Author Topic: Need 0805 transient suppression diodes  (Read 1914 times)

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Offline AndersJTopic starter

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Need 0805 transient suppression diodes
« on: February 29, 2016, 04:25:09 pm »
Are 33-39 Volt transient suppression diodes available in size 0805?
"It should work"
R.N.Naidoo
 

Offline T3sl4co1l

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Re: Need 0805 transient suppression diodes
« Reply #1 on: February 29, 2016, 05:26:03 pm »
Yes...

They won't handle much power or energy. What do you need them to protect against?

Tim
Seven Transistor Labs, LLC
Electronic design, from concept to prototype.
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Offline AndersJTopic starter

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Re: Need 0805 transient suppression diodes
« Reply #2 on: February 29, 2016, 06:06:05 pm »
1 KV  surge, IEC 61000-4-5.
Hoping to be able to replace 0805 1 nF caps for better surge immunity on already made pcb's.

Currently all I have is 1nF/50V to gnd, ferrite bead, 1nF, 10K series, and then diode clamps to Vcc/gnd.
Perhaps this is good enough, I don't know yet, just looking for options in case this fails.

The above components divert surges to signal gnd, which floats vs chassis gnd.
I would like to divert to chassis, but I also have a Hi-Pot requirement of < 0.5 mA leakage
to chassis gnd at 710 Vdc between signal gnd and everything else tied together.


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R.N.Naidoo
 

Offline T3sl4co1l

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Re: Need 0805 transient suppression diodes
« Reply #3 on: March 01, 2016, 05:13:44 am »
1kV surge, for a signal line, is going to be in the 50A range!

I doubt you'll find any TVS diodes rated for that.  MOVs seem plausible:
http://www.digikey.com/short/33fq3v
It'll definitely be better than the capacitor, but you'll be lucky if it survives one shot of full power, I think.  The peak voltage won't be very friendly... you'll want to keep the series resistor.

You could add a GDT to GND (this is suitable practice for a TNV circuit), but because the breakdown voltage has to be high enough to meet your hi-pot requirement, it probably won't do much (a 700V GDT might fire at >1.5kV, missing the 1kV surge).

Good luck,

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