Protection of USB 2.0 Applications Series: ESD-confirm USB Interfaces

The USB-Interface might be the most distributed PC interface in the world. Usage in industry-applications is more and more common. Let’s have a closer look to the special environmental conditions of industry applications.

There are real concerns regarding the robustness against EMI and ESD written in Intel’s “ High Speed USB Platform Design Guidelines”. Intel recommends the usage of a common mode choke for EMI suppressions and another component for protection against ESD pulses.

Wurth Electronics offers all these types of products:

• The WE-CNSW common mode choke was developed for EMI suppression on high speed signal lines.

• For ESD suppression the TVS diode arrays WE-TVS with very low capacitances (<2pF) or the ESD Suppressors WE-VE (capacitances down to 0.05pF) are your preferred choice.

For outstanding EMI behavior, it is absolutely necessary to protect the power supply (Vbus) as well. A lot of design engineers forget this important point and wonder why their product don’t pass all the tests in EMI lab.

Two typical schematics for optimized protection of one or two USB ports are above.

With one TVS diode array WE-TVS you can fully protect two USB lines. All four signal lines as well as the common power supply are well protected.

For further optimization, i.e. to filter incoming common mode noise as well as differential mode noise from USB line, a LC filter is built with the common mode choke WE-CNSW and the capacitors.

For power supply lines, very good noise suppressions can be reached with a chip bead ferrite, like the Wurth Electronics WE-CBF series. In contrast to the shielding of the dataline, no low capacitive ESD suppressor is necessary at the power supply shown above.

Single line protection components like ESD suppressors series WE-VE also have to be connected from signal line to GND. For power line protection it is not necessary to use a low cap ESD suppressor, you might prefer a standard SMD varistor which can withstand higher surges and higher transient energies.

Protection of USB 2.0 Applications Blog Series Continues

Check back in for more USB application protection tips as we dive into TVS Diodes, ESD Suppressor details, and much more ahead!

To request a quote or to order samples of products to protect your USB ports, click here.

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