USB Power Delivery and Data Transfer Standards

Due to the complex amount of information available, we have researched and extracted the more recent and relevant portion of the USB power and data transfer specifications from Wikipedia and USB-IF for ease of reference.

There are confusions when manufacturers do not write their specifications clearly, for example, when they write USB 3.1, do they mean USB PD 3.1 (power supply specifications) or USB 3.1 (data transfer specifications). These specifications refer to two different standards and are not directly related.

Below are the two tables summarizing the recent USB power supply and USB data transfer standards. In general, if the acronym “PD” is missing from the specification, then it should refer to the USB data transfer standards which are Table 2 below.

Table 1: USB Power Delivery

SpecificationPort
CurrentVoltageMax. Power
Power Delivery 1.0Micro-USB3A20V60W
Power Delivery 1.0USB-A/B5A20V100W
Power Delivery 2.0 and 3.0USB-C5A20V100W
Power Delivery 3.1USB-C5A48V240W

USB PD 3.1 was released on 24 May 2021 on the USB-IF website.

Source: Wikipedia – USB hardware

Without the USB Power Delivery, USB connection provides a lower power as follows:

Table 1a: USB Power Supply Without PD

PortVoltageCurrentPower
USB 2.0USB-A5V0.5A2.5W
USB 3.1USB-A5V0.9A4.5W
USB BC 1.2?5V1.5A7.5W
USB-C 1.5A
(Rev 1.0 to 2.1)
USB-C5V1.5A7.5W
USB-C 3AUSB-C5V3A15W

Table 2: USB Transfer Speed Table

USB VersionYearMax Transfer SpeedPortRemarks
USB 1.019961.5 Mbps (0.1875 MB/s)USB Type AFull speed
USB 2.02000480 Mbps (60 MB/s)USB Type AHigh speed
USB 3.020085 Gbps (500 MB/s)USB Type A/ CSuperspeed (8b/10b)
USB 3.1 Gen 120135 Gbps (500 MB/s)USB Type A/ CSuperspeed (8b/10b)
USB 3.1 Gen 2201310 Gbps (1,212 MB/s)USB Type A/ CSuperspeed+ (128b/132b)
USB 3.2 Gen 120175 Gbps (500 MB/s)USB Type CSuperspeed (8b/10b)
USB 3.2 Gen 1×2201710 Gbps (1,000 MB/s)USB Type CSuperspeed+ (8b/10b), 2 lanes
USB 3.2 Gen 2201710 Gbps (1,212 MB/s)USB Type CSuperspeed+ (128b/132b)
USB 3.2 Gen 2×2201720 Gbps (2,424 MB/s)USB Type CSuperspeed+ (128b/132b), 2 lanes
USB 4 Gen 2201910 Gbps (1,250 MB/s)USB Type C
USB 4 Gen 2×2201920 Gbps (2,424 MB/s)USB Type CUSB4 20Gbps (64b/66b)
USB 4 Gen 3201920 Gbps (2,424 MB/s)USB Type C
USB 4 Gen 3×2201940 Gbps (5000 MB/s)USB Type CUSB4 40Gbps (128b/132b)
usb-highspeed-logo
USB Highspeed Logo
usb-superspeed-5-gbps-logo
USB Superspeed 5 Gbps Logo
usb-superspeed-plus-10-gbps-logo
USB Superspeed Plus 10 Gbps Logo
usb-superspeed-plus-20-gbps-logo
USB Superspeed Plus 20 Gbps Logo
usb4-40gbps-logo
USB4 40Gbps Logo
usb4-40gbps-trident-logo
USB4 40Gbps Trident Logo

Source: Wikipedia – USB

USB Type-C™ and USB-C™ are trademarks of USB Implementers Forum.

Table 3: Thunderbolt

Thunderbolt verYearMax SpeedPortRemarks
Thunderbolt  110 Mbps (0.1875 MB/s)Thunderbolt
Thunderbolt  2201320 Gbps (2,424 MB/s)Thunderbolt
Thunderbolt  3201540 Gbps (5000 MB/s)USB Type CSupport DisplayPort 1.4, 1x4K display at 120Hz or 2x4K display at 60Hz.
No USB 4 support
Thunderbolt  4202040 Gbps (5000 MB/s)USB Type CSupport USB4
The rest same as Thunderbolt 3.

Thunderbolt is the brand name of a hardware interface for the connection of external peripherals to a computer. It has been developed by Intel, in collaboration with Apple.

Note that not all USB Type-C support Thunderbolt unless explicitly stated by the device manufacturer.

The older Thunderbolt 1 or 2 ports are supported by some older devices such as Surface Pro, as well as high-end workstations notebook for backward compatibility. They are also useful for connecting to external HDMI and 4K displays

thunderbolt-1-and-2-port
Thunderbolt 1 and 2 Port

Source: Wikipedia – Thunderbolt

Notes

The read/write speed of a typical 7,200 rpm HDD is 80-160 MB/s, and SSD starts at 550 MB/s, and up to 5,000-7,000 MB/s, such as the Samsung 980 PRO PCle 4.0 NVMe M.2 SSD. Based on the above table, it requires at least a USB 4 Gen 3×2 to fully utilize the high read and write speed of the fastest SSD in the market.

USB-C Advantages

The USB-C or USB Type C is the preferred connector for both data and electrical power. It has high power delivery and data transfer rate and has replaced the micro-USB on most, if not all consumer electronics device and gadgets. It is both surprising and frustrating that iPhone Pro 12 is the only high-end device in the market that has yet to adopt this standard connector.

USB-C should be a key design requirement that everyone should look out for when deciding on their next purchase. Users will only need to have one type of cable to support all devices for both data and power transfer. The most important reason is that having USB-C means your device is “future proof”. So if your device still does not have USB-C in 2021, it is technically classified as outdated.

Other than power delivery, high data transfer rate, USB-C does not have any up or down orientation requirement like the older micro-USB standard. It is easier to plug in even in the dark as long you can locate the port by touch.

In terms of size, USB-C is slightly larger than the micro-USB Connector, however, it does not appear to affect the size of peripheral device design yet. Unless a 5mm thin phone comes along, then perhaps the USB-C might feel too big.

There may be a need to focus on safety as the power delivery output increases. The “USB” cable no longer delivers just low DC power for data and charges the mobile phone. At 240W, these cables should be treated with care like any existing notebook power cables and adapters. Never trade safety for cheap and unqualified design.

New USB-C PD Review 3.1

USB-C will only get better. In May 2021, USB-IF published the details of a new USB PD Revision 3.1 specification that increases the PD (Power Delivery) via USB-C (aka USB Type-C) from 100W (20V 5A) to 240W (48V 5A). USB-IF published the USB-C Cable and Connector Design Specification Revision 2.1, which include the reference design and guide for implementation.

The new standard is called the Extended Power Range (EPR), which manufacturers would need to comply to produce new cables that are EPR-certified to deliver 240W (48V 5A) power supply.

So what does this mean for the consumers like us?

  1. USB-C connector could be used to power up almost all power notebooks, and including the high-end gaming laptops with powerful discrete graphics cards.
  2. One standardized, universal connector (jack) for all notebooks and laptops. There will be no need to worry about power adapters from different brands with different power ratings. Everyone can share the same type of cable.

One point to note is that USB-C design revision 2.1 (EPR) deals with the power delivery only, whereas the data transfer rate for USB-C connectors and cables is currently using USB 3 standard.

In 2017, USB 3.2 standard was released specifically for USB-C, and the current highest transfer speed is USB 3.2 Gen 2×2 – SuperSpeed+, new 20 gigabits per second (Gbit/s) data rate over 2 lanes using 128b/132b encoding (effective 2,424 MB/s).

USB 4.0 announced in Aug 2019, could potentially push the transfer speed up to 40 Gbps!

Will the “Power Brick” Finally Disappear?

It is already happening, especially with the 200W GaN Chargers already in the market. These pocket-sized and lightweight chargers are only delivering up to 100W per USB-C port at this time of writing, and we are expecting higher power ratings in the near future.

In June 2021, Xiaomi has announced the patented Xiaomi Hypercharge that can deliver up to 200W wired and 120W wireless. We should be expecting 240W chargers coming soon next few years. One of our concerns is related to safety, such as the USB wire design and the connector to support 240W of power.

All existing USB-C PD Chargers have built-in AC/DC converters since the mobile devices use DC current.

If the USB-C can delivery 240W safely to laptops, then all the different brands of laptop should be able to use the same USB-C cable and charger in the future.

 

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