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From: linnix on 21 Mar 2010 14:06
In Atmel USBKEY reference design, they use this to protect the signal
lines.

LittleFuse 24V:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=F1320CT-ND

But why 24V to protect the 3V to 5V USB lines?

Tyco used to make a 14V, but gave up also:

http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=PESD0603-140CT-ND

I have not seen anything with lower voltage. Should I just use some
5V to 6V zenars?
From: Vladimir Vassilevsky on 21 Mar 2010 14:10


linnix wrote:
> In Atmel USBKEY reference design, they use this to protect the signal
> lines.
>
> LittleFuse 24V:
>
> http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=F1320CT-ND
>
> But why 24V to protect the 3V to 5V USB lines?
>
> Tyco used to make a 14V, but gave up also:
>
> http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=PESD0603-140CT-ND
>
> I have not seen anything with lower voltage. Should I just use some
> 5V to 6V zenars?

TI has nice parts TDD2E001 and TPD4E001. Designed to protect USB,
FireWire and such.


Vladimir Vassilevsky
DSP and Mixed Signal Design Consultant
http://www.abvolt.com

From: linnix on 21 Mar 2010 14:15
On Mar 21, 10:10 am, Vladimir Vassilevsky <nos...(a)nowhere.com> wrote:
> linnix wrote:
> > In Atmel USBKEY reference design, they use this to protect the signal
> > lines.
>
> > LittleFuse 24V:
>
> >http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=F132....
>
> > But why 24V to protect the 3V to 5V USB lines?
>
> > Tyco used to make a 14V, but gave up also:
>
> >http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=PESD....
>
> > I have not seen anything with lower voltage.  Should I just use some
> > 5V to 6V zenars?
>
> TI has nice parts TDD2E001 and TPD4E001. Designed to protect USB,
> FireWire and such.

They also have clamping voltage of 30V. Does it mean the lines are
unprotected between 5V and 30V? Perhaps I am worrying too much, but
the "power to be" need to know.
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