy check with memory scan, a windowed watchdog timer, a 24bit signal measurement timer and a hardware limit timer, as well as up to eight hardware PWMs, complementary waveform generation for power bridges, and multiple communications interfaces. Analogue peripherals including a zero crossing detector, constant current I/O (see below), a comparator, and a 12bit ADC with computation – the latter for automating capacitive voltage division (for touch sensing), averaging, filtering, over-sampling, and threshold comparison. Constant current I/O The constant current I/O feature allows the sink and source current of a pin to be set to 1, 2, 5 or 10mA. This has to be used with caution because the pin circuitry cannot dissipate much static power, so an “external resistor must be inserted in series with the load to dissipate most of the power,” said Microchip. It has an example, with a 5V rail and a load which needs 1mA and whose voltage drop can be between 1.0 and 1.5V. The external resistor and pin circuitry has to make up 3.5-4V difference, so the resistor  needs to be chosen to drop 3.5V at of 1 mA, said Microchip, then the pin can make up the 0-500mV variable difference. A ‘memory access partition’ supports data protection and bootloading, and the ‘device information area’ is a dedicated memory space for factory programmed device ID and peripheral calibration values. Building blocks ADC with computation zero crossing detector 10bit PMW complementary waveform generator numerically controlled oscillator data signal modulator hardware limit timer 24bit signal measurement timer configurable logic cell crc/scan module windowed watchdog timer peripheral pin select direct memory access temperature indicator data signal modulator 5bit DAC UART, SPI, and I2C Ref: KY32-PIC18F1220-E/ML KY0-PIC18F1220-E/SO KY0-PIC18F1220-I/ML

Article provided by University of Illinois at Urbana-ChampaignArticle edit by kynix A new methord to make Green LEDs more brighter and more efficient have been developed by researchers who at the University of lllinois at Urbana Champaign.  Researchers have created gallium nitride(GaN) cubic crystals grown on a silicon substrate that are capable of producing powerful green light for advanced solid-state lighting. "This work is very revolutionary as it paves the way for novel green wavelength emitters that can target advanced solid-state lighting on a scalable CMOS-silicon platform by exploiting the new material, cubic gallium nitride," said Can Bayram, an assistant professor of electrical and computer engineering at Illinois who first began investigating this material while at IBM T.J. Watson Research Center several years ago. "The union of solid-state lighting with sensing (e.g. detection) and networking (e.g. communication) to enable smart (i.e. responsive and adaptive) visible lighting, is further poised to revolutionize how we utilize light. And CMOS-compatible LEDs can facilitate fast, efficient, low-power, and multi-functional technology solutions with less of a footprint and at an ever more affordable device price point for these applications."  GaN was formed ethier hexagonal or cubic typically. HExagonal GaN is thermodynamically stable and is by far the more conventional form of the semiconductor. However, hexagonal GaN is prone to a phenomenon known as polarization, where an internal electric field separates the negatively charged electrons and positively charged holes, preventing them from combining, which, in turn, diminishes the light output efficiency. Until now, the only way researchers were able to make cubic GaN was to use molecular beam epitaxy, a very expensive and slow crystal growth method when compared to the widely used metal-organic chemical vapor deposition (MOCVD) method that Bayram used. Bayram and his graduate student Richard Liu made the cubic GaN by using lithography and isotropic etching to create a U-shaped groove on Si (100). This non-conducting layer essentially served as a boundary that shapes the hexagonal material into cubic form. "Our cubic GaN does not have an internal electric field that separates the charge carriers—the holes and electrons," explained Liu. "So, they can overlap and when that happens, the electrons and holes combine faster to produce light."  At the end, Bayram and Liu still believe their cubic GaN method may lead to LEDs free from the "droop" phenomenon that has plagued the LED industry for years. For LED lighting color like green, blue, or ultra-violet LEDs , their light-emission efficiency declines as more current is injected, which is characterized as "droop." "Our work suggests polarization plays an important role in the droop, pushing the electrons and holes away from each other, particularly under low-injection current densities," said Liu, who was the first author of the paper, ""Maximizing Cubic Phase Gallium Nitride Surface Coverage on Nano-patterned Silicon (100)", appearing Applied Physics Letters. Having better performing green LEDs will open up new avenues for LEDs in general solid-state lighting. For example, these LEDs will provide energy savings by generating white light through a color mixing approach. Other advanced applications include ultra-parallel LED connectivity through phosphor-free green LEDs, underwater communications, and biotechnology such as optogenetics and migraine treatment. Having better performing green LEDs will open up new avenues for LEDs in general solid-state lighting. For example, these LEDs will provide energy savings by generating white light through a color mixing approach. Other advanced applications include ultra-parallel LED connectivity through phosphor-free green LEDs, underwater communications, and biotechnology such as optogenetics and migraine treatment. 

A molecule that transports oxygen in blood could be key to developing the next generation of batteries, and in a way that's environmentally friendly.Lithium-oxygen (Li-O2) batteries have emerged in recent years as a possible successor to lithium-ion batteries—the industry standard for consumer electronics—due to their potential for holding a charge for a very long time. Electronic devices would go for weeks without charging, for instance; electric cars could travel four to five times longer than the current standard.But before this could happen, researchers need to make the Li-O2 batteries efficient enough for commercial application and prevent the formation of lithium peroxide, a solid precipitate that covers the surface of the batteries' oxygen electrodes. One obstacle is finding a catalyst that efficiently facilitates a process known as oxygen evolution reaction, in which lithium oxide products decompose back into lithium ions and oxygen gas.The Yale lab of Andre Taylor, associate professor of chemical and environmental engineering, has identified a molecule known as heme that could function as a better catalyst. The researchers demonstrated that the heme molecule improved the Li-O2 cell function by lowering the amount of energy required to improve the battery's charge/discharge cycle times.The results appear Oct. 19 in Nature Communications. The lead author is Won-Hee Ryu, a former postdoctoral researcher in Taylor's lab, who is now an assistant professor of chemical and biological engineering at Sookmyung Women's University in South Korea.The heme is a molecule that makes up one of the two parts of a hemoglobin, which carries oxygen in the blood of animals. Used in an Li-O2 battery, Ryu explained, the molecule would dissolve into the battery's electrolytes and act as what's known as a redox mediator, which lowers the energy barrier required for the electrochemical reaction to take place."When you breathe in air, the heme molecule absorbs oxygen from the air to your lungs and when you exhale, it transports carbon dioxide back out," Taylor said. "So it has a good binding with oxygen, and we saw this as a way to enhance these promising lithium-air batteries."The researchers added that their discovery could help reduce the amount of animal waste disposal."We're using a biomolecule that traditionally is just wasted," said Taylor. "In the animal products industry, they have to figure out some way to dispose of the blood. Here, we can take the heme molecules from these waste products and use it for renewable energy storage."By using recyclable biowaste as a catalyst material, the technology is both effective and could be preferential in developing green energy applications.Reference:ML-621S/ZTNMS412FE-FL26EMS518SE-FL35E 

Introduction to RF TransistorsIn the world of electronic devices, transistors are one of the most fundamental components, serving as switches or amplifiers in a variety of circuits. Among the many types, RF transistors are specifically designed for handling radio frequency signals, making them essential in wireless communication systems, satellite links, and radar technology. Bipolar Junction Transistors (BJTs) are one of the most common types used in RF applications due to their high current gain and fast switching abilities. Whether you're an engineer, a hobbyist, or someone delving into RF design, understanding BJTs' role in radio frequency (RF) circuits can offer invaluable insights into building effective systems. What is a BJT?Bipolar Junction Transistors (BJTs) are semiconductor devices that consist of three layers of doped material, forming two junctions: an emitter-base junction and a collector-base junction. BJTs are classified into two types: NPN and PNP, which differ based on the polarity of the voltage applied to the junctions. In RF applications, BJTs function primarily as amplifiers. They convert low-power RF signals into higher-power ones, ensuring that the signal can travel longer distances or penetrate through barriers like walls. Their versatility in RF circuits is due to their inherent characteristics, including high frequency response, low noise, and high current handling. The Importance of RF BJTsIn RF circuit design, the right transistor can make a significant difference in the overall performance of the system. BJTs are particularly well-suited for this domain because of their ability to handle high frequencies and maintain stability across a wide range of temperatures. Here’s why BJTs are crucial: High Current Gain (β): In RF circuits, BJTs can amplify weak signals, which is essential in transmitting radio frequencies over large distances without distortion. Frequency Response: RF BJTs operate efficiently at high frequencies, typically in the range of MHz to GHz, making them ideal for applications such as mobile communications, radio broadcasting, and radar systems. Low Noise Performance: Noise is a major concern in RF circuits, especially in communication systems. BJTs are known for their low-noise characteristics, ensuring signal clarity even in noisy environments. Structure and Operation of RF BJTsAt the core of every BJT lies a combination of two p-n junctions. These junctions allow the BJT to operate as a current-controlled device. The primary regions of a BJT include the emitter, base, and collector: Emitter: The region that supplies carriers (electrons in NPN BJTs or holes in PNP BJTs).Base: A thin layer that controls the flow of carriers from the emitter to the collector.Collector: The region that collects carriers from the emitter and allows current to flow through the device.In an RF circuit, the transistor operates in its active mode, where the base-emitter junction is forward-biased, and the base-collector junction is reverse-biased. This configuration allows a small base current to control a larger collector current, achieving the amplification needed in RF applications. The choice between NPN and PNP BJTs often depends on the specific circuit design. NPN BJTs are generally preferred in RF circuits due to their faster switching times and better efficiency at high frequencies. Key Specifications for Choosing an RF BJTSelecting the right BJT for an RF circuit requires careful consideration of several key parameters: Transition Frequency (f_T): This is the frequency at which the current gain of the BJT drops to 1. A high f_T value is crucial for RF applications, as it indicates that the transistor can operate efficiently at high frequencies. Power Dissipation: BJTs can generate significant heat, especially in high-power RF applications. Ensuring that the transistor can dissipate this heat effectively is essential for maintaining performance and longevity. Noise Figure: A low noise figure is critical in RF circuits, particularly in applications like communication receivers where signal clarity is paramount. BJTs with lower noise figures ensure less signal degradation. Collector-Emitter Voltage (V_CE): This rating indicates the maximum voltage that can be applied across the collector-emitter terminals without damaging the transistor. For RF applications, it's essential to choose a BJT that can handle the required voltage range. Current Gain (h_FE or β): The current gain determines how effectively the BJT can amplify the input signal. A higher β value means more amplification, which is particularly useful in RF amplification stages. Real-World Applications of RF BJTsRF BJTs play a vital role in many modern devices that rely on wireless communication. Some of their key applications include: Mobile Communication Systems: In cellular networks, BJTs amplify the radio signals transmitted between the base station and mobile devices, ensuring clear communication even over long distances. Broadcasting: Whether it's AM, FM, or television broadcasting, RF BJTs are used in the transmission of signals to reach a broad audience. Satellite Communication: In satellite uplinks and downlinks, BJTs amplify weak signals from space, allowing them to be clearly received on Earth. Radar Systems: RF BJTs are crucial in radar technology, amplifying the radio waves sent out to detect objects at long distances. RF Power Amplifiers: BJTs are frequently used in RF power amplifiers, which are critical in ensuring that the output signal is strong enough for effective transmission in devices like walkie-talkies, radio transmitters, and microwave communication systems. Design Considerations for RF Circuits Using BJTsWhen designing RF circuits that use BJTs, engineers must account for several design constraints to ensure optimal performance: Impedance Matching: Proper impedance matching between the BJT and other components in the RF circuit is essential to minimize power loss and maximize signal transfer. Stability: BJTs can exhibit unwanted oscillations at high frequencies. Engineers often use techniques like negative feedback or bypass capacitors to improve circuit stability. Thermal Management: Heat dissipation is a major concern in high-power RF circuits. Ensuring that the BJT operates within its safe temperature range is crucial to prevent damage and performance degradation. Biasing: Proper biasing of the BJT ensures that it operates in the correct region of its output characteristic, allowing for stable amplification. ConclusionRF transistors, particularly BJTs, are indispensable components in modern communication systems and other RF applications. Their ability to amplify weak signals, operate at high frequencies, and maintain low noise levels makes them ideal for a wide range of uses, from mobile communication to radar systems. By understanding the key characteristics of RF BJTs, selecting the right components, and designing circuits with care, engineers can create systems that perform efficiently and reliably. Whether you're working on a new RF design or optimizing an existing one, BJTs offer the versatility and performance needed for success.