6 28, 2022
Introduction: With the introduction of PD3.1, USB4Gen3, Thunderbolt 4 and other standards, high-power current transmission, ultra-high-speed data transmission, video signal transmission has entered a rapid development stage. And the cable as a key bridge to transmit current, data, video signals, but also facing high standards under the market for its new requirements, "one cable with two eMarkers" began to appear frequently in the market.
What is "one cable with two eMarkers" ?
USB Type-C cables have two interfaces, front and back, and when both ends of the cable are embedded with an eMarker, we commonly call it "one cable with two eMarkers".
The full name of the eMarker is "Electronically Marked Cable", also known as the USB electronic tag chip, which can be understood as the electronic identity tag of the USB Type-C cable. Through the eMarker can read the various attributes of the cable, including power transmission capacity, data transmission capacity, video transmission capacity and ID and other information. In this way, the output (e.g., charging head, notebook) can be adjusted to match the voltage/current or audio/video signal according to the device connected to the output (e.g., cell phone or monitor). eMarker's popularity is also inseparable from the requirements of the USB-IF Association, which stipulates that cables that want to support 5A high current, USB 3.0 and higher transmission speed, and video transmission capabilities need eMarkers.
The advantages of "one cable with two eMarkers"
1、More accurate PD communication information
The eMarker can read various properties of the USB Type-C cable, and the eMarker needs to match the PD communication information at both ends of the cable and broadcast it.
In this regard, we conducted a comparison test between the "one-wire, two-core" cable and the single eMarker cable with load, and found that the PD communication information of the "one-wire, two-core" cable is more accurate. Especially in the case of large load and transient, the PD communication of both cables will be more affected and the difference is more obvious.
The comparison test results are as follows
From the above figure, we can find that there is a slight difference in the PD communication information of the single eMarker cable. The part marked by the red arrow in the figure shows that there is a potential difference in its BMC code stream. The longer the cable length, the more pronounced this difference is. Comparing the waveform of the "one wire, two core" cable under load, we can see that it is exactly on the same level as the BMC stream of the PD Source, which means that the information is accurately transmitted.
By capturing the packets, we can better detect the resulting differences. Below is the packet content of the single eMarker cable.
▲ Single eMarker cable: Discldentity (communication message from power supply)
▲ Single eMarker cable: GoodCRC information from eMarker replies
▲ Single eMarker cable: eMarker replies to DiscldentityACK's messages
▲ Single eMarker cable: Power replies to GoodCRC messages
The following are the data packages of the "one cable with two eMarkers" cable.
▲"one cable with two eMarkers" cable: Discldentity (communication message from power supply)
▲"one cable with two eMarkers" cable: GoodCRC information from eMarker replies
▲ "one cable with two eMarkers" cable: eMarker replies to DiscldentityACK's messages
▲ "one cable with two eMarkers" cable: Power replies to GoodCRC messages
2、With less wire, cables can be made thinner, longer and softer while reducing wire costs
Comparing the number of wires inside the "one wire, two core" cable and the single eMarker cable, we can see that the "one wire, two core" cable has 5 wires inside and the single eMarker cable has 6 wires inside. With more than one eMarker, the cost of wire can be reduced and the cable can be designed to be thinner, softer and more beautiful. A well-known cell phone brand, through the "one-wire, two-core" technology, the cable diameter reduced from 4.2mm to 3.65mm.
USB Type-C cables must be considered for high power fast charging when the temperature issue, over-temperature protection is particularly necessary. The upcoming eMarker HUSB332C from Wisersoft Semiconductor has an integrated over-temperature protection function that eliminates the need to design over-temperature protection circuits when embedded in both ends of the cable, replacing the traditional PTC over-temperature protection method and reducing the number of peripheral devices and costs.
In actual use, current flows through both ends of the cable at the same time, and only one end of the cable with eMarker embedded cannot perform its over-temperature protection function. The eMarker's high performance can only be fully demonstrated through the "one-wire, two-core" technology.
Conclusion: According to the market trend - high power fast charging + ultra-high speed transmission, eMarker is gradually becoming the standard for USB Type-C cables. In order to reduce the cable cost, improve the accuracy of PD communication information transmission, and improve the performance of the cable, "one cable with two eMarkers" has become an urgent need.