top of page

USB cables, testing

Table of contents

Measurement equipment used for USB cable testing

 

Measuring devices (USB testers):

  • Power-Z KM003C (firmware version 1.9.9)

  • FNIRSI FNB58 (firmware version 1.03)

  • Treedix USB cable tester

  • BitTradeOne USB Cable Checker2

​​

An overview of USB testers used, including for testing the USB cables presented below, as well as a comparison of fast charging protocols using KM003C, FNB58, and KOWSI KWS-X1 can be found on a separate page.

⇧ to the table of contents ⇧

USB cable parameters. eMaker chip, USB protocol

​​​

  • eMaker chip - this is a special chip inside the usb-c plug which takes part in communication between a charger and a charged device (or between two connected devices). eMaker chip does installed for the 60W cables (maximum current is up to 3A by PD charging protocol default). The eMaker chip sends information to charger and connected devices about cable characteristics like:

    • Supported charging protocol (including max.current and voltage). This is how a charger could distinguish cable maximum power: 60W(up to 20V3A) vs 100W (up to 20V5A) vs 240W(up to 48V5A) and determines proprietary cables.​

    • Thunderbolt technology support and its version. Since Thunderbolt version 3 this technology exploits UsbC cable type. There are a few articles I can advise: Thunderbolt 4 vs USB4 and Thunderbolt 4 vs. Thunderbolt 3 vs. USB4 vs. USB 3 and announcement of Thunderbolt 5, First Batch of Thunderbolt 5 Devices Launched.

    • Display port alternating mode (over UsbC), supported starting from USB3.1 cables, but for a USB port on a device the special Display Port marking must be present or the port must be TB3/4/5 or USB4 compatible. Here is the article about that technology.

    • USB protocol (USB 2.0/3.0/4 etc.). The transmission speed, for example, depends on it.

    • Passive or Active cable. The Active cables have a special circuit to boost the signal in order to support high-speed transmission in long cables because the signal quality is degrading due to interferences from surroundings.

    • Chip vendor.

    • If you want more information about eMaker chip you can read this article.

  • USB protocols. There are many USB protocols on the market, starting from USB2.0 (480mbps data transmission speed) up to USB4 2.0 (80Gbps data transmission speed). You can read this article to get more information about protocols and markings.

  •  Article about data bandwidth needed for different screen resolutions and frequencies through DP (Display Port) which signal can also be sent over UsbC cable.

  • HDMI, DP, DP Alt mode on USB-C bandwidth calculator.

  • Here you can find an article about UsbC pinout.

  • Here is the official cable and connector specification for UsbC cables.​

  • Early versions of USB4 cables did not include instructions that made them fully compatible with TB3 devices at full 40Gbps speed (it was limited to 20Gbps). Details can be found in this Reddit post.

  • Here is you can find the official USB certified list of cables (USB-IF EU Conformity (IEC 62680)).(but it could not be a comprehensive list)

  • List of campaigns supporting membership in the USB association.

⇧ to the table of contents ⇧

USB cable types for fast charging

​​​

Not all cables can be used in quick/fast charging because cable producers might use inside cable only power and ground lines (VCC and GND) and ignore data lines. These cables can to be used in basic charging protocols like CDP, SDP, DCP (up to 1.5A) because higher voltages and more sophisticated charging protocols require data lines to negotiate them. That is why sometimes identically looking cables can or can't do fast charge.

​

In this test I am focusing on several cable types that are using in quick/fast charging:

  • UsbA-micro USB - can support QC (Quick Charge).

  • UsbA-UsbC - these cables are more advanced and can be used in many charging protocols including proprietary ones from OPPO/OnePlus/Realme, vivo/iQOO, Xiaomi/Redmi/POCO. These cables might have eMaker chip, reinforced power pads for high current charging (10A for example) and an additional contact for activating proprietary charging.

  • UsbC-UsbC is the most advanced type of USB cable. The cable is universal and “externally symmetrical” (the male plug is not electrically symmetrical, but this does not affect the connection orientation), has multiple data lines and double power lines, can be used for standard charging protocols such as QC or PD (power delivery), as well as for proprietary protocols from Xiaomi, vivo and other manufacturers, as well as for advanced data transfer (USB4, Thunderbolt 3/4/5, DisplayPort video transmission). In such cables, there may be an eMaker chip that tells connected devices whether the cable meets a certain PD standard and power (100W/240W), proprietary charging protocol support, data transfer speed, Thunderbolt version and other specific parameters. Please note that sometimes cheap USB-C cables are orientation-dependent, so you may notice a difference in charging or data transfer depending on how you connect the cable, but this is a violation of the USB standard, and if you have such a cable, it is better not to use it.

​​

It is also worth mentioning some widely used USB-C (PD)-DC cables:

  • USB-C-MagSafe3

    • This type of cable is used by Apple to charge certain laptop models. The cable contains electronics capable of triggering the required PD protocol (5, 9, 12, 15, 20, 28V with a current of up to 5A) from any PD-compatible power adapter, not just the original Apple one. PD-compatible power adapter, not just the original Apple one. Thus, Apple laptops equipped with a MagSafe3 charging port can receive up to 140W of power from a PD3.1-compatible charger, such as the AOHi Magcube 140W 2C1A.

  • USB-C to Lightning

    • Cable for Apple iPhone, provides charging for compatible iPhones with an actual power of about 22W, uses the standard PD protocol 5V and 9V.

  • UsbC-DC (5.5x2.5/2.1)

    • These cables have an e-maker chip on the USB-C connector side that is set to a fixed voltage according to the PD protocol. You can find such a cable for any PD voltage: 5, 9, 12, 15, 20, 28V 3A/5A (for example). This type of cable might be handy as a replacement of old AC-DC adapters up to 5A.

  • There are other cables and adapters that use a USB-C connector, you can find more details here.

⇧ to the table of contents ⇧

Cable resistance measurements

​​​

The cable resistance is a very important factor for charging cables (for data transmission it does not really matter) which influences charging efficiency and voltage drop on the cable, because due to internal cable resistance (in wires and in plugs). Part of the energy from a charger to a charged device is losing and dissipating heat because of the cable resistance. As the higher electrical current flows, the more will be energy losses. That is why USB cables designed for high current charging (like SuperVOOC, Hypercharge etc.) are usually thicker. You can also notice the cable resistance effect as your smartphone gets fewer volts than charger supplies (for example 8.4V instead of 9V). If the resistance is too high (>800mOhm) the cable or plug could be hot or it could even be dangerous to use. Also, power losses in a cable are especially unwelcome for portable charging devices like power banks, solar battery charges, where every drop of energy counts.

​

Requirements for USB-C cable resistance (passive or active) according to USB standards:

IR (voltage) drop limit along the line VCC<0.5V, GND<0.25V (total 0.75V)

This means that for USB-C cables rated for 3A (60W) current transfer, the maximum resistance is 250mOhm, and for cables rated for 5A (100W/240W), the maximum resistance is 150mOhm.

​

The resistance requirements for USB-A to USB-B cables are not defined in the same way as for USB-C, but there is an indication that the maximum voltage drop is 0.25mV at a load of 500mA. ECN requirements also specify voltage drops across VCC+GND lines as 0.125mV+0.125mV, as well as allowing power sources to set 5.5V at the output.

The above specifies a cable resistance of 500mOhm for currents of 500mA.

​

However, USB A/B cables can also transmit higher currents up to 1.5A (DCP protocol), which leads to the conclusion that, in an ideal scenario, a USB A-B cable should have a resistance of 170mOhm. but considering that the source can overstate the voltage up to 5.5V, we can conclude that cables with a resistance of up to 350mOhm are acceptable for use.

​​

So, what should the resistance of a USB cable be?

USB-A-C, USB-C-C:

  • 60W(3A) <=250mOhm

  • 100W/240W(5A) <=150mOhm

UsbA-B:

  • 0.5A <=500mOhm

  • 1.5A <=170mOhm (preferable) and <=350mOhm (acceptable)

​​

FNIRSI FNB58 USB-tester device measures cable resistance as a difference in voltages between two measurements: direct connection to a power source and connection to the same power source but through the cable. The measurement will only be correct if an external load is used while both measurements are performed.

I am using a stable external load with fixed resistance 8Ohm and 100W heat dissipation capability (it is possible to use less powerful resistor) connected to UsbA plug. This resistance pulls 625mA of current at 5V.

FNIRSI FNB58 has only UsbA male plug for direct measurements, so in order to measure UsbC-UsbC cables, I am using Logitech UsbC-UsbA adapter which has the lowest possible resistance impact on measurement (it was chosen among 5 different adapters of that type).

​​

With the availability of the BitTradeOne USB Cable Checker2 tester, I use it for the purpose of testing the resistance of UsbC cables because the process is much simplified and accelerated. To the measurement results I apply the correction of the error of 60mOhm (reducing value), which is revealed in comparison with the results of Fnirsi FNB58.

⇧ to the table of contents ⇧

Other USB cables and USB adapters worth mentioning

UsbC-UsbC USB IF certified 4m (13ft) cables:
​
UsbC-UsbС сables/adapters

​

UsbA-UsbC (UsbC-UsbA) cable/adapters

​

UsbA-UsbA cable/adapters

​

UsbC-micro USB cable/adapters

​​​

USB-DC cables/adapters

  • USB-C PD to DC adapter(cable) (AliExpress) - I use the 12V and 20V versions of this cable for the purpose of replacing a separate AC power adapter for home appliances with a more reliable UsbC adapter or universal multi-port USB adapter.

  • USB Type C to DC 20V 3A PD Emulator Trigger silicone cable 1.5m - I have bought this very flexible heat resistant cable to power my TS100 soldering iron directly from USB-C multi-port adapter.

  • USB-C to DC Cable PD3.1 140W (28V5A)(Amazon) (AliExpress) - 180cm cable 90degree DC jack 5.5*2.5mm
  • UsbC-DC PD trigger (decoy) board(Amazon) (AliExpress) - a small board on which you can use switches to select the desired voltage to be supplied to the DC output (5V, 9V, 12V, 15V, 20V). Keep in mind that if the UsbC source cannot supply the desired voltage, the DC output will be supplied with the lowest voltage possible, e.g. if the adapter does not support PD12V, it will send 9V to the board's input even though the board has requested 12V.
  • UsbA-DC 12V Braun shaver charger (Amazon) (AliExpress) - A very handy cable to charge your Braun shaver instead of using a separate charging adapter. I use it when traveling, it's lighter and takes up less space​
  • ​UsbC-Lenovo slim tip(Amazon) - 20V5A (100W) adapter for Lenovo laptops. If your notebook does not require more than 100W of power, you can replace the original power adapter with any other one that has support for PD3.0 standard or higher and power of 100W or more, UsbC-UsbC cable with rating 5A(100W) and this adapter.​
  • USB-C laptop tip. 20V5A-100W. Excellent adapters for charging laptops with a power of up to 100W. A large selection of plugs for different laptops. I have personally tested and use adapters for Lenovo and ASUS.

​

​​

USB - HDMI, USB-DP, USB-AUX adapters

 

USB data blockers

Data blockers are devices that are installed between the cable and the charger to allow fast charging while preventing data transfer. This functionality ensures the safe use of USB chargers in public places (airports, bus stops, park benches, etc.), preventing your device from being tampered with.

⇧ to the table of contents ⇧

Support TinkerVault
Some links on this page might be affiliate links. This means I may earn a small commission if you make a purchase through these links, at no extra cost to you.
I buy and test every product ourselves to provide honest, unbiased reviews - your support helps me keep this project alive and independent.

Thank you for being awesome!

bottom of page