With the rapid development of automotive electronics, in order to ensure safety, the importance of noise suppression measures has become increasingly prominent. Affected by environmental regulations, low fuel consumption and driver assistance systems are constantly evolving. The number of Electronic Control Units (hereinafter ECUs) per vehicle is increasing, and the Internet of Vehicles is constantly requiring high speed. These cables of the in-vehicle LAN connected to the ECU are prone to interference electric waves and are susceptible to external noise, so noise suppression measures are indispensable. In order to adapt to this trend, Murata Manufacturing Co., Ltd. (hereinafter referred to as "Murata") is constantly working on the development of common mode choke coils (hereinafter referred to as CMCC) with excellent noise suppression and high reliability. CMCC is a product that uses the difference between mode propagation characteristics to suppress common mode noise. Murata has developed the CMCC for vehicles by making full use of the existing magnetic material technology, magnetic circuit design technology and unique winding technology accumulated in the CMCC for the people's livelihood. Figure 1. Example of a noise countermeasure for BroadR-Reach® In addition to ordinary cars, considering the car Ethernet installed on trucks and buses, the transmission cable length must be set to 15m. In addition, in order to increase the transmission speed of the uncompressed image transmission of the in-vehicle camera and to minimize the frequency of retransmission due to transmission errors, the response speed is increased and standardized. Although the return loss (Sdd11) and insertion loss (Sdd21) on the currently popular CMCC have met the specification limit, they do not satisfy the balance (Sds21), which may cause a drop in transmission quality. Figure 2. Transmission specifications for automotive Ethernet and the characteristics of popular CMCC In terms of the popularization of CMCC for Minsheng Ethernet, it is not very clear about the Ethernet transmission specifications. (Dash line: specification limit value; solid line: CMCC-DLW21SN491XQ for people's livelihood) Compared with the general equipment specifications (CISPR22), the strict automotive noise specification (CISPR25) is not only suitable for Ethernet, but also suitable for vehicles with a large number of ECUs and information equipment in a narrow space. Special attention should be paid here to the effects of electromagnetic waves generated by radio waves (AM, FM, TV) and communication devices (GPS, 4G-LTE, etc.). Figure 3: Comparison of noise limits for vehicle and live equipment (radiation noise) ※Because of the different measurement conditions, it is not possible to make a simple comparison. The limit value itself is more serious. The measurement distance is also shorter than the 1 m of the vehicle (CISPR25) and 3 meters of the CICR22. The CMCC specification for the in-vehicle Ethernet specifies the limit value of the squelch characteristic (Scc21). Considering the noise specifications for automobiles, it is not satisfactory to use the popular CMCC for Minsheng Ethernet. Therefore, from the perspective of both transmission characteristics and squelch characteristics, it is necessary to use a higher-performance dedicated CMCC to solve the EMC problem. Figure 4. Vehicle Ethernet squelch characteristics specifications and popular CMCC features In terms of the popular CMCC for Minsheng Ethernet, the Ethernet squelch characteristic specification is not well understood. (Dash line: standard limit value, solid line: CMCC-DLW21SN491XQ for people's livelihood) Murata's newly launched DLW43MH series is a CMCC for BroadR-Reach® that meets the automotive Ethernet standard and is the most popular. It achieves high insertion loss characteristics and small mode conversion characteristics through Murata's unique ferrite material technology and high-level winding technology, so it can achieve good noise suppression and high immunity performance that meets the vehicle Ethernet standard. Figure 5. Automotive Ethernet Specification Limits and DLW43MH Features The figure below shows the specific circuit using the DLW43MH, and sometimes it is also used with the LC filter. Figure 6. Example of Ethernet use of the car camera Figure 7. Use case of Gateway BroadR-Reach® includes OBD (On-Board DiagnosTIcs), on-board camera systems, infotainment devices and gateways to connect them, as well as powertrains and safety devices, which are essential for autopilot The possibility of development. Murata is constantly striving for the development of CMCC products for automotive Ethernet that meet the requirements of noise suppression, such as miniaturization, high-temperature adaptation, high-speed transmission, high reliability, etc., and will continue to expand the lineup of other magnetic components. PCBA BOM,Iron Lithium Battery Board,PCBA Manufacturer,Battery Charger Circuit Board,LDJ PCB Huizhou Liandajin Electronic Co., Ltd , https://www.ldjcircuitboard.com
