Automotive Ethernet is rapidly moving from infotainment into safety‑critical control networks, and passive components now have to meet stricter signal integrity and reliability requirements.
Murata’s DLW32MH241MX2 is a 1210 size metal‑terminal common mode choke coil designed specifically to meet the OPEN Alliance 10Base‑T1S in‑vehicle Ethernet specifications, giving hardware designers a qualified drop‑in option for new automotive interfaces.
Key features and benefits
- Dedicated 10Base‑T1S compliance
The DLW32MH241MX2 is engineered to satisfy Scc21: Class3 (240 µH) and Cp: Class3 (≤ 10 pF) requirements defined by the OPEN Alliance 10Base‑T1S in‑vehicle Ethernet standard, so designers can focus on system‑level validation instead of choke coil qualification according to manufacturer datasheet. - Automotive‑grade robustness
The component is AEC‑Q200 compliant, indicating that it has passed automotive stress tests for thermal cycling, mechanical shock, vibration, and humidity according to manufacturer datasheet. This makes it suitable for deployment in ECUs exposed to harsh under‑hood and chassis environments. - Compact 1210 footprint with metal terminals
With a 3.2 × 2.5 mm footprint, the choke fits the 1210 inch size class and uses metal terminal technology to improve mechanical strength and solder joint reliability. Metal terminals help absorb board flex and thermal stress, reducing the risk of micro‑cracks or solder fatigue in long‑life automotive designs. - Wide operating temperature range
The specified operating temperature range of −40 to 125 °C aligns with typical automotive component classes according to manufacturer datasheet. This supports placement close to heat‑generating ICs and in engine compartment environments. - Optimized for low‑speed single‑pair Ethernet
The nominal common mode inductance of 240 µH at 0.1 MHz with a tolerance of −20%/+50% is tuned for common‑mode noise suppression on 10 Mbps single‑pair Ethernet lines. This helps maintain signal integrity over cable harnesses without excessive insertion loss in the differential signal band.
Main specifications overview
| Parameter | Value / classification |
|---|---|
| Product number | DLW32MH241MX2 |
| Size class | 1210 inch (3.2 × 2.5 mm) |
| Common mode inductance | 240 µH (−20% / +50%) at 0.1 MHz |
| Rated voltage | 80 V |
| Rated current | 70 mA |
| Operating temperature | −40 to 125 °C |
| Automotive qualification | AEC‑Q200 compliant |
| Target standard | 10Base‑T1S, Scc21: Class3, Cp: Class3 |
Typical applications
The DLW32MH241MX2 is targeted at signal‑line common mode noise suppression in automotive Ethernet networks, specifically where 10Base‑T1S single‑pair links are used.
- Domain and zone controllers
Central vehicle computers and gateway ECUs that aggregate data from multiple sensors and actuators can use 10Base‑T1S for deterministic, low‑speed control traffic. The choke coil sits close to the Ethernet PHY, suppressing common‑mode noise injected onto harnesses. - Sensor and actuator nodes
Smart sensors (e.g. radar modules with low‑rate configuration channels), motor drivers, and other distributed nodes can use 10Base‑T1S to simplify cabling. The component helps ensure EMC compliance when cables run near high‑current wiring or switching power stages. - Body and comfort systems
Door modules, seat controllers, HVAC units, and lighting controllers increasingly rely on networked communication instead of standalone CAN segments. A dedicated 10Base‑T1S choke simplifies EMC design when migrating these subsystems to Ethernet‑based architectures. - Transition from CAN to Ethernet
As OEMs move from legacy CAN bus to Ethernet for control interfaces, mixed networks and adapter modules must maintain compatibility and meet EMC standards. Using a choke coil validated for 10Base‑T1S reduces integration risk when introducing Ethernet into existing harness topologies.
In practice, the choke will be placed either in front of or behind the Ethernet PHY on each twisted pair, typically in series with the line, forming part of the common‑mode filter network together with surge protection and termination components.
Technical highlights
10Base‑T1S and OPEN Alliance requirements
10Base‑T1S is an in‑vehicle single‑pair Ethernet standard capable of 10 Mbps communication over a single twisted pair. It is designed for multi‑drop topologies and relatively short distances typical of automotive harnesses. The OPEN Alliance specification defines classes for common mode choke coils:
- Scc21: Class3 defines the required common mode inductance (240 µH) at a specific test frequency.
- Cp: Class3 defines the maximum parasitic capacitance (≤ 10 pF).
Meeting these values is critical: too little inductance reduces common‑mode attenuation, while too high parasitic capacitance can distort the differential signal and increase insertion loss or reflections at the operating frequency band.
Metal terminal structure
Murata integrates metal terminal technology into the DLW32MH241MX2. Compared with conventional chip inductors with exposed ceramic ends, metal terminals:
- Improve mechanical robustness by decoupling ceramic stress from PCB flex.
- Offer more consistent solder fillets and wetting, which is beneficial for automated optical inspection and reliability analysis.
- Help mitigate failures due to board warpage during reflow, especially on large automotive PCBs.
For designers, this means the choke can be placed in areas subject to mechanical stress (e.g. near board edges or mounting points) with lower risk of cracking.
Electrical ratings and derating considerations
- The rated voltage of 80 V is sufficient for typical automotive Ethernet applications, which operate well below this level in normal conditions but may see transient spikes.
- The rated current of 70 mA covers common 10Base‑T1S PHY implementations that operate at low line currents.
- The wide inductance tolerance (−20%/+50%) reflects the design trade‑off between meeting EMC targets and manufacturing dispersion; selection should be done with this spread in mind when simulating line behavior.
Although exact derating curves and frequency characteristics are not detailed in the press release, engineers should refer to the manufacturer datasheet for impedance vs. frequency plots, insertion loss, and common‑mode attenuation to finalize filter design.
Design‑in notes for engineers
- Follow 10Base‑T1S layout guidelines
Place the common mode choke as close as possible to the Ethernet PHY line pins, keeping the differential pair tightly coupled and length‑matched through the component. Avoid unnecessary vias and stubs around the choke to minimize impedance discontinuities. - Consider EMC at harness level
The choke’s primary role is to attenuate common‑mode noise that can radiate from vehicle wiring. Combine it with proper cable shielding, connector selection, and return path control to meet CISPR and OEM‑specific EMC requirements. - Account for inductance tolerance in simulations
Use the worst‑case range of 240 µH with −20%/+50% tolerance in signal integrity and EMC simulations. This helps ensure sufficient margin even when components are at tolerance extremes. - Verify thermal behavior in actual ECU
Although the component is specified up to 125 °C, local hot spots near power devices can push temperatures higher in practice. Include the common mode choke in thermal analysis and, if possible, measure its case temperature in prototype units. - Check compatibility with other Ethernet variants
While DLW32MH241MX2 is targeted at 10Base‑T1S, using it in other Ethernet PHY configurations (e.g. different single‑pair standards) should be evaluated against their specific choke requirements. The manufacturer’s recommended interface list is a useful starting point. - Plan for mechanical robustness and assembly
The metal terminal design helps with board flex and vibration, but overall ECU mechanical design (mounting points, enclosure stiffness) still matters. Align the component orientation with the main flex directions of the PCB and adhere to recommended land pattern dimensions from the datasheet.
Source
This article is based on information published in the manufacturer’s product and event news press release for the DLW32MH241MX2, complemented by the official product page and recommended interface documentation according to manufacturer datasheet and related materials.
