Samsung’s Upcoming PMIC, S2MIW06, Is Redefining the Future of Wireless Charging

Why do we need wireless charging?

Most of us are familiar with the hassles that come with using a charging cable: It can get tangled or yanked out, it’s hard to plug in when it’s dark, and you can easily damage the charging port or the connector — especially if there’s water involved. Then there’s also the issue of charger compatibility, which can lead to having a large collection of charging cables that go mostly unused. Reducing these inconveniences and inefficiencies are the driving factors behind wireless charging, since all you need to do is place your device on a wireless charging pad.

Wireless charging has become ubiquitous, but you might be hard pressed to explain how it transmits electric current without a cable. Well, it’s actually pretty simple. Most wireless chargers use electromagnetic induction. Basically, an alternating current flows through the charging pad’s transmitter coil and creates a magnetic field. Then, when that field enters your smartphone’s receiver coil, electric current is generated¹ and it flows into your smartphone’s battery.

Of course, every technology has its own advantages and challenges, which result in focus points for both the industry and typical users. In the case of wireless charging, these are compatibility, speed (high power), safety, and reliability. Let’s dive into how all of this works.

How do we keep wireless charging compatible?

There are globally recognized certification standards that facilitate better charging, improved safety and increased compatibility between devices and brands. Qi (pronounced “chee”) is one of the best-known standards for wireless power charging, and it is developed by the Wireless Power Consortium (WPC), which includes over 300 major manufacturers.²  The latest version is Qi v2.2, and Samsung System LSI is actively participating in its implementation.³

The Qi standard considers many different factors to ensure better wireless charging experiences, including compatibility & certification between transmitters and receivers, compliance of charging power with the Qi protocol, and debris-detection algorithms for safety. The standard is further divided into three power profiles, which will be explained below.

1. Baseline Power Profile (BPP)
BPP is the most basic profile and was first introduced with Qi v1.0 in 2010, allowing wireless charging transmitters and receivers to provide up to 5W of electric power. The receiver (Rx) supports basic one-way communication that tells the transmitter (Tx) the amount of power it is currently receiving via ASK,⁴ enabling the Tx to control the power.

2. Extended Power Profile (EPP)
EPP raises the maximum charging power to 15W, with the Tx and Rx using two-way communication to choose either fast charging or normal charging. The Rx notifies the Tx that it is capable of high-speed charging,⁵ and the Tx notifies the Rx that it has the same capability.⁶ EPP also adopts an appropriate hardware structure to enable higher-power charging, a fast-charging protocol, and a more precise debris detection algorithm.

3. Magnetic Power Profile (MPP)
MPP offers similar advantages to EPP with magnetic attachment for enhanced usability. The magnetic alignment allows users to reliably use their smartphone during wireless charging and reduces issues that may occur when the Tx and Rx are not aligned, such as low power charging or no charging taking place at all. The charging frequency band was also changed to 360kHz in order to avoid clashes between mobile devices and remote car keys that use similar BPP/EPP frequencies. Many smartphone makers are expanding the wireless charging capacity of their products to 25W, and MPP supports stable 25W charging.

The sophisticated engineering behind wireless charging

When we use wireless charging in everyday life, it just works — so well that we might even take it for granted. But there is also amazing electrical engineering at the foundation of this technology, an example of which is shown in the figure above. It’s the structure of a wireless charging system being developed by System LSI, which includes S2MIW06, a wireless charging PMIC that provides system control through wireless power transfer and in-band communication.

The system achieves wireless power transfer through the following steps: First, the DC power input gets converted into AC power through the Tx inverter, before the AC power gets amplified by the Tx LC tank,⁷ indexed to inductive wireless-charging frequency characteristics. At that point, the AC power sent to the Rx's LC tank is rectified to DC voltage (VRECT) by the PMIC's rectifier. Once the power has been rectified into DC VRECT, the Rx PMIC converts it into a cleaner DC power output voltage (V_out) via a low-dropout (LDO) regulator before finally delivering it as power for charging the Rx battery. S2MIW06 sets itself apart by featuring a hardware design optimized for wireless power transfer, with a high power-transfer efficiency of up to 98%⁸, based on the Rx IC.

Of course, the transmission of wireless charging power is crucial during wireless charging. But communication between Tx and Rx is critical, as well. In some cases, the power sent by the Tx could be deficient or excessive, leading to overheating. When this happens, the Rx must notify the Tx to adjust the level of the power transmitted. Additionally, fast charging can only be carried out on Tx wireless charging pads that have been verified as safe through authentication between Tx and Rx. Wireless charging IC communication is responsible for these features.
 

How is S2MIW06 pioneering the field of wireless charging?

But what is the current wireless charging landscape, and where does Samsung System LSI fit into the equation? In fact, we play a key role when it comes to technical leadership as well as innovation that creates new ways forward for the industry. For example, one of the most important criteria of wireless charging user satisfaction is powerful firmware-based micro controller unit (MCU) operation that supports compatibility. S2MIW06 supports all BPP/EPP/MPP standards and has been tested to ensure compatibility with certified Tx pads, as well as hundreds of other Tx pads that have not been certified through internal testing. Therefore, S2MIW06 supports consistent performance under a wide variety of situations, as well as the flexibility of MCU operations based on market-leading, large-capacity built-in memory.
 

Apart from powerful firmware-based operations, charging power is also an important factor when it comes to Rx ICs. S2MIW06 has this covered, though, supporting high-power wireless charging up to 50W so that it’s sufficiently future-proofed. The graph below shows S2MIW06’s Rx IC figure of merit (FOM) in terms of charging power and internal memory capacity, which is much better than the other Rx ICs, labeled A-D in the figure. It’s also worth mentioning that S2MIW06 has properly completed pre-testing for Qi certification through our PMIC knowledge that has been accumulated over the years.

S2MIW06 also operates in Tx mode to support the wireless battery sharing function available on smartphones. When it is working in this mode, the external filter for ASK demodulation takes up a significant amount of the printed circuit board (PCB) surface. To address this potential challenge, S2MIW06 is equipped with an innovative feature, based on advanced technology, which enables built-in filters to decrease external PCB surface by approximately 15% compared to when the filters are not built in.⁹

But how reliable is the communication that takes place between the wireless charging PMIC S2MIW06 and the device it is charging? As it turns out, quite reliable. S2MIW06 relies on in-band communication that sends the signal along with the AC power band being transmitted. This eliminates the cost of additional communication chips, and the robust hardware design ensures reliable communication over the entire power range of commercial wireless charging.
 

What’s next for wireless charging?

Few could have previously imagined wireless charging becoming a reality, but now that it has, it is an essential technology that has extended its range of applications to everyday items such as automobiles and even furniture like sofas and beds. At this point, the aim is to standardize the technology in terms of Qi to allow for convenient charging regardless of location. In fact, most smartphone manufacturers are already developing their products according to standardized requirements. With this being the case, Samsung will use its refined technical knowledge to lead the way in providing you with the latest seamless and efficient charging technology.

We have an established record of mass producing and applying wireless charging ICs to premium smartphones and wearables. Not only that, but we always seek to lead the way in implementing the newest technological standards to our products so you can safely and efficiently enjoy the stable performance of standardized wireless charging technologies as quickly as possible. And by creating an environment that has over 300 charging pads available for charging and discharging experiments, we have built an extraordinary system for physical verification that clearly demonstrates our industry leadership. With this strong foundation, Samsung is well positioned to provide the best products currently available while simultaneously forging a path forward to new possibilities.

* All images shown are provided for illustrative purposes only and may not be an exact representation of the product or images captured with the product. All images are digitally edited, modified, or enhanced.

_{¹⁾ The alternating current is induced according to the law of electromagnetic induction.
²⁾ According to the WPC’s website wirelesspowerconsortium.com, which states that the consortium is made up of large household brands as well as smaller and start-up technology companies, all of whom recognize the need and benefits of standards.
³⁾ System LSI joined the WPC in January 2023 and has been involved in implementing Qi.
⁴⁾ Amplitude Shift Keying (ASK) is a modulation technique used in digital data communications, and it is widely adopted in various systems including wireless charging systems. The Rx sends information back to the Tx by modulating the load on the power transfer system.
⁵⁾ Via “Rx to Tx ASK” communication.
⁶⁾ Via “Tx to Rx FSK” communication. Frequency-shift keying (FSK) is another widely-adopted modulation technique used in digital data communications. The Tx sends information back to the Rx by shifting the frequency of a carrier signal.
⁷⁾ An LC tank is an electric circuit consisting of an inductor connected with a capacitor. The circuit can act as an electrical resonator, an electrical analogue of a tuning fork, storing energy that oscillates at the circuit’s resonant frequency. LC circuits are used either for generating signals at a particular frequency from a more complex signal.
⁸⁾ All product specifications reflect internal test results and are subject to variations by user’s system configuration. Actual performance may vary depending on use conditions and environment.
⁹⁾ All product specifications reflect internal test results and are subject to variations by user’s system configuration. Actual performance may vary depending on use conditions and environment.}