First Look

USB, Thunderbolt and Power Delivery for Dummies


There are now so many so-called standards for USB, Thunderbolt and Power Delivery that we have updated our guide – my how it has changed over a year.

USB, Thunderbolt and Power Delivery for dummies covers from USB 1.0 to the new USB-4 and the confusing power delivery (PD), battery charging (BC) and Quick Charging (QC) standards (and they are not the same things).

In preparing the USB, Thunderbolt and Power Delivery for Dummies, it was not a matter of looking up a Wiki (wish it were) but consolidating USB standards and battery power standards.

  • USB-A (and variants) – As USB-A should be on the way out now our best advice is to look for USB-C devices.
  • USB-C is a little easier. Well, it was more difficult this time due to the new USB-4 standards (not yet seen on any device). And it seems some manufacturers are pushing the standards as well. For example, USB-C can have a PD from 10W to 100W, but it depends on cable ratings!
  • Thunderbolt 3 is much easier – there is only one standard but several cables. Intel is the guardian of Thunderbolt and has given it’s standard free (without royalty) to the world. Basically, it means all Thunderbolt 3 devices are interoperable.
  • BC is about charging batteries (mainly USB-A)
  • PD is about using USB-C for data and power delivery
  • Fast charge is how fast you can fill the tank (Mainly USB-C)

USB, Thunderbolt and Power Delivery for dummies

USB, Thunderbolt and Power Delivery

Note 1Mbps = .125MBps = .001Gbps or .000125GBps.


Note: Half-Duplex (HD) can send or receive data but not at the same time (think of a single lane bridge where a car has to stop to let another through), so it achieves about half the speed. Full-Duplex (FD) means it can send and receive data (two lanes) at the same time only losing a small amount of speed.

USB-A only (includes micro-USB and mini-USB connectors and variants).

  • 1.0 – up to 12Mbps (HD) – black keyed port and cable up to 5 metres
  • 2.0 – 480Mbps (HD tops out at 280Mbps) – ditto
  • 3.0 – 5Gbps (FD tops out at 3.2Gbps) – blue keyed port and cable to 3 metres

USB-C (3.1 can also use some USB-A blue keyed ports)

  • 3.1 Gen 1 – 5Gbps (FD with the right SuperSpeed cable)
  • 3.1 Gen 2 – 10Gbps (FD with the right SuperSpeed+ cable)
  • 3.2 Gen 1 – 5Gbps
  • 3.2 Gen 2 – 10Gbps
  • and 3.2 Gen 2 2×2 – 20Gbps

USB-4 (based on Thunderbolt 3)

  • Gen 2×1 – 10Gbps with USB3.2, DP1.4a and PCIe tunnelling, Host to host OTG transfers
  • Gen 2×2 – 20Gbps – ditto
  • and Gen 3×2 – 40Gbps – ditto

Thunderbolt 3

USB, Thunderbolt and Power Delivery Thunderbolt 3
  • Usually, 40Gbps over .5m Thunderbolt certified USB-C cables but older implementations and longer ‘passive’ cables will see that reduce to 10 or 20Gbps.
  • Thunderbolt 2 is 10Gbps FD and 20Gbps HD.

Battery charging (BC) Specification (these are not as ‘standard’ as we would like)

Battery Charging (for USB-A only and relates to ‘dumb’ chargers). It is unwise to plug a higher rated charger into a lower-rated device as excess power converts into heat. Conversely, you can use a lower-rated charger, and it takes longer to charge.

In our experience, USB-A chargers come in 5V/.3A (1.5W), 5V/.9A or 1A (4.5-5W), 5V/2A (10A and the limit of micro-USB cables) and 5V/3A (15W and for USB-C devices).

  • 1.0 is 5V up to 500mAh (2.5W) – there is no intelligence, and the charger should match the device amperage needs, e.g. 5V 300mA (1.5A), 5V/500mA (2.5W).
  • 1.1 is 5V up to 900mA (4.5W) – ditto. Also called USB 3.1 gen 1 over USB-C
  • 1.2 is 5V up to 1.5A (7.5W) – ditto. Also called USB 3.1 gen 2 over USB-C
  • We have seen a lot of USB-A, 5V/2.4A and 5V/3A (12-15W) chargers and these are outside BC standards – more the PD 1.0 standard below. Do not use these with older USB devices.

Generally, USB-A self-powered (bus-powered) devices (using the USB-A 2.0 host or later) draw 5V and from 100mA-1000mA (.5W to 5W).

Obviously, the BC protocol ran out of ‘steam’, and USB-C PD came into play.

Power Delivery (PD) over USB-C (applies to USB-C 3.1 or higher)

PD 1.0 (5V/3A/15W)smartphones and devices USB devices to 15W: This is the most common USB-A to USB-C cables can handle that. If the device does not need the wattage, the charger delivers lower wattage.

US PD is a standard as the charger and device have some intelligence (called a power contract or handshake) to deliver the right voltage and amperage. The only catch is that you need a cable rated for the amperage. You need an EMCA (Electronically Marked Cable Assembly) cable for over 3A. And power can flow upstream (to the device) and downstream (from the device).


You will hear the term ‘fast charge’ bandied around but, it is just pouring (flooding) more wattage into the battery. It is safe, but the jury is out on whether repeated charging shortens battery life.

There are other lower PD standards like 1.5A (12-20V/1.5-3A/18-60W), 3A (12/20V/3-5A (36-60W) and 5A (12-20/5W. 60-100W).  We seldom see them.

PD 2.0 introduced the ability to use fixed voltages from 5/9/15/20V and 3 to 5A (15-100W).

But it is not an elegant standard relying on large voltage, and amperage jumps from say, 20V/3W for the first 30%, dropping to 15W/3A for the next 20% etc. PD 2.0 tops out at 60W without a special cable.

PD 3.0 is 5V up to 20V and 3A to 5A (15-100W). It is a more elegant and universal solution because it allows micro-voltage and amperage steps instead of the fixed voltages. In this way, it can deliver higher voltages and lower amperages.

USB On-the-Go (OTG) simply means ports that can send data/power upstream or downstream. USB-C cables are full-duplex; it is the devices that may be half-duplex.

Fast or Quick Charge (QC) for smartphones (note these do not support data transfer like PD)

A quick refresher: Volts x Amps = Watts (OHMS law), 1000 milliamps per Amp (mA), mAh is the total mA the battery can deliver for one hour.

Volts are a lineal measure of voltage. Amps are how fast that voltage flows into the battery and Watts – well that is the overall volume or charge ability of V x A. Note its not so much the Voltage that can kill a person but the Amperage – 10mA can give you a painful shock and 100-200mAh can kill.

There are a few confusing issues like efficiency and loss due to heat but suffice to say that all smartphone batteries are 3.3V and pouring in 5V will not hurt them.

One final measurement is smartphone battery capacity in milliamp hours or mAh. Simply put a 4000mAh battery can deliver 4A for one hour. If your device had a power draw at idle of say 400mA, then it would drain the battery in 10 hours. Similarly, if you want to charge that battery at 10W (5Vx2A) it would take 2 hours to fill (but the reality is that lower charging efficiencies make that even longer).

From 2019 new Google Android smartphones (to comply with Google Mobile Services) must have a USB Type-C port with full interoperability with chargers that are compliant with the USB-PD 2.0 specifications. Older micro-USB is slowing being phased out except those with lower-powered MediaTek SoCs.

Most, if not all QC technology (except OPPO) uses exponential charging. It floods the battery with the highest volt/amps it will take until about 50% full then steps down to 9V to 75-80% when the standard 5V/2A kicks in. This is to prevent battery fires and help preserve battery life.

USB, Thunderbolt and Power Delivery QC BS

Qualcomm Quick Charge

QC requires a compatible Qualcomm SD SoC and a phone that has a QC charging circuit. Standards are backwards compatible.

  • 1.0 – 5V/2A (10W)
  • 2.0 – 5/9/12 (18W) for latter SD2XX/4XX/6XX up to SD810
  • 3.0 – dynamic 200mV increments 3.6-20V up to 18W – SD4XX to SD821
  • 4.0 – dynamic 20mV increments 3.6-20V/2.5-3A (27W) – SD6XX, 710 and 835 and PD 2.0 compatible
  • 4+ – for SD670, 845/855. PD 3.0 compatible. Introduces Dual charge paths like OPPO VOOC

OPPO (also known as Dash or Warp Charge (OnePlus) and used in vivo and realme

A proprietary solution requires a special dual-channel ‘green’ insert USB-A cable to work with dual batteries; otherwise, it delivers half the amperage. You can use QC compatible chargers, but the maximum is PD 2.0 at 10W.

  • VOOC 2.0: 5V/4A (20W)
  • SuperVOOC: 5V/4A – Find X
  • VOOC 3.0: 5V/5A (25W) for OPPO Reno
  • VOOC 4.0 (not released) is 5V/6A (30W) (also called Warp Charge)
  • Coming 10V/5A (50W)

Huawei SuperCharge

It is a proprietary solution, but QC 3.0 chargers will give reasonable speed. We note that Huawei SuperCharge batteries run hotter than most during charge.

  • V 1.0 – 4.5V/5A (22.5W) for P and Mate 10 series – need purple insert USB-A cable. Also has 5/9V/3A for PD 2.0 compatibility at 27W
  • V2.0 (4.5-10V at 4/4.5/5 – maximum 40W) for Mate 30/Pro – PD 2.0 charges at 27W

Samsung Adaptive Fast Charge

Since the Note7 issue, Samsung has been ultra-cautious about battery pedigree (build) and fast charging. In all our tests, Samsung phones maintain the lowest battery temperature, and we think that is best. Note that all chargers support similar Qualcomm QC 2.0 or 3.0 standards as the phones can use Exynos or Qualcomm chips depending on the market.

  • 5/9V and 2A (18W) for its older Galaxy/Note series phones (QC 2.0)
  • 5/9 and 3/2.77A (25W) plus PD 3.3/5.9/3A and 3.3/11/2.25A (28W) for Galaxy 10 5G (QC 3.0)
  • 5/9/12V and 2/1.67/2.1A for its tablets PD 2.0
  • The Note10+ can use a special 10V/4.5A (45W) charger, but if you use QC 3.0 or 4.0 chargers it only charges at 27W.

Motorola TurboPower

Motorola’s TurboPOwer is more a marketing term and it basically QC 2.0 in disguise unless using a MediaTek SoC.

  • 15 is 9/12V and 1.2-1.67A (15W)
  • 25 is 5/9/12 and 2.15-2.85A (25W)
  • 30 is 5V/5.7A (28.5W) – Motorola needs to use batteries that can handle the Amperage.

MediaTek Pump Express

MediaTek has QC 2.0 compatible charging on some of its chipsets.

  • 2.0+ is 5-20V in .5V increments 3-4.5A (maximum 15W) – works with Micro-USB cables to 10W
  • 3.0 is 3-6V in 10-20mV increments 5A (25-30W) – USB-C only and three-stage – Regular, Turbo 1 (, and Turbo 2 (6V/2A/15W) – PD 2.0 compatible
  • 4.0 is 3-6V (10-20mV increments 5A (25-30W) – supports 15W Qi charger. PD 1 compatible

GadgetGuy’s take – USB, Thunderbolt and Power Delivery is a whole lot of mumbo jumbo

We put this reference together a year ago because we get so many claims about fast charging or USB-C PD that we needed to develop a reference, free from marketing BS.

Boy, has a lot changed. One thing has become evident – power is the lifeblood of any device and the alibility to recharge it quickly is paramount to users.

In fact, we have seen in recent tests where a 5V/3A charger (15W) meets or beats a so-called fast charger to 100%.

In most cases, there is more marketing hype than reality in smartphone fast charge claims. Most start by claiming, for example, 50% in just 30 minutes neglecting to tell you that the battery has been flood charged at say 15V/4A (60W) and any more would risk thermal burnout. Fast charge is a three or even four-stage charge.

Please note that should you find any errors please let me know – there are a lot of numbers here.