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From:	"Luis de Arquer (ldearquer AT gmail DOT com) [via geda-user AT delorie DOT com]" <geda-user AT delorie DOT com>
Date:	Mon, 26 Nov 2018 23:06:16 +0100
Message-ID:	<CAGqyy=bCkYxADbRhjfAeCkt2bOccMGUDFHMRy5myyXWjZ3s8_w@mail.gmail.com>
Subject:	Re: [geda-user] [off-topic] 24V automotive (truck) design issues
To:	geda-user AT delorie DOT com
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Hi Richard,

There are quite a few spikes that can damage electronics on the
truck. You can find most of them on ISO 7637 (second part has the
pulses definition). The worst I can remember for car is -150V for 2ms
approx, surely more on trucks. Positive pulses of over 100V happen
often when parallel inductive loads are disconnected (such as windows,
etc), but this are normally under 100us.

Load dump is fairly unusual though, since that requires the battery to
be removed from the truck while alternator is running. Its strength
depends on whether the truck has load dump supressor or not (cars now
normally have it, but I don't know trucks...). With load suppresor,
you may see about 58V for up to 300-400ms. It is currently defined in
ISO 16750-2 (2012 or later).

This may help:
- Try to get the boards that failed for analysis. Did the TVS fail?
- Revise all input capacitors voltage ratings
- It can help having a high voltage series diode at the input such as
BAV21W, followed by a tanky 220uF or higher capacitor: This should get
rid of most pulses, except load dump.
- For load dump, you really need to know if there is a supressor or
not. The difference is huge.

Best regards,
Luis

2018-11-26 18:40 GMT+01:00, Richard Rasker (rasker AT linetec DOT nl) [via
geda-user AT delorie DOT com] <geda-user AT delorie DOT com>:
> Hi John,
>
> Op 26-11-18 om 17:56 schreef John Doty:
>> Lots of info out there, google "load dump protection”.
>
> Ah, great, thanks! I never heard of this phrase before (hey, that's why
> I asked here) -- this really helps!
>
> Right away, I see that quite a bit of extra protection is in order --
> but it was a prototype anyway.
>
> Thanks again,
>
> Best regards,
>
> Richard Rasker
>
>
>
>

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