Flashback: USB-C, the one cable to rule them all
The battle for the wired smartphone connector is over, and USB-C is the way forward. This multipurpose port can do almost anything – it can charge devices, transfer data, handle audio and video output, it even lets you connect accessories.
How did we get here? Well, for years now the EU has been trying to entice electronics manufacturers to settle on a common standard to avoid the mess (and waste) that proprietary connectors create. Early on, microUSB was the connector of choice, but with the arrival of USB Type C, or USB-C for short, the industry switched over to the new standard.
And thanks to some EU regulations coming into effect at the end of 2024, USB-C is mandatory for pretty much all portable electronics (with some exceptions for the smallest devices like smartwatches).
Most smartphone manufacturers readily adopted USB-C, just as they did microUSB before it. The one big holdout is Apple, which still uses Lightning on its iPhones, AirPods and EarPods – that’s it, everything else has moved on to USB-C, including the remote control for the new Apple TV.
We think Apple’s lineup is a good illustration of why USB-C is so good. Lighting is basically a USB 2.0 port. This means slow data transfers when syncing files between an iPhone and a computer, or when moving RAW images from a memory card to an iPad.
Did you know that there is actually a Lightning-based card reader that runs at USB 3.0 speeds? So faster transfers are possible, but apparently it’s a difficult feat to accomplish, and only iPad Pros support it. And even then, Apple never released a video adapter that can go above 1080p.
Lightning is also limited in how much power it can carry. The charger for iPhones tops out at just under 30W, while Apple’s USB-C charger for the new MacBooks can deliver 140W. Okay, it’s not quite standard, but it’s not even the maximum that USB-C can carry.
Let’s try to keep things organized and break down the most important features of USB-C one by one.
USB started life as a data port. USB 1.0 and 1.1 are dog-slow and barely remembered now, USB 2.0 is still very much alive. USB-C has a total of 24 pins, 12 on each side (well, 22 pins, but let’s not get bogged down in details). Right in the middle is a single D+/D pair, this is the data connection on your typical USB 2.0 cable and is mandatory for USB-C. This ensures that all cables have at least some connection.
Pin-out of a USB Type C cable
USB 3 added additional pairs of cables for data transfer – there are four extra pairs in a USB-C connector. While USB 2 is limited to 480 MBps, the additional cabling of a USB-C cable enables 10, 20, 40 and even 80 GBps transfer speeds.
A quick note: the USB-C connector is of course used by USB, but also by Thunderbolt. This distinction is set to disappear as USB 4 is based on Thunderbolt 3 and the new USB 4 version 2 is based on Thunderbolt 4.
Another interesting application is to carry PCI-Express signals – this is basically a wired version of the PCIe slots on a computer’s motherboard. This has made it possible to connect external GPUs to laptops using a single cable.
Another popular use of USB-C is video output. DisplayPort is probably the most common use, and USB-C has mostly replaced the old, large DP port. More importantly, it’s not data OR video, it’s data AND video AND power.
This allows a single device to connect to a hub that adds a standard HDMI port, multiple USB Type A and Type C ports, perhaps a card reader, audio and microphone jacks, etc. Such hubs are built into some monitors, so you can boot up to a full desktop experience by connecting a single cable.
It’s pretty handy for laptops, of course, but several smartphone manufacturers offer desktop modes – Samsung’s DeX, Motorola’s Ready For, Huawei has one too. Even Apple has one, Stage Manager for iPad Pros (which of course uses USB-C).
There are other options besides DisplayPort, MHL and HDMI adapters are also available. Some of these are active adapters that convert from one standard to another, but there are also simple passive adapters.
We’ll quickly mention sound here. USB can power an external DAC to which you can connect headphones. However, as with video, there is also a passive option – Audio Adapter Accessory mode.
USB-C has plenty of pins to work with, and a few of them can be reattached to the cables needed for a typical TRRS connector, so a simple passive adapter can connect a headset with a microphone. Note that this is purely analog mode and digital circuits are disconnected to avoid noise.
The basic USB standard has fairly low current limits (500mAh for USB 2.0), although most manufacturers do not follow the standard to the letter, so 10W adapters are quite common.
Manufacturers naturally want their products to stand out, and fast charging is one way to do that, especially now that smartphone batteries are more 3-6,000 mAh in capacity. This led to many proprietary solutions such as Qualcomm’s Quick Charge and Oppo’s VOOC.
However, the standard method is USB Power Delivery (USB-PD for short). The original version specified multiple voltages and current levels that could be supported – 2A at 5V, plus 3A or 5A at either 12V or 20V. This gave Power Delivery quite a wide range from 10W to 100W.
However, these fixed voltages require DC to DC conversion inside the phone to bring them down to something more suitable for the lithium battery inside. USB-PD Revision 2 introduced a few more voltages – 9V and 15V – but it wasn’t enough.
Revision 3 allows devices to talk to their chargers and request a specific voltage. It can vary from as little as 3.3V to as high as 21V, and it can be set precisely in 20mV steps. Chargers that support this are labeled “Programmable Power Supply”. This way, the charger is the one handling the extra heat, not the phone (lithium batteries don’t like it when things get hot).
|Aspect||Fixed source||Programmable power source|
|Constant voltage state||5V
|5V Prog (3.3V to 5.9V)
9V Prog (3.3V to 11.0V)
15V Prog (3.3V to 16.0V)
20V Prog (3.3V to 21.0V)
|Present||Round (PDP/voltage) to the nearest 10mA||RoundDown (PDP/Prog Voltage) to the nearest 50mA|
|Step size||None||Nominal 20 mV|
|Current limit state||None||Yes, nominal 50 mA steps|
|Periodic RDOs in operation||No – does not apply||Yes, required for PPS operation|
|Requires robust gate design||Yes||Yes|
The latest USB-PD Extended Power Range standard adds more fixed voltages – 28V, 36V and 48V. This gave the new maximum 240W current (48V at 5A), which is enough for even powerful laptops (although phones are already close to the 240W limit). There is also a new adjustable voltage supply setting which allows the device to gradually adjust the voltage between 15V and 48V in 100mV increments.
Note that such heavy-duty cables require a chip called an “e-marker” for security reasons. This chip signals to the charger and phone (or laptop or whatever) that the cable is capable of carrying the extra current.
As much as we like USB-C, we can’t pretend it’s perfect. Our one biggest complaint is that while it has so many options, not all devices and not all cables support everything. Many of the features we mentioned above are optional.
The worst thing about it is that it can be very difficult to figure out which devices and which cables support what. USB-IF is trying to fix things with new labels that clearly indicate how much data and power a given cable can carry.
This should also solve our other complaint, the naming scheme grew to be an absolute monster. Did you know that there is no longer USB 3.0? It was relabeled USB 3.1 Gen 1. But that doesn’t exist anymore either, it’s USB 3.2 Gen 1 now.
Things got even more awkward with titles like USB 3.2 Gen 2×2. Oh. Fortunately, all that will be replaced with the much clearer labels: USB 5Gbps, USB 10Gbps, USB 20Gbps and USB 40Gbps (and presumably USB 80Gbps soon). Much better.
As for power, there will be two tiers – USB 60W and USB 240W. There won’t be a 100W label as apparently the difference between 100W cables and 240W cables is small enough that when the new labels come into play it won’t make sense to sell 100W cables anymore.
USB-C has been great – we use it to charge our phones, laptops, headphones, shavers, flashlights and just about anything else that has a battery inside and fits in a backpack.
It has allowed us to create comfortable workplaces at our desks with monitors, keyboards, mice and so on that all come to life by connecting a single cable. And given that the latest standards allow it to carry many times more data and power than the original specification, USB-C probably isn’t done evolving yet.
Will there ever be a USB-D? Possibly, but not immediately. Will the world ditch cables and go wireless? Probably not – it’s not an efficient way to charge. It’s not great for data either, 2.4GHz Wi-Fi is already painfully congested in apartment buildings, and 5GHz is also getting pretty crowded, which has pushed the Wi-Fi Alliance to move into the 6GHz band.
For the foreseeable future, USB-C is the one cable to rule them all.