Author Topic: Single bi-directional TVS = two uni-directional TVSs back to back ?  (Read 2074 times)

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Offline BravoVTopic starter

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I need 300V bi-directional TVS, but in hands only have the uni-directional version.

As the forward voltage is insignificant compared to VBR which is at 300Volt, is this doable ?

Max. power dissipation capability in that configuration is also doubled right ?

Offline Zero999

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Re: Single bi-directional TVS = two uni-directional TVSs back to back ?
« Reply #1 on: December 27, 2018, 10:06:15 am »
A TVS diode behaves like an ordinary diode when forward biased so yes, connecting two unidirectional ones back-to-back will work.

The maximum power dissipation is only doubled if the over-voltage is AC and has equal positive and negative components.
https://www.mouser.com/pdfdocs/Semtech_Application_Note_TVS_Diode.pdf
 
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Online tszaboo

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Re: Single bi-directional TVS = two uni-directional TVSs back to back ?
« Reply #2 on: December 27, 2018, 11:30:42 am »
Yes. I've seen people do this all the time. For example one chap was doing it for RS485, he had a 12V and a 7V TVS diode on it. Poor chap had no idea how to design circuits properly.
 

Offline BravoVTopic starter

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Re: Single bi-directional TVS = two uni-directional TVSs back to back ?
« Reply #3 on: December 27, 2018, 05:38:48 pm »
@Zero999 , thank you ! :-+

Yes, its for AC , related to my other thread for building an AC soft starter for inductive load.

Offline T3sl4co1l

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Re: Single bi-directional TVS = two uni-directional TVSs back to back ?
« Reply #4 on: December 27, 2018, 10:50:23 pm »
In fact, the high voltage ones are typically stacks of ~30V parts -- they even build their SPICE models this way, and it gives more energy handling.

Tim
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Offline BravoVTopic starter

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Re: Single bi-directional TVS = two uni-directional TVSs back to back ?
« Reply #5 on: December 28, 2018, 12:58:24 am »
So each of them maxed out only at 30V ?

Offline T3sl4co1l

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Re: Single bi-directional TVS = two uni-directional TVSs back to back ?
« Reply #6 on: December 29, 2018, 01:34:36 am »
So each of them maxed out only at 30V ?

Each of what?

Each of the dies, it seems that way; but unless you're buying dies, I don't see that's a concern.

Tim
Seven Transistor Labs, LLC
Electronic design, from concept to prototype.
Bringing a project to life?  Send me a message!
 

Offline BravoVTopic starter

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Re: Single bi-directional TVS = two uni-directional TVSs back to back ?
« Reply #7 on: December 29, 2018, 01:50:57 am »
Each of what?

Each of the dies, it seems that way; but unless you're buying dies, I don't see that's a concern.

Tim

No, not my concern  ;D, you just made me aware of it, thanks.

Briefly at TVS datasheet, and looks like 30V dies stacking is at >= 200V.


Offline BravoVTopic starter

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Re: Single bi-directional TVS = two uni-directional TVSs back to back ?
« Reply #9 on: December 29, 2018, 04:23:03 am »
Spec, I am not looking for datasheets, thanks though.

Offline spec

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Re: Single bi-directional TVS = two uni-directional TVSs back to back ?
« Reply #10 on: December 29, 2018, 04:41:27 am »
Spec, I am not looking for datasheets, thanks though.
Ah sorry. Misread your OP. :-[
 


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