A review of the five critical conditions that influence power scheme design provides a practical, step-by-step guide to help engineers confidently integrate power management integrated circuits (PMICs) into their SoC-based systems.
Introduction
As embedded systems evolve to control more demanding applications, ranging from edge AI to advanced connectivity and multimedia processing, designers are increasingly turning to system-on-a-chip (SoC) solutions. These highly integrated devices offer significant performance and functionality advantages over traditional microcontrollers, but they also introduce new design complexities, particularly in the area of power management.
Unlike simpler microcontrollers, which often require a single supply voltage, SoCs typically need multiple power rails, each with specific voltage levels, current capacities, sequencing requirements, and timing constraints. Failure to meet these requirements can result in unreliable operation, reduced performance, or even permanent damage to the device.
What is a System-on-a-Chip (SoC)?
A SoC is an integrated circuit that consolidates all the essential components of a computer or electronic system onto a single chip. This includes the central processing unit (CPU), graphics processing unit (GPU), memory controllers, input/output (I/O) interfaces, and often specialized modules such as those used for digital signal processing (DSP), AI accelerators, and wireless communication units (Wi-Fi, Bluetooth®, LTE/5G). The goal of an SoC is to deliver high performance and functionality in a compact and energy-efficient form factor, making it ideal for mobile and embedded applications.
SoC development began in the late 1980s and early 1990s, driven by the need for smaller and more efficient electronic devices. Early SoCs were used in embedded systems and mobile phones, but as semiconductor technology advanced, SoCs became more powerful and versatile. Today, they are the backbone of modern consumer electronics, powering everything from smartphones and tablets to smartwatches, medical devices, smart TVs, automotive systems, and Internet of Things (IoT) devices. System-on-a-chips (
SoCs) are crucial in today's technology landscape because they enable high levels of integration and performance while minimizing power consumption and physical footprint. This is especially important in portable and wearable devices, where battery life and compact design are critical. Their integration also reduces the number of components on a circuit board, simplifying design, lowering manufacturing costs, and improving reliability.
Key features of SoCs include high integration, energy efficiency, real-time processing capabilities, and support for advanced connectivity. Their advantages are numerous, offering faster processing speeds, lower power consumption, reduced system size, and cost-effectiveness. Furthermore, many SoCs are designed with specific applications in mind, allowing for customization and optimization that further enhance performance and efficiency.
What is a PMIC?
A power management integrated circuit (PMIC) is a highly specialized semiconductor device designed to manage and regulate the power requirements of modern electronic systems. These circuits are essential in complex devices such as smartphones, tablets, laptops, wearables, and embedded systems, where multiple components require different voltage and current levels to operate efficiently and reliably. The PMIC acts as the central hub of power distribution, ensuring that each subsystem receives the correct amount of power at the right time, while also optimizing power usage to extend battery life and reduce heat generation.
PMICs typically integrate several key functions onto a single chip, including voltage regulation (using buck, boost, or low-dropout (LDO) regulators), battery charging and monitoring, power sequencing, thermal management, and fault protection. This level of integration not only saves circuit board space but also simplifies design and improves overall system reliability.
The concept of integrated power management began to gain traction in the late 1980s and early 1990s as the use of portable electronic devices, such as early mobile phones and laptops, became widespread. Initially, power management was handled by discrete components, which were bulky and less efficient. As semiconductor technology advanced, manufacturers began integrating these functions onto single chips, leading to the first generation of PMICs (Power-Integrated Microcontrollers). Over time, PMICs evolved to support increasingly sophisticated power architectures, such as dynamic voltage scaling and intelligent power management, which are now standard in energy-conscious designs.
Today, PMICs are a cornerstone of modern electronics, enabling devices to operate longer on smaller batteries, manage thermal loads more effectively, and meet stringent energy efficiency standards. They are especially important in battery-powered and space-constrained applications, where every milliwatt and every millimeter counts.
Figure 1. Traditional power management versus PMIC solution.
A discrete power management solution involves the use of individual components, such as separate buck converters, LDOs, battery chargers, and protection circuits, each performing a specific function. While this approach offers flexibility in selecting components tailored to exact specifications, it often results in a larger PCB footprint, greater design complexity, and more difficult management of thermal and electromagnetic interference (EMI). In contrast, a PMIC integrates multiple power functions onto a single chip, significantly reducing board space, simplifying the design process, and improving overall system efficiency. Figure 1 illustrates the contrast between traditional discrete power management and a PMIC-based solution, highlighting the advantages of integration. PMICs are particularly advantageous in space-constrained applications, such as wearable devices, where compactness, low power consumption, and optimized power sequencing are critical. Furthermore, PMICs typically include advanced features such as power monitoring, fault protection, and communication interfaces, which would require additional circuitry in a discrete configuration. Overall, while discrete solutions may be suitable for highly customized or high-power systems, PMICs offer a more efficient and reliable approach for modern, compact electronic designs.
Figure 2. Connection of the Analog Devices PMIC to a SoC.
A PMIC is typically connected to a SoC using a combination of power and communication interfaces to ensure efficient and coordinated power delivery. The PMIC supplies the various voltage rails required by the SoC, such as core voltage, I/O voltage, and memory voltage, using integrated regulators like buck converters and LDOs. These power rails connect directly to the corresponding power input pins on the SoC. In addition to power supply, the PMIC often communicates with the SoC via a digital interface such as I²C or SPI. This communication allows the SoC to control and monitor the PMIC's functions, including enabling or disabling power rails, adjusting output voltages, reading fault or status registers, and managing the power sequence during startup and shutdown. Figure 2 shows a typical connection diagram of a PMIC connected to an SoC, illustrating both the power and communication rails. This tight integration ensures that the SoC operates reliably and efficiently, especially in power-sensitive applications such as mobile and wearable devices.
Key Parameters to Consider When Powering a SoC with a PMIC
When integrating a PMIC to power a SoC, several critical parameters must be carefully evaluated to ensure reliable and efficient power operation. These parameters are typically derived from the SoC's datasheet or technical reference manual, which describes the chip's electrical and functional requirements. Understanding these parameters is essential for designing a robust power delivery architecture.
• Voltage Requirements: Understanding the power domains of the core, I/O, and peripherals.
• Current Demand: Estimating the maximum and average current draw for each rail.
• Power Sequencing: Determining the correct order of power-on and power-off events.
• Timing Constraints: Managing delays and ramp times between power rails.
• Power Modes and Transitions: Supporting dynamic power states for energy efficiency.
By the end of this guide, the designer will have a clear and practical framework for designing a power architecture that ensures reliable and efficient SoC operation. Whether you're new to SoC design or looking to refine an existing approach, this tutorial will give you the confidence to navigate the ignition path.
Typical Voltage Requirements:
Each SoC has multiple power domains, such as core logic, I/O interfaces, analog blocks, and memory, which often require different voltage levels. These voltages are usually specified in a datasheet in sections such as "Recommended Operating Conditions" or "Power Requirements."
• Core Voltage (VDDCORE): Powers the CPU and internal logic. This is often the lowest voltage (e.g., 0.8 V to 1.2 V).
• I/O Voltage (VDDIO): Powers the input/output interfaces. Common values are 1.8 V, 2.5 V, or 3.3 V.
• Analog Voltage (VDDA): Powers analog peripherals, such as ADCs or PLLs. It requires a stable, low-noise supply.
PMIC Selection Tips: Use LDOs or buck converters to efficiently generate these voltages.
Current Demand:
Each power rail must supply sufficient current to meet both average and peak demands. These values are typically found in the "Electrical Characteristics" section or estimated using power modeling tools provided by the SoC vendor.
• Peak current: Required during startup or in high-performance modes.
• Average current: Helps size power supplies and manage thermal design.
PMIC Peak Selection: Always add a safety margin (e.g., 20% to 30%) to your current estimates to account for transient loads and future scalability.
Power-up Sequence:
Many SoCs require the power rails to be powered on and off in a specific order to prevent lock-up, voltage dips, or damage. This sequence is usually documented in the "Power-up/Power-off Sequence" section of the datasheet.
• Typical order: Core voltage > Analog voltage > I/O voltage
• Dependencies: Some peripherals or memory interfaces may require synchronized power-up.
PMIC Tip Selection: Use PMICs with integrated sequencing or discrete power sequencers to automate this process.
Synchronization Constraints:
In addition to sequencing, the timing between lanes is important. This includes:
• Ramp time: how quickly a voltage reaches its target level.
• Delay time: the minimum waiting time between the activation of different lanes.
• Hold time: the time a lane must remain stable before the next stage begins.
PMIC Pin Selection: Check the timing diagrams in the datasheet and use programmable PMICs or microcontroller GPIOs to adjust the delays.
Power Modes and Transitions:
Modern SoCs support multiple power modes (e.g., active, idle, sleep, deep sleep) to optimize power efficiency. Each mode may require different voltage levels or enable/disable certain lanes.
• Dynamic Voltage Scaling (DVS): Adjusts the core voltage based on the workload.
• Power Control: Turns off unused blocks to save power.
PMIC Tip Selection: Choose PMICs that support dynamic control via I2C/SPI or GPIO to enable smooth transitions between power states.
Where are PMICs used and why are they important?
PMICs are found in most smartphones, tablets, and wearables. They are also found in laptops and ultrabooks, automotive electronics, IoT devices, and industrial and medical equipment.
For smartphone and tablet applications, the PMIC plays a critical role in ensuring efficient, safe, and intelligent power distribution throughout the device. These mobile devices are highly integrated systems with multiple subsystems, such as the CPU, GPU, memory, display, camera, wireless radios (Wi-Fi, Bluetooth, cellular), sensors, and storage, all of which have different power requirements. The PMIC manages these diverse needs in real time.
A Closer Look at the Role of PMICs in Modern Medical Equipment:
PMICs in medical equipment regulate multiple voltage rails, manage battery charging and backup systems, and ensure uninterrupted operation during power transitions or failures. For example, in portable or wearable medical devices, such as glucose meters or portable ECGs, the PMIC manages the power to rechargeable batteries, optimizes energy consumption to extend battery life, and ensures the device can operate safely even under low-power conditions. In
more complex systems, such as ultrasound machines, patient monitors, or MRI scanners, PMICs are integrated into the main control boards and supply precise voltages to the analog front-ends, digital processors, memory, and communication modules. These systems often require power sequencing, where different subsystems must be switched on or off in a specific order to prevent malfunctions or data loss. The PMIC manages this sequencing automatically, based on programmable logic or control signals from the system's microcontroller or processor.
Furthermore, PMICs used in medical applications typically include redundant safety features such as overvoltage protection (OVP), undervoltage lockout (UVLO), overcurrent protection (OCP), and thermal shutdown. These features are essential to prevent damage to sensitive electronic components and ensure patient safety. In implantable or wearable devices, PMICs are designed with ultra-low power consumption and may include energy harvesting interfaces to support wireless charging or power generated from body heat or movement.
Regarding integration, PMICs are typically mounted on the main printed circuit board of the medical device and are often selected or even custom-designed to meet specific power profiles and regulatory standards (such as IEC 60601) required in medical environments. Their compact size and high level of integration help reduce board footprint and improve system reliability—two crucial aspects in medical design.
Key Advantages of PMICs
• Efficiency: PMICs optimize power conversion and distribution, reducing energy loss and heat generation. This is especially important in battery-powered devices, where maximizing battery life is a top priority.
• Integration: By combining multiple power functions, such as voltage regulation, battery charging, and power sequencing, onto a single chip, PMICs reduce the need for discrete components. This saves board space, simplifies design, and lowers the overall system cost. • Reliability:
PMICs include built-in protection features, such as OVP, OCP, and thermal shutdown. These safety measures improve device durability and security, which is especially important in mission-critical applications, such as medical and automotive systems.
• Customization: Many PMICs are configurable or even custom-designed to meet a system's specific power requirements. This enables fine-tuned performance, improved thermal management, and seamless integration with the main processor or SoC.
Other PMIC Features:
Some PMICs are equipped with battery management, which handles charging, discharging, battery health monitoring, and protection. Very low power consumption during sleep mode and low-power modes help reduce energy consumption when the system is idle or in standby mode.
In the rapidly evolving world of wearable technology, energy efficiency, compact design, and feature integration are critical to delivering a seamless user experience. Analog Devices addresses these challenges with a wide range of highly integrated PMICs, each designed to meet the specific demands of wearable devices.
Whether developing a smartwatch, a health monitoring device, or a fitness tracker, these PMIC solutions achieve the perfect balance of integration, efficiency, and performance. These PMICs are designed to minimize board footprint, extend battery life, and simplify system design—key factors for the success of any wearable product. See Table 1.
Conclusion:
Powering a System-on-a-Chip (SoC) is much more than simply supplying voltage; it's a carefully orchestrated process that directly impacts system stability, performance, and efficiency. As SoCs continue to replace simpler microcontrollers in advanced applications, understanding their power requirements is becoming essential for all embedded system designers.
Starting with the SoC datasheet and focusing on five key conditions—voltage requirements, current demands, power sequencing, timing constraints, and power modes—you can build a power architecture that not only meets technical specifications but also supports long-term reliability and scalability. Integrating a Power-on-a-Chip Microcontroller (PMIC) into your design can simplify this process, offering features such as programmable sequencing, dynamic voltage scaling, and fault protection in a compact footprint.
Whether you're designing for wearables, industrial automation, or edge computing, mastering these power fundamentals will give you the confidence to tackle even the most complex SoC-based systems. So, enhance your design intelligently and let it shine.
About the author:
Hermogenes Escala is an Applications Engineer at Analog Devices, supporting the EMEA Central Applications Center (CAC). With a strong focus on switched-mode power supplies (SMPS) and power management, Hermo brings extensive hands-on experience and technical expertise to his role. He holds a Bachelor of Science in Electronic and Communications Engineering from Eastern Visayas State University (EVSU) and a postgraduate diploma in Power Electronics from Mapúa University, both in the Philippines.
Prior to joining ADI, Hermo held various design and support roles across multiple industries, including automotive dashboards, audio systems, power supply design for diverse applications, and medical devices. This experience has provided him with a broad and practical perspective on real-world engineering challenges. Passionate about innovation and continuous learning, he enjoys bridging the gap between complex technologies and practical applications.
