When examining the multitude of thriving applications that exist for 8-bit microcontroller units (MCUs), certain recurring themes become apparent: low-power consumption, affordability, and simplicity. Whether we are talking about automotive, industrial, medical, or consumer electronic devices, these themes tend to be front and centre. In a world where almost everything is becoming digital and interconnected, it is natural to assume that the simplicity of an 8-bit MCU would limit its applications due to increasing design complexity. However, in many sectors, the push for widespread and distributed intelligence is opening opportunities for effective yet less complicated solutions.

The key to this requirement is, of course, interconnectivity, along with the electronics industry’s ongoing efforts to decrease the size and power consumption of components. Take the example of a smart home, where early devices were predominantly mains powered, had significant localised processing, and usually attempted to incorporate as much functionality as they could while connecting over one of the many communication protocols that emerged.

While there are still many feature packed products that require mains power supplies, the popularity of compact battery-powered Internet of Things (IoT) devices has surged in recent years, fuelled by consumers’ demand for greater distributed intelligence. Devices such as proximity sensors for security and home automation systems and temperature and humidity sensors for intelligent climate control have proved popular. Unlike many earlier IoT devices, these solutions are compact, energy-efficient, and ideally powered by batteries, requiring only minimal processing power. In general, they transfer limited quantities of data to a central hub or the cloud, making them a suitable choice for incorporating 8-bit MCUs in their designs.

The demand for simpler yet widespread solutions that report to a more advanced cloud network is not limited to our homes. Smart cities are another trend on the rise, and low-powered industrial IoT (IIoT) nodes are needed to report data such as air quality, traffic density, and structural health monitoring. Once again, several of these deployment types are well-suited for 8-bit systems, as the effectiveness of the total system relies on a vast coverage, rather than peak processing power. For operators managing these sizable systems that require near-countless nodes, it is vital to reduce any unnecessary overhead, such as component expenses and power usage, as their combined impact can be significant.

The benefits of distributed intelligence are also becoming evident in the realm of smart agriculture. Farming, being a crucial aspect of our livelihood, is, unfortunately, an industry that faces inherent instability due to factors such as extreme weather events, water and fertiliser shortages, and crop diseases, all of which greatly affect a farm’s productivity. The growing demand for dependable and sustainable farming practices that can provide the food we need with fewer resources is fuelling the use of advanced technology.

Traditional farming practices are being revolutionised by the integration of cutting-edge electronics. Implementing networked livestock monitoring systems serves the dual purpose of monitoring herd health and allowing animals more freedom to roam. This in turn improves their welfare and reduces their impact on a specific area. Ultimately, this has a positive impact on the quality of food production.

In a similar manner, the data gathered from agricultural sensor networks is of immense value. It can serve as a guiding light for farmers, empowering them to make informed decisions that foster healthier crops with fewer resources. In the past, determining soil quality required manually collecting samples and conducting either a basic local test or a more accurate analysis in a laboratory. With the advent of smart, battery-powered soil sensors, farmers can now monitor the soil health of their fields in real time. By leveraging this data, farms can implement precise resource management strategies, including optimised water usage and reduced chemical inputs, resulting in enhanced sustainability of their operations.

In the harsh farming environment, 8-bit MCUs are, once again, the perfect choice. Microchip Technology, a leader in the world of MCUs, provides an extensive selection of 8-bit PIC^® and AVR^® MCUs specifically designed to cater to the requirements of rapidly evolving applications like smart cities and intelligent agriculture. These solutions surpass the capabilities of a standard 8-bit MCU and incorporate advanced features, including Core Independent Peripherals (CIPs) and integrated analogue capabilities. As a result, designers can create cutting-edge products with functionality that exceeds that of traditional 8-bit powered solutions.

This ethos of adding functionality to 8-bit MCUs is something core to Microchip’s portfolio and is seen across devices such as the PIC16F18126/46 family. Within these MCUs are Microchip’s Configurable Logic Cell (CLC) peripherals. With an integrated CLC, designers can choose from various basic gates and sequential logic options that can be customised to match the specific logic demands of a wide range of applications. This flexibility enables the creation of custom signals by combining signals, eliminating the need to execute code. The seamless integration of the CLC results in a streamlined design process, lower Bill of Materials (BoM) costs, and enhanced power efficiency, helping to further propagate the deployment of low-power intelligence.

When assessing the current digital landscape, it becomes apparent that interconnected systems will be crucial for our future cities, farms, and homes. However, for these networks to become a reality, a diverse range of solutions is required. This includes both state-of-the-art, high-performance processors and affordable, low-power solutions; the latter is a domain that, for now at least, still belongs to the 8-bit MCU.

By Mark Patrick, Director of Technical Content EMEA, Mouser Electronics

To calculate the input resistance of such a circuit, there’s an equation, namely R_in = R1 * (1 + R3/R2). For the circuit in Figure 1, R_in is the input resistance seen by the power supply, V1. The values of resistors R1-R3 can be chosen based on the application needs.

Resistor multiplier circuits

Resistor multiplier circuits are primarily used to divide a voltage into a fraction of its original value. This is frequently used in power supplies and sensor circuits to establish a stable reference voltage.

They are also used in sensor circuits to scale or attenuate the sensor’s output voltage, which aligns with the input range of a microcontroller or an analogue-to-digital converter. Additionally, resistor multiplier circuits are useful in monitoring battery voltage levels in electronic systems that run on batteries. They trigger alerts or actions when the voltage falls below a certain threshold. In communication systems and audio circuits, resistor multipliers are used to attenuate signals to desired levels with minimal distortion.

In one of my projects, I considered using this particular circuit, but I had concerns about the equation’s accuracy when the power supply voltage decreases during circuit operation. I wondered about the equation’s accuracy and until what supply voltage. Additionally, I also wanted to determine the impact of a declining power supply voltage on the circuit’s performance. Would the circuit maintain the same resistance multiplication ratio at various power supply voltages? That’s why this experiment was set up.

Figure 1: A simple resistance multiplier circuit

The experiment

The circuit shown in Figure 1 was chosen for the experiment due to its simplicity. Although there are various other circuits available, they mainly revolve around the same design and concept.

During the experiment, various power supply voltages were applied, and at each step the circuit’s resistance was calculated using the input voltage and current. The applied voltage ranged from 1Vdc to 20Vdc, which is the operating range of the LT 1012 op-amp. All remaining components were kept unchanged.

The measured circuit input resistance was then plotted; see Figure 2. The curve reveals that the relationship between the power supply voltage and the circuit input resistance is not constant, which departs from the R_in = R1 * (1 + R3/R2) equation. This equation only holds true at a single point on the curve, when the supply voltage is at 13.4Vdc. When the voltage falls below or rises above this 13.4Vdc point, the circuit shows higher and lower resistances.

Also, another observation was made: The curve in Figure 2 shows a linear relationship between the power supply voltage and circuit resistance changes, at a linear ratio of about 82.3Ω/Vdc.

Figure 2: Circuit input resistance vs power supply voltage

This leads us to conclude that the resistance multiplier circuit in Figure 1 doesn’t provide a constant resistance multiplication ratio as per the commonly-used equation R_in = R1 * (1 + R3/R2).

From the above, a new equation arises, namely R_in = 82.3 * R1 * (1 + R3/R2), which describes the resistance multiplier performance more accurately. This experiment and its findings are significant for circuit designers, considering this circuit’s wide implementation. Understanding the impact of the power supply voltage impact on circuit performance is crucial, helping designers to create more accurate circuits.#

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Consumer electronics is a dynamic and competitive industry, where consumer demand and expectations are constantly changing and evolving. Consumers want products that are smart, connected, convenient, and feature-rich but also affordable and energy efficient. So, how can designers of consumer electronics meet these expectations and deliver products that satisfy the market needs?

Their main focus is to meticulously balance the functionality of components and the performance of the system, ensuring that design goals are achieved and leaving room for future evolution. However, devices, particularly those powered by batteries, cannot incorporate excessively complicated components with unnecessary features if they want to operate effectively and be competitively priced.

Furthermore, the challenge is compounded by the dynamic nature of the consumer electronics market. Few markets experience as rapid evolution and iteration as the consumer device industry, with leading manufacturers frequently introducing new smartphones and smart home devices on an annual basis. Design engineers are faced with the need for components that are easy to integrate, supported by reliable manufacturing, and capable of adapting to evolving designs. Additionally, if component replacement is necessary, minimal redesign should be required, both in terms of electronics and coding.

With the constant evolution of the electronics industry, 8-bit microcontroller units (MCUs) have become an essential solution in this dynamic environment, offering unparalleled flexibility and versatility to meet the ever-increasing demands of the market. The hallmark of 8-bit MCUs is characterised by their simplicity, ease of integration, and ability to enable designers to quickly develop and incorporate new features into their designs. For example, whether a design upgrade involves enhancing a smart home device by adding new interfacing options or optimising the functionality of a fitness tracker, 8-bit MCUs provide the agility needed to stay ahead in a competitive market, offering reduced development cycles compared to their more powerful 16- and 32-bit counterparts.

Even if the system requirements remain unchanged, there are numerous advantages to adopting the 8-bit philosophy of ‘less is more,’ as long as the MCU adequately supports the desired applications. When it comes to the consumer market, one of the key aspects to consider is the portability of electronics. In this regard, battery life plays a critical role. It is essential to have extended usage without the need for frequent recharging—especially for applications like wearables and media devices—as it directly impacts user convenience and even the core functionality of these devices.

The exceptional low-power operation of 8-bit MCUs truly shines in this context, as it enables optimal battery efficiency while still delivering impressive performance. The energy-efficient nature of 8-bit MCUs, whether used in wearable gadgets or handheld devices, significantly improves the overall user experience by extending the lifespan of batteries and reducing downtime.

In today’s age, where consumer electronics adoption is driven by affordability and accessibility, the need for cost-effective solutions cannot be overstated. Eight-bit MCUs provide an attractive value proposition by offering impressive performance levels while being significantly more affordable and simpler to develop than their higher-bit counterparts. The affordability of 8-bit MCUs, especially at scale, enables manufacturers to produce innovative products without inflating price tags, democratising access to cutting-edge technology.

Microchip Technology, a leader in MCUs, provides an extensive selection of 8-bit PIC^® and AVR^® MCUs that are specifically designed to cater to the varied requirements of consumer devices. These solutions go beyond a basic 8-bit MCU and incorporate advanced features such as Core-Independent Peripherals (CIPs) and integrated analogue capabilities, giving designers the power to develop cutting-edge products that resonate with consumers.

The PIC16F171 MCU bolsters its core functionality by integrating several key features designed specifically for consumer electronics applications like white goods and smart IoT devices. These features include a low-noise operational amplifier (op-amp), a 12-bit differential analogue-to-digital converter with computation (ADCC), two 8-bit digital-to-analogue converters (DACs), and a 16-bit pulse-width modulation (PWM) module amongst other features typically deployed separately to the MCU in consumer electronics.

The PIC16F180XX family of MCUs is ideal for cost-effective sensor and real-time control applications, such as portable consumer electronics. These devices integrate a 10-bit ADCC, automated capacitive voltage divider (CVD) techniques for advanced capacitive touch sensing, as well as an 8-bit DAC and PWM module. To support the rapid rate of development needed in the consumer electronics market, Microchip also offers a comprehensive software ecosystem, which includes a variety of plug-ins and tools.

Whether it’s designing sleek wearable devices or revolutionising home automation systems, 8-bit MCUs can serve as the backbone of modern consumer electronics. Their simplicity, affordability, and power efficiency make them indispensable tools for engineers striving to deliver next-generation solutions in a rapidly evolving landscape.

As a result, medical care has undergone a transformative shift, granting individuals greater autonomy in monitoring and maintaining their health. With the help of modern wearables and health trackers such as smartwatches, fitness bands, and glucose monitors, for the first time in history, people can continuously measure and track their vital signs, activity levels, and other biometrics without visiting a doctor or hospital. Any data captured by such devices can then be shared wirelessly with healthcare professionals via a centralised database, providing them with real-time insights into a patient’s condition and enabling timely interventions if needed.

The IoMT has also opened new possibilities for personalised and preventive medicine as well as telemedicine and home care. By leveraging the power of large data analytics and artificial intelligence, digitised healthcare can help identify patterns, trends, and anomalies in a patient’s health and provide tailored recommendations and feedback. Technology can also be utilised through remote consultations and examinations, which can reduce the need for physical contact and travel and ultimately enhance convenience and safety for patients and providers.

Continual advancements in technology are allowing engineers to leverage faster wireless connectivity and create devices with greater processing power, storage, and sensing functionality. Apart from the familiar fitness watches, a plethora of wearables like rings and smart clothing have hit the market. These cutting-edge gadgets offer an extensive range of medical services, from tracking fitness and monitoring vital signs to detecting early stages of cancer.^[1]

However, smart medical devices can pose significant design challenges for engineers and developers, who need to ensure that the devices are reliable, secure, and efficient. Personal IoMT devices must be able to perform complex functions such as sensing, processing, and communicating biometric data while consuming minimal power and space. Additionally, since these devices are meant to engage with us, they are typically designed to be ergonomic, battery-powered, and wearable, which requires them to be lightweight, compact, and long-lasting. For designers of such products, it is usually a case of carefully balancing form and functionality.

A common approach to meeting these requirements in intelligent medical devices is to incorporate 8-bit microcontroller units (MCUs) into their core components. The reason why 8-bit PIC^® and AVR^® MCUs are so advantageous for medical devices is that they allow for effortless customisation of onboard hardware with minimal overhead, providing a desirable blend of performance capabilities and power efficiency. As a result, they enable the production of products that achieve incredible system efficiency without compromising on performance or costs.

Microchip Technology, a prominent company in the field of 8-bit MCUs, has been designing and manufacturing 8-bit PIC and AVR MCUs since the 1970s. Similar to their tailored automotive offerings, Microchip’s 8-bit MCUs offer several advantages specifically for IoMT and wider medical applications.

Microchip offers a variety of wireless modules and transceivers that can be seamlessly connected to their 8-bit MCUs, simplifying design considerations and enhancing system integration, making them ideal for compact wearable devices with limited space. Another key aspect of Microchip’s PIC and AVR solutions is the integration of on-chip Core Independent Peripherals (CIPs) which enhance versatility and provide a distinctive level of configurability to the market. By utilising CIPs, engineers can create efficient programs with minimal code overhead, design compact packaging, and decrease the overall cost of their bill of materials (BOM), all of which are essential for the success of wearable technology.

Microchip’s 8-bit MCUs are unique in that they do not impose any restrictions on customers who want to use their parts in devices that conform to the US Food and Drug Administration (FDA) Class I, II, or III medical device regulations. This flexibility allows customers to select the most suitable solution for their specific requirements. Development of Microchip 8-bit solutions is further simplified with the Microchip MPLAB PICkit 5 In-Circuit Debugger/Programmer. The kit, when used with the MPLAB X integrated development environment (IDE), offers a user-friendly graphical user interface (GUI) that facilitates rapid prototyping and portable programming for Microchip components such as PIC, dsPIC^®, AVR, and SAM (Arm^®) devices.

By utilising efficient 8-bit MCUs, the IoMT can thrive, offering increased benefits and possibilities for the medical industry and society. By incorporating intelligence into medical devices and making them accessible to users, we can empower individuals with the ability to take control of their healthcare. The simplicity and efficiency of 8-bit MCUs combined with the intelligence and connectivity of the IoMT enable engineers and developers to create revolutionary and meaningful solutions that have the potential to enhance the health and well-being of millions of people worldwide.

^[1] https://news.mit.edu/2023/wearable-ultrasound-scanner-breast-cancer-0728

By Mark Patrick, Director of Technical Content EMEA, Mouser Electronics

Within automotive design, some initiatives are persistent across every model and manufacturer. First is the obvious shift away from fossil-fuel-powered internal combustion engines to sustainable electric vehicles (EVs), and the second is the rise in automotive intelligence. Looking to increase the functionality and safety of their vehicles, in the hope of providing a competitive edge in a busy market, more OEMs are adding advanced driver-assistance system (ADAS) functions as well as greater infotainment and driver convenience features.

Similarly, the industry is actively transitioning from powering automotive subsystems with mechanical solutions to using networked electronic solutions to support greater system electrification, intelligence, and efficiency. As a result, modern vehicles have evolved to the point where they are now essentially data centres on wheels, with every area of the vehicle continuously capturing or processing small frames of data. But data and sophisticated control can come at a cost, beyond monetary terms. With a vehicle’s weight severely impacting performance and range, manufacturers have to be smart about their system architecture. Connecting endless vehicle subsystems, ranging from chassis control modules to motorised mirror drivers to centralised processing systems, would significantly impact vehicle performance, adding hundreds of kilos of wiring looms into already tightly packaged designs.

The alternative approach is to implement a zonal architecture, in which systems are organised based on the specific area of the vehicle they occupy rather than their functionality. This enables data processing and some decision-making to be kept localised, handled by smaller MCUs at the edge of the vehicle’s architecture, as opposed to centralised body domain controllers (BDCs). This reduces the need for extensive wiring connecting back to central processing systems. The shift in design ethos, coupled with a greater dependence on electronically controlled functions (as opposed to mechanical ones), has resulted in a substantial increase in the need for MCUs that can provide convenient, cost-effective, and dependable integration and operation.

Upon closer examination of any vehicle zone or module, it becomes evident that MCUs serve as a fundamental component, providing control of peripheral functions and sensors without adding significant complexity or overhead to the vehicle’s architecture. MCUs are used to govern systems such as seat controls, in-vehicle and exterior lighting, mirror and side-mirror control, steering wheel controls, switchgear, capacitive controls, and much more.

Yet, even with the abundance of MCUs to choose from to control these modules, why are 8-bit Microchip Technology PIC and AVR MCU models often considered the most advantageous option? One of the main reasons for this preference for vehicle subsystems is their simplicity and efficiency. Their focus is on delivering the necessary functionality while ensuring the design is simple and lightweight and minimises power consumption. For many vehicle subsystems, even those deemed ‘intelligent’, the level of control and processing needed is relatively basic, and they do not need the level of functionality seen with 16-bit and 32-bit microprocessors.

Instead, many automotive OEMs are turning to solutions like PIC and AVR MCUs from Microchip Technology, which are essentially an extension of a typical 8-bit microprocessor. At the core is the same low-cost and low-power performance expected, with simple system integration and programming but with an added range of additional features and Microchip’s Core Independent Peripherals (CIPs) tailored to the market’s precise requirements.

Microchip’s latest PIC and AVR solutions come with features such as an integrated ADC and flash memory as well as automotive-qualified models with on-board controller area network (CAN) bus to allow for easier communication between vehicle systems without the need for external hardware. Furthermore, they have been designed to ensure reliable performance in harsh automotive environments, providing off-the-shelf compliance with the latest rigorous safety standards required by the automotive industry.

By taking what is, in comparative terms, a very simple electronic component and integrating key additional functionality, electronics manufacturers can create devices that are of real value to the automotive industry. With modern vehicle makers seeking greater system intelligence and moving to zonal distribution, there is now a bigger demand than ever for low-powered MCUs. In essence, MCUs have now become a fundamental automotive component. While 16- and 32-bit microprocessors will have their place, 8-bit variants—with their low cost and low complexity—are arguably best suited to fill a large number of core vehicle applications.

By Mark Patrick, Director of Technical Content EMEA, Mouser Electronics

Across the industrial sector, widespread electrification and digitisation are transforming a wide array of operations and processes. Traditional factories and production plants are a significant part of this segment, where automation and robotics play a crucial role in enhancing efficiency and productivity. However, the industrial sector also includes a diverse range of other facilities, including offices, distribution hubs, and research facilities.

Modern industrial organisations increasingly rely on digital technologies for functions like remote monitoring, predictive maintenance, and energy management. For instance, advanced sensors and data analytics are typically employed to optimise production processes, monitor equipment performance, and detect potential issues in real time. Additionally, the industrial sector is adopting advanced overarching solutions like the Industrial Internet of Things (IIoT) and artificial intelligence (AI), which rely on intelligent systems.

But with such diverse applications, the industrial sector necessitates tailored solutions to meet its specific needs, driving the demand for innovative intelligent technologies and digital solutions. Just like in the automotive industry, industrial systems also exhibit incredible scale and complexity. This demands the creation of architectures that rely on vast networks of interconnected but individual modules—rather than a singular system—to handle the required functionality.

As an illustration, let’s consider a scenario where a production line comprises numerous automation and safety elements as well as sensor nodes distributed across the entire building. These elements are responsible for continuous safe operation and need to be managed in real time with the data collected and processed before being relayed back to a central control unit. By employing this architecture, the complexity is significantly reduced and scalability is greatly improved, enabling the creation of large-scale industrial solutions. To fulfil the functionality of this system, each edge sensor node must have its own microcontroller unit (MCU). These can provide intelligent operation at the edge while seamlessly communicating vital information between the sensors and overall control systems as required.

In large-scale industrial applications, the advantage of using a networked approach with an MCU in the edge node goes beyond reducing the workload of the central processor. It also allows for better optimisation of data transfer over the network. By having each node controlled by a single MCU, data can be processed and filtered at the edge before being sent to the central processor. This intelligent data reduction significantly reduces the amount of data that needs to be transferred, resulting in improved network efficiency.

For engineers, the challenge in designing these systems lies in the sheer scale of industrial settings. With potentially thousands of individual modules within a single building, the cost and complexity of operating such a system can quickly become overwhelming, leading to increased production and maintenance costs. This is where 8-bit MCUs can prove to be invaluable. Unlike their more powerful and complex counterparts, 8-bit MCUs are better suited to provide exactly the functionality required for the task at hand; as with any project, the last thing you want to do is pay for unnecessary functionality. Such 8-bit MCU solutions help to minimise redundant overheads, resulting in more streamlined and cost-effective solutions.

With a single 8-bit MCU, the savings might be minor; but in the context of large-scale industrial applications, the combined reductions that 8-bit MCUs enable are exponentially magnified. They allow for the deployment of numerous nodes without incurring excessive costs or power consumption. The principle of ‘less is more’ also offers advantages for the ongoing maintenance, diagnostics, and fault-finding processes. Subsystems that are broken down and utilise straightforward yet efficient 8-bit MCUs are theoretically easier to handle compared with larger centralised systems that rely on more advanced control networks.

But not all 8-bit MCUs are made equally. When choosing microcontrollers for industrial applications, it is important to consider various key design requirements, such as speed, complexity, peripherals, and flash memory, in relation to your design. Given an 8-bit MCU within an industrial setting could be installed with systems ranging from production-line automations to office heating, ventilation, and air conditioning (HVAC), engineers need a wide range of options and careful selection to optimise their design.

This is something Microchip Technology engineers have kept in mind when developing the company’s . The company’s product range encompasses a wide array of solutions, catering to the unique industrial requirements of its customers’ applications. This includes rugged and reliable 8-bit solutions tailored for industrial settings, as well as devices like the innovative , which meets IEC 60730 Class B library (UL certified) and ISO 26262 FMEDA functional safety.

Industrial design is far from being a straightforward field: The term itself encompasses a wide array of sectors, systems, and functions, illustrating the discipline’s complexity. While engineers working on industrial demands may have wildly different priorities and considerations, there are still many shared factors. Achieving goals like simplifying the system’s architecture, reducing energy consumption, and lowering costs is a top priority for all engineers, and to accomplish these objectives, many engineers will rely on 8-bit MCUs, especially as their designs expand and they require distributed intelligence.

By Mark Patrick, Director Technical Content EMEA, Mouser Electronics

The circuit shown in Figure 1 represents a typical annunciator circuit, widely used due to its simplicity and ease of construction. It is designed to activate an audible alarm through a speaker or buzzer, shown as R5 in the figure. Figure 2 shows the waveform generated by the circuit.

It is important to ensure the reliability and functionality of these circuits under all possible circumstances, including when power supply voltage begins to decay.

This experiment should show us the limitations of the annunciator circuit when the power supply voltage drops below the standard 5V.

Figure 1: A popular annunciator circuit

Figure 2: Current passing through the speaker or buzzer

The experiment

We used the circuit shown in Figure 1 for the experiment, and applied a range of voltages to it, with the peak-to-peak output current passing through the speaker, R5. All the monitored current peak-to-peak values were plotted against each applied voltage, which was varied from 0Vdc to 15Vdc in 1Vdc steps; see Figure 3. All electronic components were kept fixed throughout this experiment.

Figure 3 shows that the circuit is very stable at the higher end of the power supply range, specifically when it exceeds 5Vdc, up to 15Vdc. However, when the voltage decreases, the situation changes: Below 7Vdc, the circuit’s output starts to decline significantly. At 4Vdc, the circuit stops functioning, with no output observed.

Figure 3: Peak-to-peak output current passing through the speaker

This finding is important when building circuits, to ensure the power supply is higher than 5Vdc, otherwise this circuit won’t be reliable and its proper functioning will be compromised.

By Dr Sulaiman Algharbi Alsayed, Managing Director, Smart PCB Solutions

On to 32-but MCUs?

Since the 1970s, 8-bit MCUs have been widely used in consumer and industrial applications, and most analysts forecast that we will see their continuous growth well into the next decade. Today these devices are even smarter and more capable than ever, finding place in nearly every system – from automotive and industrial to consumer and medical.

Naturally, we’d assume that an increase in distributed intelligence in smart devices and systems would be better served by 32-bit MCUs, but let’s not be so hasty. The bit size in an MCU is important, but there are also other factors to consider. Today’s 8-bit MCUs are a lot more powerful and sophisticated, and can easily cater for modern applications. In fact, they are often the best solution for systems that need compactness, cost-effectiveness and energy efficiency. They are also advantageous in applications that require substantial computational power and many peripherals. As co-processors they effectively off-load tasks from central processors, for system efficiency. For example, 8-bit MCUs can be used to pre-process analogue signals in sensor nodes, reducing the amount of data sent to the central processor.

Wide-range applications

In automotive, distributed intelligence has experienced a remarkable surge, resulting in smarter and more advanced vehicles. A significant factor behind this increase in functionality is the industry’s move from mechanical-based subsystems to networked electrical set-ups.

Modern vehicles consist of many individual subsystems or zones, interconnected and overseen by larger electronic control units (ECUs). At the heart of any subsystem are MCUs, controlling individual functions and modules such as lights, actuators, power fold mirrors, steering wheel buttons, switchgear – to name just a few. Using 8-bit MCUs to control these peripherals can reduce system overheads and complexity, by allowing localised processing and basic decision making, as well as removing the need to relay everything back to the ECU. Although there are many MCU options to power these modules, 8-bit MCUs are often the best choice.

The demand for 8-bit MCUs is fuelled by distributed intelligence in industrial applications also. Having an MCU in a networked edge node minimises the volume of data that is shifted across the network, reducing bandwidth requirements and the central processor’s workload. For example, instead of connecting several sensors to a single central processor, a much more efficient way is to add a small and cost-effective 8-bit MCU at each node, enabling communication with the main processor only when necessary.

Without this modular approach, many modern automation and robotic applications simply wouldn’t be possible. The sheer volume of data produced by motors, actuators and sensors can lead to unworkable network traffic, incredibly complex code and drastically increased demands on the central processor. Equally, from a design standpoint, because industrial applications can be very diverse in function and large in scale, engineers must treat individual functions as unique modules.

Beyond industry and automotive applications, 8-bit MCUs are also seeing an increased demand in the Internet of Things (IoT) and the Internet of Medical Things (IoMT). Whether we are talking about modern wearables and health trackers or thermostats and smart speakers, all solutions are reliant on data collection, intelligence and wireless communication, whilst demanding low-power operation.

What is clear from talking to electronic engineers and manufacturers like Microchip is that not only is the decline of 8-bit MCUs far from imminent, but there will probably be novel 8-bit offerings to emerge yet.

Microchip’s MCUs

One company synonymous with 8-bit microcontrollers is Microchip Technology, having released its first 8-bit MCU in 1976 – the PIC1650. Microchip’s 8-bit MCU portfolio has significantly expanded since then, with added functionality and abilities, allowing more systems to make the most of PIC and AVR MCUs, including the PIC16F171 (Figure 1) and AVR64DD32/28 ranges. These ranges feature on-chip Core Independent Peripherals (CIPs) and integrated advanced analogue processing, making designs more efficient and requiring lower power. The inclusion of CIPs and common analogue modules offer further versatility and a unique level of configurability to system designers, allowing the development of efficient programs with minimal code overhead, and to create designs with compact packaging, with lower overall bill of materials.

The simplicity and efficiency of 8-bit PIC and AVR MCUs make them preferred in vehicle subsystems, keeping the designs compact, and providing the low-power operation that is often sought in modern electric vehicle applications. Microchip has further tailored its solutions for the automotive market by integrating a Controller Area Network (CAN) bus into its automotive 8-bit microcontroller range.

By Mark Patrick, Technical Content Director, Mouser Electronics

The circuit in Figure 1 shows a simple composite amplifier that works to 300MHz. I tested the circuit at a DC offset voltage of 1-15V DC in combination with an input AC signal and found it very stable. The circuit continues to provide stable output regardless of the input DC offset voltage, which is great.

The next step was to check the circuit’s capability to handle a low output resistance load. I tried to identify the lowest connected output load resistance that can take the circuit out of its nominal performance. This would help me determine if the circuit remains stable at extremely low resistance loads.

Figure 1: A typical composite amplifier circuit

Figure 2: The circuit’s output at 1Vdc and 40MHz

The experiment

For simplicity I used the circuit of Figure 1 for the experiment, although many other types of composite amplifiers exist. A range of output resistance was connected to its output, and its output signal peak-to-peak voltage measured, which was then plotted against each output load resistance value.

All electronic components were kept fixed throughout the experiment, except for output resistor, R6. The power supply for the op-amp HA-2539 was kept at ±15V DC. The input signal’s frequency was fixed at 40kHz, a value that was selected after noticing the circuit’s stable performance. The op-amp HA-2539 has a wide frequency bandwidth and the input signal amplitude was fixed at 1V DC.

During the experiment, I changed the load resistances between 1Ω and 30Ω.

Results

The results of the experiment are shown in Figure 3. It can be seen that the circuit exhibits great stability even at varying output load resistances. A discernible decline in the output signal’s peak-to-peak value is only noted when the output load resistance drops below the threshold of 2Ω.

Figure 3: Output signal peak-to-peak voltage vs. load resistance

This means that this circuit shows great stability across a wide range of output load resistances. This is a positive finding for circuit designers, who should note this circuit’s slight limitation when connected to low-resistance loads.

Furthermore, it is worth noting that the circuit’s stability under varying load conditions highlights its reliability and suitability for a wide array of applications.

Although this could be a no-go for personal flying vehicles, it is achievable for urban air taxi services, which will fly set routes, for which range is calculated, with added margin for safety.

Volocopter is a German electric vertical take-off/landing (eVTOL) aircraft maker, which claims it has completed over 1500 flight tests for its VoloCity urban air taxi; see Figure 1. VoloCity has 18 rotors and nine lithium-ion (Li-ion) battery packs, each powering two rotors, which adds redundancy for failsafe assurance. Any unexpectedly rapid discharge of a single battery pack, or failure of an individual motor or inverter, will leave enough power for the multicopter to make urgent yet safe landing.

Figure 1: VoloCity by Volocopter

 The battery packs are exchangeable, cutting down on turnaround time in getting the vehicle back in the air with a full charge.

According to the manufacturer’s data, the empty vehicle weighs 700kg and has a maximum take-off weight of 900kg. This is enough to carry two passengers with baggage, says Volocopter, with a maximum flying range of 35km.

In a 2021 feasibility study, the UK Civil Aviation Authority analysed a theoretical air taxi service between Heathrow Airport and London City Airport. The direct aerial distance between the two destinations is about 24km, so the VoloCity could theoretically make the trip without stopping and still have nearly 50% range left. This suggests that technological capabilities are already good enough to support useful commercial services, although planners must consider the effects of airspace restrictions, emergency detours, adverse weather conditions and other factors. Making a stop on the way to exchange the battery may be an option if needed, although future generations of vehicles can be expected to fly farther.

Technological improvements

The automotive industry continues to increase the performance and driving range of electric vehicles by improving multiple aspects of their architecture, including battery technology, battery management and monitoring, and power electronics. Makers of urban air mobility (UAM) vehicles can find improvements in the same areas.

Battery technology

Batteries with high energy density are crucial to maximise range and endurance without compromising on payload capacity. Currently, Li-ion is the battery of choice, although the technology is approaching maturity, therefore its limitations.

Among the alternatives, supercapacitors could have a role, as might solid-state and lithium-sulphur batteries, which promise greater energy density and safety and lower lifecycle costs.

Battery management and monitoring

Better battery management can extend flying range through more accurate state-of-charge and state-of-health monitoring, with cell balancing to maintain capacity and efficiency. At the same time, ensuring battery safety is paramount and requires proper protection and effective and lightweight thermal management.

Power electronics

In the power electronics domain, wide-bandgap semiconductors can offer the same advantages in UAM vehicles as in roadgoing EVs. These include greater switching efficiency that allows increased operating frequency, smaller size in relation to voltage rating, tolerance for higher operating temperatures and better reliability. Raising the operating frequency allows the use of smaller passive components in the power supply circuitry, which can reduce module size and weight. Tolerance for increased operating temperature can permit simplified thermal management, leading to further weight savings.

Additionally, integration and overall system optimisation are essential for electric UAM vehicles, to balance the interplay between battery technology, motor technology, battery management and power electronics for better performance and safety.

Equally important to consider is the time to battery end-of-life, to avoid excessive degradation whilst in service. Disposal of retired batteries must be handled properly; perhaps a second life beckons in grid-connected storage, as already suggested for EV batteries.

Market development

Meanwhile, regulators are getting ready. The European Union Aviation Safety Agency claimed a world first in 2022 by proposing its regulatory framework for eVTOL services like air taxis. The framework covers aspects including airworthiness, air operation, flight crew licensing, and the rules of the air.

Forecasters see a vibrant future for UAM. Some operators want to start commercial air taxi services in major European cities by 2024. Market analyst house McKinsey sees the biggest operators handling some 20,000 flights per day by 2030, with the typical average flight lasting about 18 minutes.

By Mark Patrick, Director of Technical Content, Mouser Electronics

The circuit works as follows: The TTL chip is a voltage comparator, which compares the input voltage with the Zener voltage. When the input voltage drops below that of the Zener, the TTL output goes high, turning the speaker on. When the input voltage stays above the Zener voltage, the TTL chip output goes low, which turns off the speaker.

A beneficial feature of this circuit is that it draws extremely low current in standby mode, i.e., when the input voltage is higher the Zener voltage, or 144µA. This makes it suitable for many applications where power consumption is a concern, such as battery-powered devices. For example:

• In battery-powered devices the circuit monitors the battery voltage and sounds an alarm if the voltage drops below a certain level.
• In security systems the circuit can monitor a break-in or another security event.
• In industrial applications the circuit can monitor the voltage of a power supply or other electrical system.

Figure 1: A typical TTL-based low-power alarm circuit

Figure 2 shows this circuit’s performance, with the x axis representing the input voltage and the y axis the current passing through the 100-ohm speaker. Threshold voltage is the voltage at which the current through the speaker begins to increase significantly. In our case this is around 5Vdc, which is the nominal voltage of the Zener diode.

When the input voltage is below 5Vdc, the current passing through the speaker goes high, operating the speaker; above 5Vdc this current is very small. In our case, the maximum current that flows through the speaker is around 144µA.

Figure 2: The current passing through the speaker

TTL is a type of logic gate that operates at a supply voltage of 5Vdc. If the power supply voltage goes above or below this level, the circuit’s performance will change, too. Standby current is the current that flows through the circuit when it is not actively doing anything. The standby current of a TTL circuit is typically very low – in the microampere range.

Experiment setup and results

Questions relating to this circuit and its performance include:

• What happens if the power supply voltage (5Vdc) drops or rises?
• What will the standby current be?
• Will the circuit still be stable?

Since this circuit is commonly found in many applications, it is very important to determine the answers to these questions, so we set up the following experiment.

We check the circuit’s performance for several power supply voltages – 3Vdc, 4Vdc, 5Vdc, 6Vdc and 7Vdc. For each one we plot the magnitude of the current passing through the speaker, but also the standby current (when the input voltage above 5Vdc) vs. the power supply voltage (4-7Vdc).

We used a 5Vdc Zener diode; different Zener diodes can be used for threshold voltages different to 5Vdc.

We also assumed the following:

• All circuit component’s values were kept unchanged.
• The ambient temperature was kept at 25^o

The resulting plots from the experiment are shown in Figures 3-4.

Figure 3: The speaker current vs. the input voltage at various power supply voltage levels

Figure 4: Speaker current vs. power supply  voltage

These results show that our circuit in Figure 1 draws very low current when in standby mode, or 5Vdc power supply voltage, i.e., in this mode it draws only 144µA. However, the experiment also shows that the circuit draws very high current (in standby mode) when the power supply voltage deviates from the nominal 5Vdc; see Figure 4.

This finding is very important for circuit designers to consider, since they must be aware of this circuit’s limitations. A circuit designer will then either use a stable or regulated power supply to support this circuit or consider using a different design if low power consumption is crucial for the application.

By Dr Sulaiman Algharbi Alsayed, Managing Director, Smart PCB Solutions

Applications

The peak detector circuit is a non-linear circuit, which means that its output is not a linear function of the input – which can be disadvantageous in some applications.

This circuit is suitable for detecting peak amplitudes of an audio signal, useful for normalising the signal, or for compression or limiting. The circuit can also be used to demodulate a radio signal or for automatic gain control. In power supplies, the peak detector can monitor the peak voltage, to protect from overvoltage conditions.

Figure 1 shows a simple peak detector circuit, which consists of an op-amp, two resistors and a capacitor. Here we will try to determine how the circuit behaves at various input signal frequencies.

Figure 1: A typical peak detector circuit

Experiment setup

The input signal to the circuit for our experiment is 1V DC, with the input frequency varied from 5kHz to 100kHz in 5kHz increments. The output signal’s amplitude was measured at each step, and plotted; see Figure 2.

For the experiment, we assumed the following:

• All circuit components were kept unchanged.
• The ambient temperature is static at 25^o
• The power supply voltage is kept at 9Vdc.

Figure 2: Output signal amplitude vs. input signal frequency

From Figure 2 we can determine the following:

Unstable performance

The peak detector circuit does not deliver a stable output voltage, similar to the input signal voltage. The output voltage only matches the input voltage at momentarily, at a specific frequency. For example, when the input signal is at 5kHz or 50kHz, the output voltage will match it. However, any slight change in the input signal voltage will rise of lower the output voltage compared to the input.

Amplification effect:

When the input signal frequency is between 5kHz and 50kHz, the peak detector circuit delivers an output signal with a magnitude higher than that of the input signal. This amplification effect is clearly seen in Figure 2; it is at its highest when the input signal frequency is 25kHz.

 Attenuation affect:

In contrast to the amplification effect, the peak detector circuit delivers an output voltage lower than the input signal when the input signal’s frequency is above 50kHz. The output signal amplitude is reduced exponentially, as seen in Figure 2.

Based on these results, it can be concluded that this peak detection circuit can’t deliver a stable output voltage when the input signal frequency changes. The output signal is similar to the input only at specific input frequencies, 5kHz and 50kHz. This makes the circuit’s use limited to applications where the input signal frequency is very stable.

Also, the circuit amplifies and attenuates the input signal based on the input frequency: it amplifies it when the frequency is between 5kHz and 50kHz, but attenuates it when it rises above that level.

These findings are very important for electronic circuit designers to know, since they must be fully aware of this circuit’s amplification and attenuation effects at various input frequencies. It is also important to be aware of this circuit’s frequency instability when the input signal frequency is not fixed.

By Dr Sulaiman Algharbi Alsayed, Managing Director, Smart PCB Solutions