Author Topic: TVS diodes  (Read 801 times)

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Offline stj

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TVS diodes
« on: January 26, 2018, 09:57:13 pm »
i have to replace one,

the original is bi-directional.

i have some uni-directional ones,
can i use 2 in series or anti-parallel??
 

Offline helius

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Re: TVS diodes
« Reply #1 on: January 26, 2018, 10:08:21 pm »
Use them in series with their cathodes together.
 
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Online wraper

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Re: TVS diodes
« Reply #2 on: January 27, 2018, 01:30:32 am »
i have some uni-directional ones,
can i use 2 in series or anti-parallel??
No, it would be just as 2 diodes anti parallel, therefore clamping at below 1V. Do as helius suggested.
 

Offline stj

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Re: TVS diodes
« Reply #3 on: January 27, 2018, 03:23:02 am »
so -----|>|--|<|--------

hmm - gonna be fun working out the placement - probably have to be a "tent" style - it's all smd  ;D
 

Online wraper

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Re: TVS diodes
« Reply #4 on: January 27, 2018, 09:42:52 am »
Depending on circuit you could just use one unidirectional TVS. I cannot think of that many circuits which would actually require bidirectional TVS.
 

Online NANDBlog

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Re: TVS diodes
« Reply #5 on: January 27, 2018, 10:56:53 am »
Depending on circuit you could just use one unidirectional TVS. I cannot think of that many circuits which would actually require bidirectional TVS.
RS485. The common mode voltage could easily be negative.
 

Online wraper

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Re: TVS diodes
« Reply #6 on: January 27, 2018, 11:00:17 am »
Depending on circuit you could just use one unidirectional TVS. I cannot think of that many circuits which would actually require bidirectional TVS.
RS485. The common mode voltage could easily be negative.
Yep, pretty special cases like this. Usually when I see bidirectional TVS in a circuit, there is no good reason for ir being bidirectional.
 

Offline floobydust

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Re: TVS diodes
« Reply #7 on: January 27, 2018, 01:55:22 pm »
Many RS-485 bi-directional TVS are lop-sided.
Example SM712 has +7, -12V clamps. I know it is a tiny flea fart TVS, with fake 400W spec (SOT-23), but designed for max. according to RS-485 standard.
 

Offline SeanB

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Re: TVS diodes
« Reply #8 on: January 27, 2018, 01:59:48 pm »
Bidirectional is good from a buyer's side, you only need a single part for all applications, and putting it it the wrong way round does not cause any issues. If you need unidirectional you just use a regular diode in parallel as well. Yes you will need to build a tower to use the unidirectional ones to replace a bidirectional one though.
 


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