Introduction: With the launch of PD3.1, USB4Gen3, Thunder 4 and other standards, high-power current transmission, ultra-high speed data transmission, video signal transmission into the rapid development stage. As a key bridge for the transmission of current, data and video signals, cables are also facing the new requirements put forward by the market under the high standard. "one-line dual-core" cables begin to appear frequently in the market.
What is "one line two core"?
A USB Type-C cable has two ports, front and back, and when an eMarker is embedded in each end of the cable, we colloquially call it a "one-wire, two-core" cable.
eMarker's full name is "Electronically Marked Cable," also known as the USB electronic tag chip, which can be interpreted as the electronic identity tag for USB Type-C cables. Various attributes of the cable can be read through eMarker, including power transmission capacity, data transmission capacity, video transmission capacity, ID and other information. In this way, the output (e.g., charging head, laptop) can adjust the matching voltage/current or audio/video signal according to the device that the output is connected to (e.g., mobile phone or monitor). The popularity of eMarker is also related to the requirements of the USB-IF Association. USB-IF stipulates that the cable must carry eMarker if it wants to support 5A high current, USB3.0 and above transmission speed, and video transmission function.
The advantage of "one line and two cores"
1. PD communication information is more accurate
Various attributes of USB Type-C cable can be read by eMarker. eMarker needs to match PD communication information at both ends of the cable and broadcast it out. After PD communication information is transmitted to both ends of the cable with a certain length, will its accuracy rate change?
To this end, we conducted a load comparison test between the "one-line dual-core" cable and the single eMarker cable. Through the comparison test, we found that the PD communication information of the "one-line dual-core" cable was more accurate. Especially in the case of large load and transient, PD communication of the two kinds of cables will be more affected, and the difference is more obvious.
The comparative test results are shown below
As can be seen from the figure above, PD communication information of a single eMarker cable is slightly different. The part marked by the red arrow in the figure shows that there is a potential difference in its BMC code stream. Specifically, eMarker information generates an upbiased voltage range due to the length of the cable, and the waveform also generates an upbiased displacement. The difference is more obvious when the cable length is longer. By comparing the waveform of the "one-line dual-core" cable with the load, it can be seen that it is completely at the same level as the BMC code stream of PD Source, indicating that information is accurately transmitted.
By grabbing the packets, we can better spot the resulting differences. Below is the packet content for a single eMarker cable.
▲ Single eMarker cable: Discldentity (communication information from power supply)
▲ Single eMarker cable: GoodCRC information replied by eMarker
▲ Single eMarker cable: eMarker replies messages to DiscldentityACK
▲ Single eMarker cable: Power return GoodCRC information
The following is the data packet content of the one-wire dual-core cable.
▲ "One-line Dual-core" cable: Discldentity (communication information issued by the power supply)
▲ "One-line Dual-core" cable: GoodCRC information replied by eMarker
▲ “一线双芯”线缆：eMarker回复DiscldentityACK的信息
▲ "One-line dual-core" cable: The power supply returns GoodCRC information
2, less wire consumption, the cable can be made thinner, longer and softer at the same time reduce the cost of wire
Comparing the number of internal wires in a "one-line dual-core" cable and a single eMarker cable, we can see that a "one-line dual-core" cable has five internal wires and a single eMarker cable has six internal wires. With one more eMarker, the wire cost can be reduced, and the cable can also be designed thinner, softer and more beautiful. A well-known mobile phone brand has reduced the cable diameter from 4.2mm to 3.65mm by using the "one line, two cores" technology.
3. Higher performance -- take full advantage of eMarker's overtemperature protection
The temperature of USB Type-C cable must be considered during high-power fast charging. The overtemperature protection function is especially necessary. The eMarker HUSB332C, to be launched by Inenttech Semiconductor, integrates the function of overtemperature protection, which can avoid the design of overtemperature protection circuit when embedded at both ends of the cable, replacing the traditional PTC overtemperature protection, reducing the number of peripheral devices and reducing the cost.
In practice, the current flows through both ends of the cable at the same time, and a cable with eMarker embedded in one end will not be able to provide over-temperature protection. The "one line, two core" technology is the only way to fully showcase eMarker's high performance.
Summary: According to the development trend of the market -- high-power fast charge + ultra-high speed transmission, eMarker has gradually become the standard USB Type-C cable. In order to reduce the cable cost, improve the accuracy of PD communication information transmission, and improve the performance of the cable qualitatively, "one-line dual-core" has become a requirement.
