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Difference between USB-C 3A cable and eMark-5A cable

E-Mark is short for Electronically Marked. It actually is a protocol controller, which includes the power supply, power receiving, and power transmitting capabilities of the product (sink, source, cable), and the corresponding protocol and transmission requirements, which generally require PD (power deliver) or PPS (Programmable Power Supply) products. 

In the USB-C PD (Power Delivery) protocol, the maximum charging power is specified as 100W, which are 5V/ 3A, 9V/3A, 12V/3A, 15V/3A, 20V/5A. If the electric current is equal to or less than a 3A wire, then using a 3A wire will be just fine. If the electric current is greater than 3A, it must use a 5A wire with an E-Mark chip. The wire’s capability level of the electric current depends on the thickness of the wire.  

Why do we need this?

It is in fact a safe protection mechanism. For example, the charging power of the Apple MacBook Pro 15’’ is 87W, which is 20V / 4.35A. When the E-Mark chip and 3A wire are inserted, the charger will only output the maximum electric current of 20V / 3A because it does not recognize the E-Market chip protocol. If there is no such mechanism when using Apple’s 87W charger with a maximum of 60W, the charger may output 87W (20V / 4.35A). It‘s possible for bugs to appear in the PD communication protocol, and the wire itself only has a 3A load capacity. This would cause the wires to burn out or terminate the equipment. 

The same method can be applied to the Samsung Note 10+ or S20 Ultra supports 45W fast charging. In fact, the maximum electrical current is 4A, therefore it also requires a 5A cable with E-Mark.

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comments ( 1 )

Feb 23, 2021

I find this a little confusing between 3a and 5a. If I have a battery pack that can charge at 100 watts then a 5a cable makes sense with the e-mark (from what you folks say). How about an iPad Pro 2020? I gather a Samsung Galaxy s10+ should go with a 3a?

Is there a disadvantage using a 5a with the Galaxy s10+ rather than the 3a?

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