Flashback: USB-C, the one cable that rules them all

The battle of the smartphone’s wired connector is over and USB-C is the way forward. This multifunctional port can do just about everything – it can charge devices, transfer data, handle audio and video output, and even let you connect accessories.

How did we get here? Well, the European Union has been trying for years to get electronics manufacturers to settle on a common standard to avoid the mess (and waste) that proprietary connectors create. Early on microUSB was the preferred connector, but with the arrival of USB Type C or USB-C for short, the industry turned to the new standard.

And thanks to some EU regulations that come into force at the end of 2024, USB-C is essentially mandatory for all portable electronic devices (with some exceptions for smaller devices like smartwatches).

Flashback: USB-C, the one cable that rules them all

Most smartphone makers have readily adopted USB-C, just as they did microUSB before it. The only big blocker is Apple, which still uses Lightning on its iPhones, AirPods, and EarPods — that’s it, everything else has moved to USB-C, including the remote for the new Apple TV.

We think Apple’s lineup is a good illustration of why USB-C is so good. The lighting is primarily a USB 2.0 port. This means slow data transfer when syncing files between an iPhone and a computer, or when transferring RAW photos from a memory card to an iPad.

Did you know there is already a Lightning-based card reader that works at USB 3.0 speeds? So faster transfers are possible, but it seems like a tricky feat and only the iPad Pro supports it. Even then, Apple has never released a video adapter that can go beyond 1080p.

Lightning is also limited in the amount of force it can carry. The charger for iPhones tops out at 30 watts, while the Apple USB-C charger for newer MacBooks can output 140 watts. Well, it’s not quite standard, but it’s not the maximum that USB-C can hold.

Let’s try to keep things organized and break down the main functions of USB-C one by one.

data

USB started life as a data port. USB 1.0 and 1.1 are slow and barely remembered dogs now, and USB 2.0 is still very much alive. USB-C has a total of 24 pins, 12 on each side (OK, 22 pins, but let’s not get too bogged down in the details). In the middle is one D+/D pair, this is the data connection of a typical USB 2.0 cable and is mandatory for USB-C. This ensures that all cables will have at least some connection.

USB Type C cable terminal.
USB Type C cable terminal.

USB 3 has added an additional pair of cables for data transfer – there are four more pairs in the USB-C plug. While USB 2 is limited to 480Mbps, the extra tethering of the USB-C cable allows transfer speeds of 10, 20, 40 and even 80Gbps.

Quick note: The USB-C connector is used by USB, of course, but also by Thunderbolt. This distinction is set to disappear because USB 4 is based on Thunderbolt 3 and the new USB 4 version 2 is based on Thunderbolt 4.

Another interesting application is carrying PCI-Express signals – basically a wired version of the PCIe slots on a computer’s motherboard. This made it possible to connect external GPUs to laptops with a single cable.

Video

Another common use for USB-C is for video output. DisplayPort is probably the most common use and USB-C has mostly replaced the big old DP port. Most importantly, it’s not data or video, it’s data, video, and power.

This allows one 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 microphone jacks, and so on. Get a full desktop experience with a single cable connection.

Flashback: USB-C, the one cable that rules them all

This is very useful for laptops, of course, but many smartphone makers offer desktop modes — Samsung’s DeX, Motorola’s Ready For, and Huawei’s have them too. Even Apple has one, Stage Manager for the iPad Pro (which uses USB-C, of ​​course).

Other options besides DisplayPort, MHL, and HDMI adapters are also available. Some of these are active converters that convert from one standard to another, but there are simple passive converters as well.

My voice

We’ll mention the sound here quickly. USB can drive an external DAC that you can connect headphones to. However, as with video, there is also a negative option – audio adapter accessory mode.

USB-C has a lot of pins to work with and a few of them can be remapped onto the cables needed for a typical TRRS jack, so a simple passive adapter can connect a headset with a microphone. Note that this is a purely analog mode and that the digital circuits are separated to avoid noise.

Power

The basic USB standard has very low power limits (500mAh for USB 2.0), though most manufacturers don’t follow the standard to the letter, so 10W adapters are very common.

Of course, manufacturers want their products to stand out and fast charging is one way to do that, especially now that smartphone batteries have a capacity of 3-6000mAh. This led to several 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 initial version described several voltages and current levels that could be supported – 2 amps at 5 volts, as well as 3 amps or 5 amps at 12 volts or 20 volts. This gave Power Delivery a very wide range from 10W to 100W.

However, these constant voltages require DC to DC conversion inside the phone to make it more suitable for the lithium battery inside. USB-PD Revision 2 offered more voltages – 9V and 15V – but it wasn’t enough.

Version 3 allows devices to talk to their chargers and request a specific voltage. It can range from 3.3V to 21V and can be accurately dialed in steps of 20mV. Chargers that support this are marked “Programmable Power Supply”. This way the charger is the one dealing with the extra heat, not the phone (lithium batteries don’t like it when things get hot).

Face constant source Programmable power supply
constant voltage mode 5 volts
9 volts
15 volts
20 volts
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 no one 20 mv nominal
current limit setting no one Yes, nominal 50 mA steps
Rotating RDOs during operation No – not applicable Yes, it is required to run PPS
Requires robust outlet design yes yes

The latest USB-PD Extended Power Range standard adds more constant voltages – 28V, 36V, and 48V. This capped the new 240 watts of power (48 volts at 5 amps), enough for even powerful laptops (although phones are already close to the 240 watt 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.

Flashback: USB-C, the one cable that rules them all

Note that for safety reasons these robust cables require a chip called an “electronic tag”. This chip indicates to the charger and to the phone (or laptop or whatever) that the cable is capable of carrying the extra power.

Some criticism

As much as we love USB-C, we can’t pretend it’s perfect. Our main complaint is that while there are so many capabilities, not all devices and not all cables support everything. A lot of the features we mentioned above are optional.

The worst part of it is that it can be very difficult to know which devices and which cables support what. USB-IF tries to smooth things out with new labels that clearly indicate how much data and power a given cable can carry.

This should also fix our other complaint, the naming system has grown to be an absolute beast. Did you know there is no USB 3.0 anymore? USB 3.1 Gen 1 has been relaunched. But that’s no longer there either, it’s USB 3.2 Gen 1 now.

Things are getting trickier with titles like USB 3.2 Gen 2×2. Ugh. Fortunately, all of that will be replaced by more straightforward labels: USB 5Gbps, USB 10Gbps, USB 20Gbps, USB 40Gbps (and USB 80Gbps should be soon). Much better.

Flashback: USB-C, the one cable that rules them all

As for power, there will be two levels – USB 60W and USB 240W. There will be no 100-watt label because the difference between 100-watt cables and 240-watt cables seems small enough that by the time the new labels go live, it won’t make sense to sell 100-watt cables anymore.

Flashback: USB-C, the one cable that rules them all

conclusion

USB-C was great – we use it to charge phones, laptops, headphones, razors, flashlights, and anything else that has a battery in it and fits in a backpack.

It has allowed us to create comfortable workplaces in our offices with monitors, keyboards, mice, etc. all brought to life with a single cable connection. And given that the latest standards allow it to carry a lot more data and power than the original specification, it’s possible that USB-C hasn’t been developed yet.

Will there be USB-D? Maybe, but not anytime soon. Will the world drop cables and go wireless? Probably not – it’s not an efficient way to charge. It’s not great for data, as 2.4GHz Wi-Fi is already painfully crowded in apartment buildings and 5GHz is crowding out too, prompting the Wi-Fi Alliance to move to the 6GHz band.

For the foreseeable future, USB-C is the one cable that rules them all.

Leave a Comment