ST Speeds to a More Wireless World with 70W Fast Wireless Charging Chipset

October 09, 2021 by Kristijan Nelkovski

In a world demanding fewer wires, ST’s new wireless power receiver chip promises to deliver fast and efficient wireless charging to mobile and wearable devices.

The concept of wireless power transfer dates back to the late 1800s with the invention of wireless data transfer in telecommunications. However, only in the past decade has it found a proper use in charging the increasing amount of gadgets and devices that have started being used as a part of everyday life. 


A high-level timeline of wireless power transfer.

A high-level timeline of wireless power transfer. Image used courtesy of IEEE and Mi et al


Today's wireless chargers can bring power to anything from earbuds and phones to electric cars and even busses. They do this via electromagnetic induction, which allows for power transfer between two nearby coils, one situated inside a base station and one embedded into the device being charged.

For devices with a smaller footprint, these coils and their wires have to be smaller and thinner and thus work between shorter distances, usually less than a quarter of an inch. 

By using bigger coils in some applications, designers can create a wireless power transfer system that could work at distances of a couple of feet. The nature of electromagnetism also allows for this transfer through certain materials, which is why wireless base stations can be embedded into desks for phones or streets for vehicles.

As the world pushed for technology to become even more wireless, companies like STMicroelectronics (ST) focus on wireless charging and power transfer to ease electronic designs.

This article will look into a recent release from ST; however, before diving into it, it's essential to look into the design considerations at play in creating a wireless power system.


Wireless Power System Design

When designing wireless power transfer systems, multiple factors have to be taken into consideration. These variables range from the device's application to its form factor and even the materials that it's made out of. 

With this in mind, engineers have a few technology standards for developing these systems while picking the right materials and designing the adequate transmitter and receiver coils for optimal efficiency.

One of the greatest challenges when building a wireless charge system is charging time. This factor is largely due to the generally low efficiency between the sender coil's power input and the receiver coil's power output during wireless power transfer. 

Hoping to solve this challenge, ST has released a new chip for faster wireless charging.


Ditching the Wires: ST's Wireless Chipset

STMicroelectronics claims to have overcome this challenge by introducing its latest power receiver chip offering to bring wireless charge times closer to its wired predecessor. 


ST's latest wireless-power chipset: STWLC98.

ST's latest wireless-power chipset: STWLC98. Image used courtesy of STMicroelectronics


The chip in question is called the STWLC98 integrated wireless power receiver and is intended for use with mobile devices such as phones and wearables. 

According to ST, this chip can deliver up to 70W of power, and when implemented into a modern smartphone design, it can fully charge the device in just under 30 minutes. This chip is also fully compliant with the Qi EPP 1.3 industry standard for wireless charging used by many smartphone manufacturers, making it easy for implementation into current designs. 


An application block diagram for the STWLC98. Image used courtesy of STMicroelectronics [downloadable product brief]


The chip itself comes with a 32 bit, 64 Mhz ARM Cortex M3 core with 16 KB FTP, 16 KB RAM, and 80 KB ROM. It also features built-in over-voltage, over-current, and thermal protection, as well as built-in power management, which can enable energy saving and ultra-low power stand-by modes for increased efficiency.

The STWLC98 is designed to work in conjunction with ST's STWBC2-HP, a wireless power transmitter chip used to develop Qi-certified wireless power applications. The STWBC2-HP contains an embedded ARM 32 bit 64 MHz Cortex M0+ microcontroller or, more specifically, an STM32G071 microcontroller. 

These two chips can also work with the STSAFE-A110 secure element chip, storing Qi certificates and providing encrypted authentication.

Though this new release seems to pack a punch when it comes to wireless charging, let's take a look at the benefits of moving towards wireless charging as a whole.


Moving Towards a Wireless World

ST's wireless innovation has the potential to be used in multiple different existing applications while also opening the door for innovation and new alternative uses. Additionally, it could allow for revisiting some old applications where long charge times aren't suitable for practical use. 
Some examples of this would be electric bikes and scooters, drones, portable power tools, laptops, and Bluetooth speakers where a long charge time would be inconvenient and not functional.

Of course, smartphones and wearables have the most to gain by using this specific chip. However, investing and designing new wireless power transfer technology, in general, could benefit other areas like medical devices, both wearable and embedded. These devices would gain a lot with quick wireless charging since using wires and ports that can easily be damaged or broken might be a problem for patients with certain conditions. 

Ultimately, as manufacturers have adopted these types of technologies before, the STWLC98 chip (and other similar chips and variants), if it can deliver everything that it promises, could become the norm for future wireless devices.