Common mode chokes that meet the 10BASE-T1S specification

As the development of a new generation of vehicles with the goal of autonomous driving is booming, vehicle architectures are beginning to change dramatically. Among them, connecting the in-vehicle network between the ECUs responsible for advanced driver assistance systems (ADAS) is becoming an important factor.

In in-vehicle networks, automotive Ethernet is particularly of interest, with 100BASE-T1 (100Mbps) and 1000BASE-T1 (1Gbps) being installed in sensor systems such as cameras, radars, and lidars. In addition, the new standard for automotive Ethernet, 10BASE-T1S with a data rate of 10 Mbps, is attracting increasing attention.

Application examples: Applications that may include actuator systems or sensors.

10BASE-T1S summarize

10BASE-T1S is one of the latest IEEE standards for automotive Ethernet, developed as the IEEE 802.3cg standard, and uses a pair of unshielded twinax cables such as UTP for communication. Unlike 1-to-1 point-to-point connections (Figure 1), which are built through networks such as 100BASE-T1 and 1000BASE-T1 switches, 10BASE-T1S uses switchless multipoint connections (Figure 2) to reduce costs. As a result, even as electronic systems become more advanced and networks continue to increase in number and complexity, more flexible and faster architectures can be built.

Figure1.   100BASE-T1 , 1000BASE-T1 (point-to-point connection

Figure2. 10BASE-T1S (Multipoint Connection)

10BASE-T1S compliant products (common mode chokes/filters)

Since the 10BASE-T1S uses a switchless multipoint connection, when multiple ECUs are connected to a single line, the radiation caused by the length of the wiring harness and branches, and the capacitance composition of the ECU increase, which is prone to ringing caused by communication waveforms. Therefore, common-mode chokes for EMC need to minimize stray capacitance between lines and have good mode conversion characteristics (Sds21, Sds12, Ssd21, Ssd12). As a result, EASTEVER's common-mode choke coils are designed to meet the 10BASE-T1S specification due to their excellent design in terms of line-to-line stray capacitance and mode conversion characteristics.


Common mode choke coefficient

μH (typical from) @100kHz

Parasitic capacitance  pF (maximum)

DC resistance  Ω (max)

Current rating mA (max)

ECT1210-2410-H087 240
10 4.1 70

Table 1: Common Mode Chokes/Filters Compliant with the 10BASE-T1 Specification

S parameter

In general, the mode conversion characteristics (SDC11, SSD21, SSD12), return loss (SDD11), and insertion loss (SDD21) are required in the selection and ECU design of automotive Ethernet components.  These S-parameters are specified in the standard in IEEE802.3cg (Sdd11, Sdc11). In addition, the OPEN Alliance is actively developing these standards.  Therefore, the S-parameters of individual components as well as the S-parameters of combined components are important indicators for the design of ECUs.  The following are the S-parameters (typical values) for common mode chokes and varistors.   

Schema shifts

Differential communication signals are usually transmitted in the conduction mode of differential mode, while noise is transmitted in the conduction mode of common mode. In some cases, depending on the electronic components used in the differential communication line, the transmission mode may be converted from differential mode to common mode, or from common mode to differential mode Through the conversion of conduction modes (mode conversion), the conversion of a differential signal to noise, or the conversion of noise to a differential signal, the result is a reduction in the noise resistance of the ECU itself, causing the ECU to malfunction or the ECU itself to produce noise The influence of these electronic components is generally caused by the asymmetry of the differential communication line, which is the differential characteristics of inductance and electrostatic capacitance as shown in Figure 4,7 and 8. The products introduced in this paper have excellent mode conversion characteristics

An example of a common-mode choke and chip varistor in a daisy-chain connection

Figure 7: 10BASE-T1S (Multipoint Connection)

IEEE802.3 Physical Layer Standards

IEEE802.3cg 10Mbps Single Pair Ethernet specification, 10BASE-T1S has developed 10Mbps operationally related and physical layer specifications and management parameters for power delivery.

Discussions are currently underway to develop a physical layer specification to extend cable lengths, add nodes for the 10 Mbps single-to-multipoint segment of IEEE802.3DA, and enhance the development of control parameters.

Topological structure

10BASE-T1 100BASE-T1 1000BASE-T1 Multi-Gig BASE-T1


IEEE80.3cg IEEE802.3bw IEEE802.3bp IEEE802.3ch
Data Rate 10Mbps 100Mbps 1Gbps 2.5/5/10Gbps
Code 4B/5B (DME)*2 PAM3 PAM3 PAM4
Methods of Communication Half-duplex communication          Full Duplex Communication Full Duplex Communication Full Duplex Communication Full Duplex Communication
Topological Structure Point to Point/ Multi-point Point to Point Point to Point Point to Point

*2: DME: Differential Manchester encoding


In next-generation vehicles aimed at autonomous driving, there is a lot of interest in in-vehicle networks that connect ECUs and devices. Automotive Ethernet has standards for different data rates. TDK offers a wide range of common mode chokes and chip varistors that comply with various standards. Our ACT1210E-241-2P products are optimized for 10Base-T1 with a transfer speed of 10 Mbps and set a new benchmark for components in automotive Ethernet applications.



James  Wang

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Helen   Xie

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Karmen  Wu

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