A Tiny Inductor Helps Separate Power and Data on Automotive Coax
An automotive camera can need a high-speed data path and a stable supply at the same time. Running separate cables for each function adds harness mass, connectors, routing effort, and potential failure points. Power-over-coax (PoC) combines the two onto one coaxial cable, but the simplification moves a difficult task into the electrical interface: the system must pass data while delivering DC power, then separate them cleanly before the signal reaches the camera electronics.
A component update aimed at the PoC filter
TDK has expanded the MLJ1608-G multilayer-inductor series for automotive PoC circuits. The new parts use a 1608 metric footprint, approximately 1.6 by 0.8 by 0.8 mm, and the company reports mass production beginning in October 2026. The series is designed to provide high impedance across 300 MHz to 2 GHz. The reported inductance is 1.2 μH, compared with 0.56 μH for the conventional components used as the comparison point.
At 100 MHz to 700 MHz, the new component is described as providing 1.7 to 2 times higher impedance than those conventional parts. That comparison is frequency-dependent: an inductor is not an ideal lumped value across all frequencies. Parasitic capacitance, winding resistance, core behavior, mounting geometry, and the surrounding circuit determine its impedance curve. The product is AEC-Q200 compliant, a qualification relevant to automotive passive-component reliability, but designers still need to validate the complete filter in their own layout.
Why one cable creates a filtering problem
PoC places DC power and a broadband data signal on the same coaxial conductor. At the camera end, the power must be routed to the supply input while the data is directed to the receiver; at the ECU end, the functions must be combined without degrading the signal. A wideband filter network uses multiple inductors and other components to distinguish the low-frequency power path from the high-frequency communication path.
In this network, high impedance at the data frequencies helps keep the signal from escaping into the power branch. The exact requirement is not simply “more inductance.” The filter must maintain adequate attenuation where the system needs isolation, while keeping insertion loss, return loss, and signal integrity within the camera link’s operating budget. Component selection is therefore based on the impedance-versus-frequency curve and the assembled network, not just the nominal μH value.
Multilayer construction and size trade-offs
A multilayer structure can place a useful magnetic element in a small surface-mount footprint. That matters around camera modules, where the connector, sensor, serializer, power circuitry, mechanical mount, and thermal path compete for space. Smaller filtering components may allow a more compact module or a less congested printed-circuit board, but miniaturization does not eliminate constraints on current handling, DC resistance, temperature rise, and mechanical robustness.
The design team should check the inductor’s rated current and saturation behavior under the actual DC load. If the DC component is large, the effective inductance can change and reduce the intended isolation. Copper loss also creates heat, while temperature changes can shift component behavior. A filter that looks acceptable in a small-signal simulation may not behave identically when the camera supply is loaded, the cable is at its longest, or the board is exposed to a wide temperature range.
High-frequency behavior must be validated in the system
The stated frequency span reaches 2 GHz, where parasitic effects are no longer minor details. Pad dimensions, ground return paths, component spacing, coax transitions, and the geometry of adjacent traces can all alter the measured response. A schematic-level model is useful for initial design, but the final filter should be checked using a layout-aware simulation and measurements on representative hardware.
Automotive camera links also face electromagnetic compatibility demands. The filter must prevent conducted noise from coupling between the power rail and the data channel, yet should not create resonances that amplify interference. Engineers should test emissions and immunity across supply transients and operating states, including camera startup and changing data traffic. The inductor is only one part of that result; capacitors, common-mode behavior, cable termination, and grounding are equally important.
Qualification is a baseline, not a finished design
AEC-Q200 compliance provides a useful qualification baseline for passive components exposed to automotive environments. It does not certify every finished camera module or guarantee performance in every cable architecture. The design still must consider vibration, thermal cycling, humidity, solder-joint strain, and the temperature profile inside the camera housing. The mechanical placement of a small component near a connector or board edge can matter as much as its electrical characteristics.
For a production program, engineers should test the exact package and land pattern, review assembly tolerances, and confirm that reflow conditions match component guidance. PoC networks can be sensitive to small shifts in impedance, so it is prudent to evaluate more than one board lot and to include worst-case component tolerances in the channel budget. Qualification evidence and system-level validation answer different questions; both are needed.
Procurement and platform implications
Moving from a two-cable arrangement to PoC can reduce wiring complexity and vehicle harness content, but it concentrates more functions in one signal path. That makes the filter a platform-level design choice rather than an interchangeable afterthought. A sourcing alternate needs a comparable impedance curve over the relevant band, acceptable current and temperature performance, equivalent qualification status, and a footprint that does not disturb the tuned network.
Procurement teams should align the approved part number with the exact camera architecture and keep alternate approvals tied to electrical measurements. A part that matches nominal inductance but differs in self-resonance or parasitic capacitance may shift the filter response. Second sourcing is still valuable, particularly for long automotive programs, but the validation plan should include the actual cable, connector, serializer, and receiver combination.
Conclusion
The MLJ1608-G expansion addresses a specific PoC bottleneck: preserving separation between high-frequency camera data and DC power in a compact automotive design. Higher impedance over a broad band can give engineers more room to shape the filter, but only a complete link evaluation can show whether that room translates into robust signal quality. The useful lesson is that cable reduction does not remove complexity; it relocates complexity into the components and interfaces that make the shared cable work.
Related Listed Companies to Watch
Directly Related Companies
| Company | Ticker | Market | Relation | Strength |
|---|---|---|---|---|
| TDK | 6762.T / TTDKY | TSE / OTC | Passive-component manufacturer; the specific MLJ1608-G product is the subject of this development | High |
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