Teardown: Pixel Stand provides (some) Google fans with faster wireless charging than Qi-EDN

2021-11-10 03:45:59 By : Ms. Sofia Wu

In my article on the status update of wireless charging in late March 2019, which was published shortly after the single-coil Q1 charger was disassembled and before the subsequent dissection of the dual-coil unit, I wrote:

Google added native (rather than clumsy accessory additions) wireless charging to the Pixel 3 smartphone series at the end of 2018. The last one is the source of the "trap" qualifier...Unlicensed third-party chargers are limited to 5W functions. Even now, six months later, your only option to charge Pixel 3s at 10W is Google’s own $79 Pixel Stand (due to concerns about compatibility? Profitability? Both? You decide.).

Since then, I have been eager to get into it and try to figure out how it differentiates. In retrospect, my sole source statement was not entirely accurate, although in fact I was still accurate. As pointed out in the 9 to 5 Google article I linked to, Belkin also announced the base and bracket variants of the "Boost Up" charger, which provides 10W charging for Pixel phones (and 5W support for standard phones):

They are no longer available (I am linking to the Amazon product page here because the corresponding page on the Belkin website no longer exists) and my feeling is that they have never been shipped in large quantities. Ironically, the first-generation Pixel Stand product page no longer exists on the Google website; it will automatically forward to the newly released (but not yet shipped as of this writing) second-generation Pixel Stand page, which Provide the latest Pixel 6 series phones with a charging capacity of up to 23W, and up to -15W to support other phones that support EPP:

This is the Amazon page of the first generation Pixel Stand as an alternative source of information.

Speaking of compatibility, what are the "(some)" qualifiers in the title of this article? The first generation Pixel Stand was launched together with Pixel 3 and the larger Pixel 3 XL. This is the first Google phone that supports wireless charging (the link points to iFixit’s disassembly of these two phones, so you can see the charger’s Circuit inductive matching). In other words, it also supports the subsequent Pixel 4 and Pixel 5 at a charging speed higher than 5W. However, it does not support the "A" Pixel variants, which are often the main phones I use, and (among other things) the wireless charging support is omitted in order to save costs.

Enough overview; let's start the teardown! I will start with some overview photos as usual (I bought this special device from eBay; the stand itself is not used, but the original owner kept the 1.5m USB-C cable and 18W USB PD power adapter for wired charging telephone):

Pay attention to the plastic protective film on the charging board (remove before use). Below is a separate photo of the bracket (with the plastic film removed) and a cent coin (pixel bracket, usually 0.75 inches (19.1 mm) in diameter) for size comparison purposes. According to the Amazon product page, it measures 4.1 x 3.6 x 4.1 inches and weighs 5.6 oz):

Now one of my Pixel 3a phones (it doesn’t support wireless charging...you guys think about this concept):

Take off the phone, turn the Pixel Stand upside down, and... more protective plastic!

Remove it to clearly see the USB-C port:

By the way, the FCC ID: 2APYSG019C is also printed on the bottom (among other things). In terms of its value, the certification document identifies the device as "Lanto Electronic Ltd Wireless Charger".

It's time to dive in, starting from the bottom, it turned out to be easier to remove than I feared. Unlike this Neanderthal, I chose a civilized small flat-head screwdriver instead of a hunting knife:

Untie a few labels, tear off some glue, and then:

Not much to see, although those two Faraday cages (or radiators? or both?) are interesting:

At this point, I turned my attention to the charging pad, which is easy to separate again...at least at a certain point:

It stubbornly refused to leave the base completely; until I re-examined the base, removed two screws from the center and cut some wires:

The inside of the front cover (bottom) has nothing to write, but the second half (top) is more interesting. It is conceptually reminiscent of the dual-coil layout of the Seneo unit. Its disassembly EDN was released in December 2019, including the "portrait" (top) and "horizontal" (bottom) coil directions (when placed in two possible locations). Optimized the orientation of the device when the device is facing) Stand; by the way, have you also noticed the beautiful ridges built into the charger to prevent the device from slipping? ). But it adds a square sensor (or something) in the middle of each coil:

I guess they are used for temperature monitoring purposes to prevent overheating. reader?

The back of the metal plate (as opposed to the fragile plastic with Seneo) that holds the two coil assemblies together is stubbornly taped to the plastic half-chassis behind it:

With this, let us turn our attention to the PCB on the base. The initial disassembly steps are very simple, when I removed four more screws and peeled the metal plate from the plastic top chassis part:

At this point, I was initially stumped; the two metal "lobes" (because there is no better word) were firmly attached to the PCB and resisted all initial attempts to pry them off with a flat-head screwdriver. So I temporarily turned my attention to the connection between the PCB and the metal plate behind it, which is more suitable for my deception:

This is a close-up of a translucent lens that focuses and redirects the output of the LED located on the PCB to the outside world:

Speaking of which... back to the front of the PCB. Have you noticed seven holes: four in one "leaf" and three in "another"?

Well, I tried to snap a tip of the precision tweezers into one of them and use it to lift the "flap", which only caused me to bend the tip of the tweezers. The heat gun did not work either, although through its application I learned that the back of the PCB includes several sticky protective tapes:

However, I am happy to report that one final application of a flat-head screwdriver, with more muscles (and colorful accompanying language) and using the USB-C connector as a fulcrum, has finally achieved success:

Look. First, please pay attention to the above-mentioned LEDs on the bottom of the PCB.

In the lower left quadrant of the photo are two horizontally dominant ICs: an IDT (now Renesas Electronics) P9242-R wireless power transmitter "for 15W applications" (I quoted the data sheet) and a Winbond 25X40CLNIG 4 Mbit serial flash memory . There are two devices with the same label in the upper right quadrant:

This disassembly tells me that they are AOS AON6996 dual N-channel MOSFET devices. There are two more on the other side of the PCB:

Along with them is a mysterious (at least to me) STMicroelectronics STM32 microcontroller (you may remember that I could not clearly identify STMicroelectronics µC in the Seneo teardown). Say it again... readers?

Admittedly, I am still a bit frustrated when I quit this project, because I can't figure out exactly how Pixel Stand knows that it has a Pixel phone (compared to traditional Qi-supported devices) and therefore improved its charging ability. In this small Reddit disassembly and discussion topic, there is an article that assumes that "the ability to draw 10W is triggered by the data stream embedded in the Qi transmission."

I am not aware of any specific wireless handshake that occurs between the wireless transmitter and receiver, but I also admit that I am not very familiar with the Qi specification. What I can determine from the Qi entry on Wikipedia is:

The regulation of the output voltage is provided by a digital control loop, where the power receiver communicates with the power transmitter and requests more or less power. The communication from the power receiver to the power transmitter by backscatter modulation is unidirectional. In backscatter modulation, the power receiver coil is loaded, changing the current consumption of the power transmitter. These current changes are monitored and demodulated into the information required for the two devices to work together.

As always, we welcome feedback from knowledgeable readers on this or any other content I have introduced (or ignored)!

— Brian Dipert is the editor-in-chief of Edge AI and Vision Alliance, a senior analyst at BDTI, and the editor-in-chief of the company's online newsletter InsideDSP.

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