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 to go. This multi-function port can do just about anything – it can charge devices, transfer data, handle audio and video output, it even lets you plug in accessories.
How did we come here? Well, for years the European Union has been trying to get electronics manufacturers to agree on a common standard to avoid the mess (and waste) that proprietary connectors create. At first, microUSB was the connector of choice, but with the arrival of USB Type C, or USB-C for short, the industry has moved on to the new standard.
And thanks to a European regulation that will come into force at the end of 2024, USB-C is mandatory for practically all portable electronic devices (with some exceptions for smaller devices like smartwatches).
Most smartphone manufacturers have readily embraced USB-C, just as they did before microUSB. The only big hurdle is Apple, which still uses Lightning on its iPhones, AirPods and EarPods – that’s it, everything else has moved to USB-C, including the new Apple TV remote.
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 iPhone and computer or when moving RAW photos from memory card to iPad.
Did you know that there is actually a Lightning-based card reader that works at USB 3.0 speeds? Faster transfers are therefore possible, but apparently this is a difficult feat to achieve and only iPad Pros support it. And even then, Apple never released a video adapter that could exceed 1080p.
Lightning is also limited in the amount of power it can carry. The iPhone charger tops out at 30W, while Apple’s USB-C charger for the new MacBooks can put out 140W. Okay, that’s not quite standard, but that’s not even the maximum that USB-C can carry.
Let’s try to keep things organized and break down the major functions of USB-C one by one.
USB started life as a data port. USB 1.0 and 1.1 are slow dogs 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 detail). Right in the middle is a single D+/D- pair, this is your typical USB 2.0 cable’s data connection and is mandatory for USB-C. This ensures that all cables will have at least some connectivity.
The pinout of a USB Type C cable
USB 3 added extra cable pairs for data transfer – there are four extra pairs in a USB-C socket. While USB 2 is limited to 480MB/s, the extra wiring of a USB-C cable enables transfer speeds of 10, 20, 40, and even 80GB/s.
Small precision: the USB-C connection is used by USB, of course, but also by Thunderbolt. This distinction is set to disappear as USB 4 is based on Thunderbolt 3 and the newer USB 4 version 2 is based on Thunderbolt 4.
Another great application is PCI-Express signal transport – essentially a hard-wired version of the PCIe slots on a computer motherboard. This allowed external GPUs to be connected to laptops using a single cable.
Another popular use for USB-C is for video output. DisplayPort is probably the most common use and USB-C has mostly replaced the old big 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, possibly a card reader, audio and mic jacks, etc. Such hubs are built into some monitors, allowing you to start a full desktop experience by plugging in a single cable.
It’s pretty handy for laptops, sure, but several smartphone makers offer desktop modes – Samsung’s DeX, Motorola’s Ready For, Huawei has one too. Even Apple has one, Stage Manager for iPad Pros (which use USB-C, of course).
There are other options as DisplayPort, MHL and HDMI adapters are also available. Some of them are active adapters that convert from one standard to another, but there are also simple passive adapters.
We will briefly discuss audio here. The USB can power an external DAC that you can plug headphones into. However, as with video output, there is also a passive option – audio adapter accessory mode.
USB-C has a lot of pins to work with and some of them can be remapped to the wiring needed for a typical TRRS jack, so a simple passive adapter can connect headphones with a microphone. Note that this is a purely analog mode and the digital circuits are disconnected to avoid noise.
The basic USB standard has fairly low power limits (500mAh for USB 2.0), although most manufacturers don’t follow the standard to the letter, so 10W adapters are fairly common.
Of course, manufacturers want their products to stand out and fast charging is one way to achieve that, especially now that smartphone batteries range in size from 3-6000mAh. This has led to many proprietary solutions such as Qualcomm’s Quick Charge and Oppo’s VOOC.
The standard method, however, is USB Power Delivery (USB-PD for short). The initial version prescribed several voltages and current levels that could be supported – 2A at 5V, plus 3A or 5A at 12V or 20V. This gave Power Delivery a fairly wide range of 10W to 100W.
However, these fixed voltages require DC to DC conversion inside the phone to bring them back to something more suitable for the lithium battery inside. USB-PD revision 2 introduced a few extra voltages – 9V and 15V – but that wasn’t enough.
Revision 3 allows devices to talk to their chargers and request a specific voltage. It can range from as low as 3.3V to 21V and it can be fine tuned in 20mV steps. Chargers that support it are marked “Programmable Power”. That 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 mode||5V
|Prog 5V (3.3V to 5.9V)
Prog 9V (3.3V to 11.0V)
15V Prog (3.3V to 16.0V)
Prog 20V (3.3V to 21.0V)
|Current||Round (PDP/Voltage) to the nearest 10 mA||RoundDown (PDP/Prog Voltage) to nearest 50mA|
|step size||None||Nominal 20mV|
|Current limit mode||None||Yes, no 50 mA nominal|
|Periodic RDOs during operation||No – not applicable||Yes, necessary for the operation of the PPS|
|Requires robust port design||Yes||Yes|
The latest USB-PD Extended Power Range standard adds more fixed voltages – 28V, 36V and 48V. This made the new maximum power of 240W (48V at 5A), which is enough even for beefy laptops (although phones are already close to the 240W limit). There is also a new adjustable voltage supply option, which allows the device to gradually adjust the voltage between 15V and 48V in 100mV steps.
Note that for security reasons such powerful cables require a chip called “e-marker”. This chip signals to the charger and the phone (or laptop or whatever) that the cable is capable of carrying the extra power.
While we love USB-C, we can’t claim it’s perfect. Our only major complaint is that while it has so many capabilities, not all devices and cables support everything. Many of the features we mentioned above are optional.
What’s worse is that it can be very difficult to determine which devices and which cables support what. USB-IF tries to make things clearer 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 has become an absolute monster. Did you know there is no more USB 3.0? It used to be reliable USB 3.1 Gen 1. But that doesn’t exist anymore either, it’s USB 3.2 Gen 1 now.
Things got even clumsier with titles like USB 3.2 Gen 2×2. Ugh. Fortunately, all of that will be replaced by much clearer labels: USB 5 Gbps, USB 10 Gbps, USB 20 Gbps, and USB 40 Gbps (and, presumably, USB 80 Gbps soon). Much better.
As for the power, there will be two levels – USB 60W and USB 240W. There won’t be a 100W label because apparently the difference between the 100W cables and the 240W cables is small enough that by the time the new labels come into play it won’t have any more meaning to sell 100W cables.
USB-C has been great – we use it to charge our phones, laptops, headphones, razors, flashlights, and just about anything that has a battery inside and fits in a backpack.
This allowed us to create comfortable workplaces at our desks with monitors, keyboards, mice, etc. that come to life by plugging in a single cable. And given that the latest standards allow it to carry far more data and power than the original spec, USB-C is probably not done evolving yet.
Will there ever be a USB-D? Maybe, but not anytime soon. Will the world ditch the wires and go wireless? Probably not – it’s not an efficient way to recharge. It’s also not ideal for data, 2.4 GHz Wi-Fi is already painfully congested in apartment buildings and 5 GHz is also getting quite congested, which caused the Wi-Fi Alliance to pass to the 6 GHz band.
For the foreseeable future, USB-C is the one cable that rules them all.
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