DLW43MH201XK2
Noise suppression technologies/case study introduction (Automotive)
An Introduction to Noise Suppression in Onboard Ethernet 100Base-T1 (1)
INDEX
1. What is Onboard Ethernet?
Onboard Ethernet:"Communication systems used in automobiles"
Various interface standards are used in automobiles, depending on the application.
Table 1: Communication systems used in automobiles
| Communication system | Speed | Applications, features |
|---|---|---|
| CAN/LIN | 33k/125k/250k/500kbps | Onboard LAN standard adopted for general ECUs |
| FlexRay | 2M/5M/10Mbps | Used in the powertrain, chassis, and other control systems |
| MOST | 25M/50M/150Mbps | Adopted for use in onboard audio multimedia systems |
| Ethernet | 100M/1Gbps | PC LAN standard, also used in diagnostics 100BASE-TX, 100Base-T1 |
Table 2: Onboard Ethernet standards
| Standard | Transmission speed | Number of pairs | Notes |
|---|---|---|---|
| 100Base-T1 | 100Mbps | 1 pair | Supports full-duplex communication at 100 Mbps with 1 pair. Standardized by OPEN Alliance. |
| 100Base-TX | 100Mbps | 2 pairs | Based on the existing 100Base-TX and used to improve onboard EMC performance. |
| RTPGE (1000Base-T1) | 1000Mbps | 1 or 2 pairs | Being reviewed for standardization by IEEE. The standard reduced the amount of wiring in the existing 1000Base-T for vehicle and industrial device applications. |
2. Necessity of Noise Suppression in Onboard Ethernet
1.Differential transmission noise
In differential transmissions including Ethernet, noise occurs due to a common mode current caused by various factors.
2.Ethernet problems
The cables used for Ethernet are different from USB and HDMI cables.
3.Noise standards of onboard devices
Onboard devices have a shorter antenna distance and stricter limit values than consumer products.
Recommended!
A common mode choke coil is an effective way to suppress noise in a differential transmission.
- The reverse phase (differential mode) signal is canceled by the magnetic field → penetrates
- The magnetic field superimposes the in-phase (common mode) noise → reflects
You can selectively drop just the common mode!
We recommend the DLW43MH series as the optimal common mode choke coil for 100Base-T1 noise suppression.
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