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Introduction

Power management integrated circuits (PMICs) are essential in today's electronic devices. They manage power delivery and consumption, provide efficient power supplies, and drive power switches that control actuators and motors, as illustrated in Fig. 1.1. PMICs can be integrated into complex integrated circuits (ICs) or implemented as dedicated ICs. In this book, the term PMIC will refer to any type of power integrated circuit.

The importance of PMICs has grown significantly in recent years, driving innovation and progress in various industries, from consumer electronics to automotive and industrial applications. With the progress of machine learning and artificial intelligence (AI), intelligent power management is critical to supplying complex processors and sensors.

PMICs have enabled the development of smaller, more energy-efficient, and reliable electronic solutions. They also play an essential role in environmental aspects and sustainability. By regulating the power supply of electronic devices, PMICs can reduce energy consumption and carbon emissions. Moreover, PMICs are crucial for the development of renewable energies, such as solar and wind power, by enabling efficient power conversion and management.

1.1 What Is a Power Management IC and What Are the Key Requirements?

A PMIC is an electronic component that delivers one or more supply voltages to other circuit blocks at a sufficient power level out of an electrical energy source, as shown in Fig. 1.1. The power conversion can happen in a linear way (usually the more straightforward method) or a switched-mode fashion, delivering energy portions at a specific frequency (usually the more energy-efficient approach).

The PMIC aims to utilize the energy source at maximum efficiency, while the input and output voltage may vary during operation. It also reacts to varying load currents from a few microamperes (standby) to several amperes (full-power operation).

The voltage conversion ratio is the relation between the output and input voltage. The input voltage can be greater or lower than the output voltage , defining a step-down converter (buck converter) or a step-up converter (boost converter). Buck-boost converters allow to vary over a wide range below and above .

Figure 1.1   The role of power management: placed between the energy source and the electronics, it provides one or multiple supply voltages at the correct power level required by the application.

Source: Brunbjorn/Adobe Stock; daniiD/Adobe Stock; Ruslan Kudrin/Adobe Stock; estionx/Adobe Stock.

The power conversion efficiency (sometimes also called ) is defined as the ratio between the output power delivered to the load and the input power dissipated from the energy source,

where accounts for the power dissipated within the power management circuit. It needs to be delivered from the input but does not contribute to the output power. We want to keep as low as possible. For , the efficiency reaches its maximum, . It is common to express the efficiency in percent. In that case, we multiply Eqn. (1.1) by 100%.

PMICs typically include various features like voltage regulators, battery chargers, and power management control algorithms. They may also include monitoring and protection against overcurrent, overheating, and other failure cases. In some applications such as automotive, PMICs are alternatively called smart power ICs, emphasizing the combination of power devices with smart control and monitoring features, all integrated on a single chip.

One major trend is the increasing integration of PMICs. As more functions are combined onto a single chip, the resulting system becomes smaller, more efficient, reliable, and less expensive.

To summarize, the key requirements of PMICs are

• Size, volume, footprint, and weight: The PMIC, including external passive components, must often fit into a confined space like in smartphones or wearables. In portable devices, also the weight is critical. The lower weight is also crucial in automotive as it reduces gas and energy consumption.
• Power conversion efficiency: High efficiency means low losses. The lower the power losses, the longer the battery time. It also causes reduced heat and lower cooling effort, which, in turn, reduces the size and weight of the power management solution.
• Reliability, no disturbances, and low noise: PMICs are noise sources that may impact other sensitive electronic parts due to their switching nature. Handling high voltages and currents causes stress and reliability issues at the component, package, and assembly levels.
• Cost: Like most microelectronic products, there is always some pressure to reduce the cost of the IC and the overall bill of materials at the system level. Power management is not always considered a key differentiator. At the same time, physics cannot be cheated, and PMICs are a fastly growing market with good margins.

1.2 The Smartphone as a Typical Example

Looking at Fig. 1.2a), it is impressive to see how far mobile phones have come since the early 1990s. Back then, phones could only make voice calls and had a standby time of about a day or less. The picture is not to scale, but it was bulky and about 500 g in weight. It is incredible to think about all the features and functions that modern smartphones have today, illustrated in Fig. 1.2b). It is a remarkable example of the outstanding advancements in modern microelectronics. Today's smartphones are much smaller, lighter (typically 150 g), and more powerful. They have considerable computing power, 4K video capture, high-end gaming, virtual reality functions, and higher display resolution. This achievement in performance is thanks to ultra-low-power microelectronics and dedicated power management. Additionally, it is noteworthy that making a phone call is no longer the primary use case for these advanced devices.

Now we do what we usually do not want to; we drop our precious smartphone and look at the electronics inside. Figure 1.2c) shows a printed circuit board of the iPhone 13. The entire electronics is implemented on a layered motherboard sandwich of which Fig. 1.2c) shows a major part. The white frame boxes indicate some of the many PMICs inside the phone. There are more PMICs on the reverse side and other printed circuit board (PCB) parts, including ICs for the audio amplifier and wireless charging. PMICs are a considerable part of the smartphone. Connected to the Li-ion battery with a typical cell voltage of 3.7 V, multi-phase DC-DC converters supply the application processor that comprises multicore CPU and GPU blocks. The voltage levels are dynamically scaled in the range of typically 0.25-1.5 V at load currents of more than 10 A (see dynamic voltage and frequency scaling in Section 1.7). The typical power consumption is in the range of a few watts. In comparison, desktop PC processors dissipate more than 100 W. Running at high switching frequencies of tens of MHz, the voltage converters achieve small size, ultralow profile, and near-load integration at high conversion efficiency. No active cooling is required.

Looking closely, we identify hundreds of tiny passive components surrounding the ICs, mainly capacitors and inductors. As they are energy-storing components, their size can be reduced by decreasing the storing times, in other words, by increasing the switching frequency of the power conversion. It defines one of the leading research goals of today's power management solutions - achieving faster switching while keeping the conversion efficiency high. We will continuously address this topic throughout this book.

Figure 1.2   a) The mobile phone in the early 1990s, b) the smartphone today, and c) the electronics of the iPhone 13 with PMICs marked by white boxes.

Source: a,b) aquatarkus/Adobe Stock; c) ifixit.

1.3 Fundamental Concepts

There are different ways to implement DC-DC converters that convert an input DC voltage to another voltage level. To keep it more practical, we consider a scenario of how to convert 12 to 2 V.

1.3.1 Using a Resistor - The Linear Regulator

We can use a simple resistor to convert 12 to 2 V, as shown in Fig. 1.3. For a load current of 1 A, a resistor of 10 results in . In reality, the resistor is replaced by a controlled transistor such that its conductance is adjusted depending on the operating conditions like input voltage and load current. This approach works very well. However, the voltage drop between input and output is converted into heat. That is why there is significant power dissipation in the resistor, in this example. The power loss is even larger than the output power . In terms of energy efficiency, this concept has a significant drawback.

Nevertheless, it is the fundamental principle of a linear voltage regulator and, by far, the most used power management circuit today. On the positive side, besides its simplicity, it gives a "clean" output voltage with a fast transient response.

Without the excessive losses, there would be no need for alternative power conversion concepts, as discussed in Sections 1.3.2-1.3.4 below. The lower the voltage drop across the resistor (the controlled transistor), the lower the power loss. For this reason, linear regulators are often called...