AW: multiple power supplies in a modular

[Barry L Klein]

TVSD = Transient Voltage Suppression Diode
They are zeners with a large surface area to dissipate the heat from the clamp.  They are very fast and don't degrade like MOV's(varistors).  They have spec'd DC clamp voltages that go really low if you want them (MOV's don't go very low).  MOV's are best for very short ESD type of issues.  TVSD's kill those and can also dissipate much larger amounts of current until your crowbar saves your system (if you choose the right ones).  For instance on our drives, with a typical pc supply a short of 12V to the 5V line on the drive will hopefully shut down the supply and not blow all the 5V components.  As such, our drive may even be protecting your system(?)!   But if you have a nasty failed supply that with a bad crowbar the TVSD's will go first, then everything else (which would have happened anyway without em).

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From: 	CZECH at INTERMETALL.DE[SMTP:CZECH at INTERMETALL.DE]
Sent: 	Tuesday, February 10, 1998 12:56 AM
To: 	SYNTH-DIY at MAILHOST.BPA.NL; BARRY.L.KLEIN at WDC.COM
Subject: 	Re: Re: AW: multiple power supplies in a modular

<<File: IST83A4124_2.txt>><<File: IST9004124_3.txt>>
SNIP>

> As a result of my work, we put TVSD's across the drive supply lines.  These will clamp any overvoltages.  You might want to try these things on your supply lines etc.  They seem to be worthwhile.  Definitely have improved reliabilty of the product.  And I think only ours have em....(plug)  :-)

Very interesting. 
But I have some questions.
A TVSD is also called varistor, i.e. a polycrystaline semiconductor
device with some defined breakdown charcteristic (what do the letters
stand for?)?  What are the data of the devcices you use?  Breakcown
voltage, max. current, what is the supply voltage these device have to
protect.

Please some answer.

m.c.

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