ESD protection chips

Hi, all,

I'm in the midst of productizing that cotton spark detector that I demoed in the spring, and talked about here a fair amount.

The architecture is a main control panel talking to N integrator units, each talking to 1 to 4 sensor units spaced around the periphery of a medium-large duct (30 cm to 1 m diameter). These detect sparks, but also measure window contamination and air velocity, to make sure that the sensitivity is OK and that the diverter door opens in time to catch the spark and dump it on the ground someplace safe.

The sensors talk to the integrator via Displayport cables, because of the very high signal integrity for the price.

I'm looking at ESD protection for the integrator-to-sensor links.

The analog signals are pretty slow, so 100 ohms in series and 1 uF to ground covers a lot of sins, like 20 kV HBM -> 2V on the cap.

There are digital lines too, though, which need to be somewhat faster than that.

The more capable general-purpose ESD protectors such as the SP720 are a bit on the pricy side for this, but I recall folks here talking about using the input protection networks on some jellybean logic family to do roughly the same job for a lot less dough.

What do you folks use?

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
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Phil Hobbs
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Den onsdag den 17. august 2016 kl. 18.18.30 UTC+2 skrev Phil Hobbs:

we've used PESD3V3L4UG paired with a suitable resistor array for general logic io

-Lasse

Reply to
Lasse Langwadt Christensen

Jellybean logic part input pins are going to give you a resistor, typically 400 Ohms thru diodes to each rail. Is that useful? ...Jim Thompson

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| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
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Jim Thompson

I used the SP720AB in some boards a long time ago, to protect 5 V logic lines connected to the outside world. They seemed to work pretty well.

(I stopped using them, as the voltage level translators that I now use to interface 3.3 V I/O's to the outside seem to be pretty robust.)

Jon

Reply to
Jon Elson

No chips, all descrete. RC (rarely L) and diodes, zeners or rarely TVS.

Having seen sparks leap across 0603 and 0805 during ESD tests I use 1206 for series Rs.

piglet

Reply to
piglet

I had some low-Ohms 1206 thick films on an input fail customer ESD cert. tests the other day. I replaced them with through-hole. Ugly, but worked.

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Best Regards, 

ChesterW 
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ChesterW

Once I had a device that was almost passing ESD and was also very cost sensitive. I put a couple of SMT pads down corner-to-corner as a spark-gap and it shunted enough of the energy for the thing to pass.

Chester

Reply to
ChesterW

What spacing did you use?

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Rick C
Reply to
rickman

I just jiggled it until the design rules stopped squawking.

ChesterW

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ChesterW

That works for us on generic Digital IO suff on a PIC. Sometimes I use a 5.6v zener too. It depends on capactitance, Phil might need a spark gap or discharge tube with low pf.

Cheers

Reply to
Martin Riddle

Dave's eevblog has a spark gap video..

George H.

Reply to
George Herold

Try: SOT143-4 package, by Ca. Micro Devices, Mouser 748-CM1215-02SR (6-year old data).

Reply to
Robert Baer

Obsolete part, but thanks.

Cheers

Phil Hobbs

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Dr Philip C D Hobbs 
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Phil Hobbs

I'm not sure exactly what you're asking but I use all sorts of TVS diodes from

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krw

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