TPD2E2U06: ESD Protection Bi Directional vs Uni Directional

JIGAR PATEL2

Intellectual 615 points

Part Number: TPD2E2U06

Hi All,

I want to protect whole USB port on my custom board from ESD.

For that TVS diodes(ex. TPD2E2U06) are used. That is ok.

Now,

There are lots of document which describe difference between Bi Directional & Uni Directional ESD Protection Diode. (I got reference from below link)

https://www.mouser.com/pdfdocs/AND8424-D.PDF

If you have positive as well as negative voltage on your line with respect to ground, then use Bi Directional ESD Protection Diode &

If you have only positive OR only negative voltage with respect to ground, then use Uni Directional ESD Protection Diode.

In USB,

Uni Directional ESD Protection is used on VBUS line, that is ok

But why Bi Directional ESD Protection used on data line?, they have either positive logic or ground logic (i.e. logic 1 or logic 0).

They don't have negative voltage logic with respect to ground on data line.

Also, if you use Bi Directional ESD protection on Uni Directional line, then will it damage on line when opposite voltage spike present on it?

Regards,

Jigar

over 6 years ago

0 JIGAR PATEL2 over 6 years ago

Intellectual 615 points

"But why Bi Directional ESD Protection used on data line?, they have either positive logic or ground logic (i.e. logic 1 or logic 0)."
This sentence misleading, sorry for that.

On low and full speed devices, a differential ‘1’ is transmitted by pulling D+ over 2.8V with a 15K ohm resistor pulled to ground and D- under 0.3V with a 1.5K ohm resistor pulled to 3.6V. A differential ‘0’ on the other hand is a D- greater than 2.8V and a D+ less than 0.3V with the same appropriate pull down/up resistors.

But in all case voltage remains positive, it will not go to negative with respect to ground.
Then why Bi Directional ESD Protection is used?

Regards,
Jigar

0 Matthew Xiong over 6 years ago in reply to JIGAR PATEL2

TI__Prodigy 595 points

Hi Jigar,

You are correct in saying that unidirectional ESD diodes are optimal for unidirectional interfaces such as USB data. However, since bidirectional diodes have a symmetric Vrwm range, there's no reason it cannot support USB data signals as well. However, one thing to watch out for is the negative clamping voltage which you mentioned as well. Sometimes, bidirectional devices do not clamp well enough for negative ESD but this is not always the case.

If the diode is a single channel bidirectional diode, then any pin can be connected to IO and the other pin to ground. This gives manufacturers the benefit of not worrying about the polarity of the package.

I've also attached my blog here which explains all of this in more detail.

e2e.ti.com/.../esd-fundamentals-part-5-reverse-working-voltage-breakdown-voltage-and-polarity-configuration

0 JIGAR PATEL2 over 6 years ago

Intellectual 615 points

"if you use Bi Directional ESD protection on Uni Directional line, then will it damage on line when opposite voltage spike present on it?"
I want to give brief on this.

ex.
one I/O line has 3.3V(logic 1) or ground(logic 0).
If I use 5V Uni Directional ESD protection diode, then

if positive spike comes, ESD Protection diode supress it to 5V.
if negative spike comes, line goes (ESD Protection diode) diode drop low with respect to ground.
This will not damage the line.

but if i use Bi Directional ESD Protection diode on this line,
ESD Protection diode supress positive & negative spikes to +/-5V.
Here is the problem.
In negative Spikes, ESD Protection diode will allow the line to go up to -5V. This will damage the line? isn't it?

0 Matthew Xiong over 6 years ago in reply to JIGAR PATEL2

TI__Prodigy 595 points

Hi Jigar

If a positive spike comes, the ESD protection diode will suppress it to it's clamping voltage, not necessarily 5V. Whether or not this clamping voltage damages your line will depend on your system tolerance as well as the clamping voltage/Rdyn of your diode.

If you use bidirectional and positive or negative spikes occur, the diode will suppress up to its positive and negative clamping voltages (respectively). This does not always mean that it will damage your line. Again, it depends on your system. I wrote a blog series recently that helps explain the key specs/features of ESD diodes. Feel free to take a look through them. "Part 3: clamping voltage" will explain what I've said here in more detail.

e2e.ti.com/search

0 JIGAR PATEL2 over 6 years ago in reply to Matthew Xiong

Intellectual 615 points

Hi Matthew Xiong,
Thanks for your quick replay.

I have gone throw your blog. It is great.
can you suggest me the part number which is in SOT package?
Will this part applicable to all the lines (i.e. VBUS, D+, D-) or only for data lines.
If only for data lines then kindly suggest me the part number for VBUS.

I have one query which i have already mentioned below post.
Kindly guide me if i am wrong in that.

0 JIGAR PATEL2 over 6 years ago in reply to Matthew Xiong

Intellectual 615 points

Ok,
I will go throw this blog & will replay you if any query is there.

Thanks for your guidance.

Regards,
Jigar

0 Cameron Phillips over 6 years ago in reply to JIGAR PATEL2

TI__Genius 12410 points

Jigar,
In response to your negative strikes question, it may damage or it may not it depends on your IC. For best protection you would want to use unidirectional if your signal doesn't swing below ground.
Also for a list of our parts in that package go to www.ti.com/.../products.html and search for the package you would like.

Regards,
Cameron

0 JIGAR PATEL2 over 6 years ago in reply to Cameron Phillips

Intellectual 615 points

Thank you Cameron & Matthew Xiong for the guidance.

Dear Matthew Xiong,
The Blog you have written on ESD Protection is very helpful to understand the parameters related to ESD Protection Diode & concept.

Regards,
Jigar

0 Matthew Xiong over 6 years ago in reply to JIGAR PATEL2

TI__Prodigy 595 points

Hi Jigar,

Happy to help! Feel free to reach out again if we can be of any assistance!

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TPD2E2U06: ESD Protection Bi Directional vs Uni Directional