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What advice do you have for conditioning D+ and D-?

Last Updated: September 05, 2011

What advice do you have for conditioning D+ and D-?


For a well-designed product using our devices to meet the FCC/CE requirements, no additional external components should be necessary for either EMI/RFI or for ESD/EFT. Even the filter components we show on the power lines of our reference devices should be unnecessary if sufficient care is taken with the design.

However for more demanding environments (such as industrial) where the requirements are greater than the normal domestic/commercial/light industrial, in order to meet signal quality requirements, it is very difficult to use filtering components such as ferrites on the D+ and D- lines, and I would not recommend it. Clamping a small ferrite on the lead will work - the Microsoft mouse is an example of this. 

For transient suppression there are various devices that could be used on the chip side of the 20-ohm resistors on any hub port. 
There are devices such as the AVX transguard, staticguard, etc (see Most of the passive component manufacturers make this type of device.

Metal Oxide Varistors (MOVs) might be applicable, but they might be a bit slow, but they are possibly the cheapest solution.
There are also active devices, which are basically fast zener diodes - often called Tranzorbs. They tend to be made by smaller, specialist companies - a good place to start is,1121,0_0_353170,00....

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