Author Topic: ESD diode which gnd to use  (Read 890 times)

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Offline rakeshm55Topic starter

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ESD diode which gnd to use
« on: February 20, 2019, 05:38:16 am »
Hi,
My understanding is to connect external ESD diodes to device ground. eg for GPIOs ESD diode will be connected from GPIO to digital ground.

I happen to see schematics of AM5728 http://www.ti.com/tool/tmdsevm572x?jktype=tools_software#1

Here the ESD diode is connected to chassis rather than device ground. What is the reason?? Which the recommended practice??
Please share some literature if any
 

Offline bson

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Re: ESD diode which gnd to use
« Reply #1 on: February 20, 2019, 09:18:48 am »
The chassis is normally connected to the mains third prong, a good place for ESD to go.
 
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Online exe

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Re: ESD diode which gnd to use
« Reply #2 on: February 20, 2019, 09:34:03 am »
Interesting. I'd say ESD kills by creating dangerous difference in potential. On you picture the IC itself is connected between Vcc and digital ground. I'd clamp output with two diodes to IC ground.

I see it uses audio jacks or something. In such connector usually ground is connected first. But not sure if this can cause problems here or not.

Would like to know more.
 

Offline T3sl4co1l

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Re: ESD diode which gnd to use
« Reply #3 on: February 20, 2019, 09:42:23 am »
You could still have a charged cable transient, but that too is unlikely due to how audio jacks tend to wipe across ground.

My complaint is more basic, there are three different grounds shown in this schematic.  There might be good reasons to do this, but they get less and less probable as the number of grounds go up.  For the part shown, in and of itself, it's only a hazard.

Tim
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Online exe

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Re: ESD diode which gnd to use
« Reply #4 on: February 20, 2019, 10:00:10 am »
I don't see grounds connected. Can this cause problems? I mean, the output is clamped to chassis, but not the IC ground. So, an ESD event on IC ground can potentially go through the IC itself.

Or, put another way: input has two wires, and both of them should be clamped to power rails. Am I correct?
 


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