Power Over Coax (PoC) Inductors for Automotive Applications

Murata's LQW series AEC-Q200-rated automotive inductors for the PoC Bias-T circuit offer broad band impedance, high rated current, good saturation, and a temperature range of -40°C to +125°C with EIA sizes of 1812, 1210, and 0805 available.

PoC is often used for SerDes interfaces where the serializer and deserializer are connected by a coaxial cable. High-frequency signal and DC power are superimposed on this coaxial cable.

When this is the case, a Bias-T circuit is added to prevent high-frequency signals from leaking into the power line and DC current from entering the deserializer.

With Bias-T circuits, capacitors that pass high-frequency signals while blocking DC current are used along with coils that pass DC current while blocking high-frequency signals.

The purpose of a Bias-T inductor is to block AC and allow DC to pass, so the inductor must have high-impedance characteristics. If the impedance is too low, AC signal components may leak into the power line and signal components transmitted over the coaxial cable may be attenuated. Murata offers the LQW series inductors which are suitable for the Bias-T filtering function previously described.