Inductors (Coils)

Tech Notes

Automotive communication interface: Products recommended for PoC use (PoC filter inductors, chip beads)

The demand for high-speed automotive onboard interfaces is increasing, with a view towards supporting driving safety, reducing the environmental load, and improving comfort. For bidirectional communication, the automotive Ethernet format is commonly used, while LVDS is the choice for one-way communication. With LVDS (Low Voltage Differential Signaling), the preferred approach is to also adopt the PoC (Power over Coax) method that enables transmission of the signal and power supply over a single coaxial cable, thereby reducing the weight of wire harnesses in the car. This page describes usage examples and effects of inductors and chip beads specifically recommended for PoC filter applications.

Transfer system suitable for high-speed automotive interfaces

With the increasing speed and sophistication of interfaces in cars, the PoC (Power over Coax) approach is gaining in popularity, as it allows superimposing signals and power in one coaxial cable. TDK offers purpose-designed inductors for PoC filters which make it possible to achieve the required transfer characteristics while saving space.
PoC configurations make use of multi-inductance combinations to maintain high impedance over a broad frequency range, in order to separate the signal from the power supply.

Figure 1 PoC transfer system
PoC transfer system

High-speed and power ratings for LVDS-PoC

Sensing systems including cameras, radar and similar are evolving towards higher precision, which means that the amount of information which has to be handled increases, along with higher performance and functional complexity. Modules used for such systems therefore need to support high transfer speeds and high power ratings. Consequently, the PoC communication interface specifications are also shifting from 1.5Gbps to speeds in the 5Gbps range, and required power ratings are increasing from about 1W to about 5W.

Figure 2 Camera module for Autonomous-Driving / ADAS
Camera module for Autonomous-Driving / ADAS

Development of inductor (coil) optimized for PoC filter use

Realizing smaller dimensions (37% mounting footprint reduction)

Automotive camera modules and similar systems often are subject to severe space limitations, making compact product dimensions and smaller mounting footprints an important requirement.
A typical inductor configuration includes a four-piece combination of inductors and chip beads, but using the PoC purpose-designed inductors from TDK makes it possible to fulfill the same conditions with only one inductor and two chip beads.
This results in a mounting footprint reduction of about 37%.
When the number of inductors is reduced, it is necessary to select the components so that high impedance characteristics can be maintained over a broad frequency range.
At the same time, performance must be maintained and operation must be guaranteed up to high temperatures with a maximum of 150°C.

Figure 3 PoC filter configuration example
PoC filter configuration example
Table 1 TDK inductors recommended for PoC filter use

Example: 4Gbps 300mA PoC filter

Component Filter 1 Filter 2 Filter 3 Filter 4 Rdc[Ω] Mounting footprint
[mm²]
Recommended by TDK ADL3225VT-100M-TL000 / 1.2kΩ Chip Beads
MPZ1608S102ATD25
Chip Beads
MMZ1608Y152BTD25
N/A 1.05-44% 15.83-32%
General power supply circuit inductors NLCV32T-100K-EFRD/2kΩ NLCV25T-4R7M-EFRD/2kΩ Chip Beads
MPZ1608S102ATD25
Chip Beads
MMZ1608Y152BTD25
2.09 24.95

Maintaining required impedance characteristics over a wide range

Using PoC filter inductors of the ADL series makes it possible to maintain suitable impedance characteristics over a wide range.
Support for high current ratings is usually implemented by using multiple inductors, but selecting PoC filter inductors of the ADL series enables realizing the same goal with fewer components.
Compared to the use of conventional inductors, frequency ripples are reduced over a wide range.
In this way, TDK solutions help to realize flat frequency characteristics.

Figure 4 Effect of TDK inductors for PoC filter use
Effect of TDK inductors for PoC filter use

List of TDK inductors recommended for PoC filter use

As shown in Fig. 5, a configuration with TDK PoC inductors comprises "Filter 1" and "Filter 2". If the required PoC filter specifications can be realized with "Filter 1", chip beads or similar are used for "Filter 2".
TDK offers a lineup of various PoC filter inductors for different current ratings and filter requirements (Table 2).
The ADL3225V, ADL3225VT, ADM32FSC and ADM45FDC- series products are designed for wide-band applications. The ADL2012 series and the MDF1005GAD series (under development) are inductors for realizing a more compact "Filter 2".
The lineup also comprises the high-current type ADL3225VM and ADM32FSC series.

Figure 5 Types of inductors for PoC filter use
Types of inductors for PoC filter use
Table 2 TDK inductors for PoC filter use

Note: *** stands for the inductance value or impedance value.For details, please see the respective product specifications.

PoC
current rating
item# Inductance (example) Recommended inductor Product features Status Specifications
[μH] Tolerance [%] Filter 1 Filter 2
Filter 3
300mA ADL3225VT-100M-TL000 10 20   Wide-band support Mass production Product details
300mA ADL3225V-470MT-TL000 47 20   Mass production Product details
~700mA ADL2012-***M 1.5 20   Compact size / Wide-band support Under development (Contact us)
~700mA ADL3225VT-4R7M-TL000 4.7 20   Wide-band support Mass production Product details
~1,000mA ADL3225VM-***M-TL000 10 20 Medium power / Wide-band support for Filter 1 Under development (Contact us)
High power / Wide-band support for Filter 2 Under development (Contact us)
~700mA ADM32FSC-***M 22 20   High power Under development (Contact us)
~1000mA ADM45FDC-***M 10 20   High power Under development (Contact us)
560mA MDF1005GAD-***
ATD69
(GHz band noise suppressor)   Compact size / High frequency band support Under development (Contact us)

For specific inductance value requirements, please contact us.