What is the difference between 3A and 5A cable?

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    In recent years, the power of digital products has developed from 5W to the current 240W. The interface specifications, cables and chargers have undergone great changes. On the surface, they are all USB-C charging cables, the price can be several times different, and often because the wrong charger is used, the charging power will be greatly reduced. This has to mention that the standard usb-c cable has a “performance grading” system in terms of charging, the most common are 3A and 5A specifications.

    Now let’s introduce why two kinds of cables affect the charging power from this aspect?
    USB-C is the most common interface at present, but it also includes three types: USB-C to USB-C, USB-A to USB-C, and USB-C to Lighting. Since C to Lighting is not a universal cable, we will not discuss it here.

    According to the USB specification, it can be known that in the USB PD/USB-C point-to-point connection system, there are three participants, the power supply device (source), the power receiving device (sink), and the cable. In each connection, in order to avoid blind people touching the elephant, the devices will conduct “information negotiation” through the cable to know whether the other end of the cable is a mobile phone, a charger or a computer. Determine whether the other party is a power supply device or a power receiving device, and communicate key information such as power supply specifications, power receiving specifications, and data transmission rate specifications. The cable is an important bridge for carrying information communication and participating in power transmission, and an “E-marker” chip can be added to the connector. Participate in the information negotiation as a third party, but not all “E-marker” chips are available. For cables without “E-marker” chips, the current is limited to 3A for safety reasons to avoid high resistance and high current overheating. Safety issues, and the cable using the 3A “E-marker” chip, the maximum current transmission is also 3A. Only 5A “E-marker” chip, the maximum current transfer can reach 5A.

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    It can be seen from the table that the maximum current transmission specifications of the data cable are mainly divided into two types: 60W/100W is divided into 3A cable /5A cable according to the current.
    Except for the Thunderbolt data cable, the power transmission performance of other data cables is not directly related to the data transmission performance. If you want to obtain a fast charge of more than 60W, a 5A cable is necessary. If you buy the wrong one, the power will be limited, so pay attention. 3A cable is the most common on the market, and there is no obvious mark on the appearance. Literally understand that the maximum transmission current value is 3A. Based on the calculation of the maximum voltage of USB 3.0 at 20V, the maximum charging power is 60W. Generally, the “E-marker” chip will not be added to the 3A cable. Design specifications. Of course, 60W is enough for ordinary mobile phones, tablets, Switch game consoles, and ultrabooks, and the price is relatively low. Many devices below 60W are equipped with 3A cables as standard.


    Compared with 3A cable, 5A cable has higher current transmission specifications and more stringent requirements in all aspects. In terms of appearance, “5A” is generally marked on the packaging and joint parts for easy identification. The calculation is based on the maximum voltage of USB PD3.0 20V, the maximum power that can withstand is 100W, and the 5A cable must have a built-in 5A “E-marker” chip. In the process of “information negotiation” between the power supply equipment and the power receiving equipment, the key parameter that the cable supports 5A is obtained, and the entire fast charging system can break through the 3A limit. The production, design and manufacturing process of 5A cable are more complicated, the joint is thicker gold-plated, the shrapnel is wider, the cable core is thicker, and cotton cable, lubricating powder, etc. are usually added to improve flexibility and avoid the cable body being too hard. 100W fast charging can be used for flagship mobile phones, high-performance notebooks, large power banks and other devices with higher requirements. In terms of price, manufacturers are more willing to spend time on the design of the appearance on the 5A cable. Improve product durability, of course, the price is higher.

    We have tested the electrical performance of a number of cables before. In the voltage drop internal resistance test, we can see that the resistance of the two 5A cables is as low as 0.06Ω, which is much lower than other ordinary cables. The voltage drop is lower, the energy loss is less, and it is not easy to heat up.

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    In addition, we have collected some frequently asked questions to answer,
    Q1: Can 3A cable and 5A cable be mixed?
    A1: In most cases, it can be mixed, mainly because the power will be limited to 3A after using 3A cable. For example, the power of 20V 5A fast charge is only 20V 3A. There are also individual notebooks that have stricter requirements. The charging power requirement is 20V 3.25A, which means that it must be equipped with a 5A cable. Some notebooks even detect 20V 3A and refuse to charge.

    Q2: 5A cable is so good, is 3A cable still worth buying?
    A2: Only buy the right one, not the expensive one, just choose the right one according to the equipment you have. 5A cable is mainly used for high-power and high-current equipment. The cable body is thicker and harder. 3A cable is easier to store and cheaper.

    Q3: Why is 5A cable rarely seen in super-long styles such as 2 meters?
    A3: Generally speaking, the ultra-long cables of two meters and three meters on the market are 3A cables, and 5A cables are usually only 0.3-1M, because the longer the cable, the greater the resistance value, resulting in a greater voltage drop, and high current is fast. Charging will also consider the voltage drop value. Therefore, 5A cable generally does not appear super long cable.

    Q4: Do you have to buy a 5A cable to support 5A current?
    A4: Generally speaking, whether it is a USB PD universal fast charger or a 5A PPS output charger, using a 5A E-marker cable can reach 5A current. However, some private protocols encrypt the communication content. In this case, only the original charging cable can be purchased.

    Q5: Does the lightning wire have to be 5A current?
    A5: Yes, Thunderbolt 3, Thunderbolt 4, and USB 4 cables are all 5A current

    Q6: What current cable is USB C to lighting?
    A6: USB C to lighting is an encrypted cable. Although the terminal head has a built-in communication chip, the material specification and manufacturing process are both the current upper limit of 3A. At present, the highest charging power of USB C to lighting device is ipad pro up to 33W (15V 2.2A), and the specification of Iphone 13 pro Max is 27W, 9V3A

    Q7: Is the data transmission speed of 3A cable 5A cable directly related?
    A7: Data transfer performance is separate from power transfer performance and is not directly related. There is a 3A 10GBPS cable and a 5A 480Mbps cable.

    In conclusion, this issue will share with you what are the specific differences between 3A cable and 5A cable? They differ in manufacturing process, material specifications, selling price and so on. 5A cable can get a better fast charging experience. If there is no special requirement for charging, 3A cable is also possible.
    The above is the relevant content about 3A Cable and 5A cable. Welcome to follow or reply to discuss more questions.

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