I found USB standards and related buzzwords have evolved into a state beyond my comprehension and memory over the years. Below are notes to myself and will be updated when new information is available or standards updated. If you also find them helpful, perhaps you could let me know.
The table below summarizes release dates and data speeds of USB standards from the past two decades.
|USB 1.0||1996||Low Speed 1.5 Mbps; Full Speed 12 Mbps|
|USB 1.1||1998||Full Speed 12 Mbps|
|USB 2.0||2000||High Speed 480 Mbps|
|USB 3.0||2008||SuperSpeed 5 Gbps|
|USB 3.1||2013||SuperSpeed+ 10 Gbps|
|USB 3.2||2017||SuperSpeed+ 20 Gbps|
Note that when USB 3.1 came out, maximum speed of USB 3.0 was renamed. When USB 3.2 came out, there were changes yet again. The new Type-C connector is a notable of USB 3.2. The two tables below summarize name changes in USB 3.1 and USB 3.2 releases respectively.
|Original in USB 3.0||New in USB 3.1||Data Rate||Encoding|
|USB 3.0 SuperSpeed||>||USB 3.1 Gen 1 SuperSpeed||5 Gbps||8b/10b|
|USB 3.1 Gen 2 SuperSpeed+||10 Gbps||128b/132b|
|Original in USB 3.1||New in USB 3.2||Data Rate||Lanes||Encoding|
|USB 3.1 Gen 1 SuperSpeed||>||USB 3.2 Gen 1x1 SuperSpeed||5 Gbps||1||8b/10b|
|USB 3.1 Gen 2 SuperSpeed+||>||USB 3.2 Gen 2x1 SuperSpeed||10 Gbps||1||128b/132b|
|USB 3.2 Gen 2x1 SuperSpeed+||10 Gbps||2||8b/10b|
|USB 3.2 Gen 2x2 SuperSpeed+||20 Gbps||2||128b/132b|
For a long time, power supplied over USB was very simple, 500mA @ 5V with a maximum 2.5W. Then came "Battery Charging 1.1" and later evolved into "Power Delivery 1.0." Here are the major milestones in the evolution process:
|Standard USB 2.0||5V, 0.5A; 2.5W|
|Standard USB 3.0||5V, 0.9A; 4.5W|
|Standard USB 3.2 Type-C||5V, 3A; 15W|
|USB Battery Charging 1.1||2009||5V, 1.5A; 7.5W|
|USB BC 1.2||2010||5V, 1.5A; 7.5W|
|USB Power Delivery 1.0||2012||20V, 5A; 100W; new 12V, 20V|
|USB PD 2.0||2014||20V, 5A; 100W; new 9V and 15V; 12V optional|
|USB PD 3.0||2017||100W; new Type-C connector|
From Maxim on 'Battery Charging 1.1':
Prior to BC1.1, all USB power ports, when active (i.e., "not suspended," in USB parlance), were classified as either "Low Power" (100mA) or "High Power" (500mA). Any port could also be "suspended," which means nearly off but still able to supply 2.5mA. For the most part, ports on PCs, laptops, and powered hubs (A powered hub is a USB breakout box with its own wall wart for bus power.) are "High Power," while ports on hubs that receive no power other than what is supplied by the upstream USB host are considered "Low Power." Once plugged in, a device is allowed initially to draw up to 100mA while enumerating and negotiating its current budget with the host. Subsequently it might be allowed to raise its drain to 500mA, or it might be held at 100mA. This is detailed in the USB Serial Bus Specification Rev 2.0, section 126.96.36.199.
and again from Maxim on BC 1.2 over BC 1.1:
The USB BC1.2 standard was...provided for battery charging of a portable device that is powered off. It also added provisions for charging dead or weak batteries. It defined three distinct types of USB ports...communicate their power capabilities to USB-powered portable equipment...
PD 1.0 defined five power profiles (table below), up to 100W maximum. Back then existing cables were limited to deliver up to 7.5W. PD-aware cables were required for delivering higher power. Believe those new cables were never popular as PD 1.0 was not commonly available on devices.
|18W||[email protected], [email protected]|
|36W||[email protected], [email protected]|
|60W||[email protected], [email protected], [email protected]|
|100W||[email protected], [email protected], [email protected]|
PD 3.0 is the latest iteration of 'Power Delivery'. It keeps the same four voltages, 5V, 9V, 15V and 20V as in PD 2.0. Below is a graphical summary of voltage-current combinations and their maximum power, from Figure 10-2 in the USB PD Specification v3.0.
Different from previous revisions, PD 3.0 mandates (according to this TI page) that all sources offering greater than
- 15W shall advertise 5V and 9V
- 27W shall advertise 5V, 9V and 15V
- 45W shall advertise 5V, 9V, 15V and 20V.
The new Type-C connector is a signature in USB 3.2. And PD 3.0 is over Type-C only! More from Renesas:
|USB PD2.0||USB PD3.0|
|Connector Type||Type-A, Type-B, Type-C||Type-C only|
|Power Rules||Only when using Type-C||✓|
|Fast Role Swap (FRS)||-||✓|
|Programmable Power Supply (PPS)||-||✓|
|USB Type-C Authentication||-||✓|
For differences in physical and protocol layers, look at this Arrow Devices article.
What are those new features?
Fast Role Swap: for example, consider a tablet is charging a smartphone. With a software toggle on the phone, the roles can be reversed very quickly (within 150us) and now the smartphone can charge the battery inside the tablet.
Programmable Power Supply: it is to reduce power conversion loss or charge a battery more efficiently. For example, a smartphone's charging algorithm can request a PPS-capable power supply to provide constant current charging at the start. When the battery is near full, the algorithm requests the power supply to provide constant voltage charging.
IEC-63002: a standard of communicating identification between two devices. In olden days, the two (and only two in USB) data pins are 'hacked' to assert different voltage levels for serving this role. Now Type-C provides two new and dedicated data pins for this purpose.
Type-C authentication: in other words, akin to the 'special chip' in Apple's lightning cable.