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Electronics => Projects, Designs, and Technical Stuff => Topic started by: hal9001 on May 06, 2021, 09:13:09 am

Title: Which ESD diode to use?
Post by: hal9001 on May 06, 2021, 09:13:09 am

How do you choose what ESD diode type to use? Specifically want to understand which to use for USB2.0 data but there are  different app notes showing different diodes.

(https://www.eevblog.com/forum/projects/which-esd-diode-to-use/?action=dlattach;attach=1217213)

(https://www.eevblog.com/forum/projects/which-esd-diode-to-use/?action=dlattach;attach=1217215;image)

Cheers

Title: Re: Which ESD diode to use?
Post by: hal9001 on May 07, 2021, 10:01:49 am

Does the speed of the bus determine which ESD/TVS to use? Can any one point me to more information for which one to use and why?

Title: Re: Which ESD diode to use?
Post by: TimNJ on May 07, 2021, 05:39:52 pm

Signal line ESD suppressors often need to be low capacitance. For high speed USB 2.0 data rates/edge rates, probably can get away with relatively high capacitance..maybe a few pF (~5pF) is okay. For higher speed buses like USB 3.0, you probably need sub 1pF or so.

I am not sure if the semiconductor properties of the low-capacitance diodes have any disadvantages.

Otherwise, to size a ESD/TVS diode correctly, you should consider the "energy behind" the ESD pulse. If the energy source is limited, you can use a a physically smaller diode. If higher energy source, need a physically larger diode to not melt it!

Title: Re: Which ESD diode to use?
Post by: thinkfat on May 07, 2021, 05:52:58 pm

What's wrong with just using an integrated standard solution? USBLC6-2SC6Y?

Title: Re: Which ESD diode to use?
Post by: warpigs330 on May 07, 2021, 06:56:03 pm

Not the OP but wondering about the same thing. I am getting boards made by JLCPCB and am trying to reduce the number of extended components I need to pay for, so if I could replace this ship with basic diodes it would save a little money.

Title: Re: Which ESD diode to use?
Post by: hal9001 on May 07, 2021, 09:08:18 pm

Thanks all. To be more clear,I would want to know when to use which type of protection diode in the picture.
Documents from companies like Wurth and Nexperia recommend different types for the same bus type(USB2.0 specifically). Are they interchangeable for ESD protection?

(https://www.eevblog.com/forum/projects/which-esd-diode-to-use/?action=dlattach;attach=1217564;image)

Title: Re: Which ESD diode to use?
Post by: nctnico on May 07, 2021, 09:30:37 pm

If it says USB protection diode in the datasheet then it is suitable for that purpose. Don't get too hung-up on the actual symbol. What is more important are the ratings for the amount of charge it can handle and what kind of requirement you have for that.