Schwarzbeck CDN USB-C Coupling Decoupling Network for IEC 61000-4-6

The Schwarzbeck CDN USB-C is part of the coupling decoupling network series for conducted common mode immunity testing according to IEC/EN 61000-4-6. The CDN S24 USB-C is compliant to IEC 61000-4-6 figure D.1 and is suitable for immunity testing on screened USB-C lines.

The CDN S24 USB-C is intended to measure EuTs with USB-C interface in the frequency range from 150 kHz to 230 MHz. The circuitry is shown in Fig. 3.

The USB-C standard allows connecting two devices via a single cable with two connectors. There are no additional connectors allowed and female-female adaptors disable the polarity sensing of the reversible USB-C connectors.

For this reason the AE connector is a fixed cable with a male plug.

Since the CDN USB-C needs to be connected directly to the calibration adapter the EuT connector cannot be a cable. The CDN USB-C is wired so that the USB-C polarity sensing still works correctly.

To ensure that the total loss is within USB limits it is important to use the shortest possible USB cable for EuT connection (20cm recommended)

All CDNs comply with the requirements of IEC 61000-4-6. Each CDN comes with individually measured data and a calibration certificate for the common mode impedance and the voltage division factor. Further typical data for the phase (not normative) can be found in fig. 2

A variety of calibration adapters and other accessories are available as option. With the included adapter SA USB-C in conjunction with the optional series resistor SR100-6W, the required spacing of 30 mm is obtained as depicted in Fig. 9 of IEC 61000-4-6.

The connection to ground can be accomplished using the ground plane of the CDN. Additionally there is a M4 thread located at the AE side to ground as well as a 4 mm socket to connect the device to ground.

Fig. 1: typ. EuT common mode impedance	Fig. 2: typ. voltage division factor RF-port to EuT-port