Surviving automotive load dump

Yep a whole 10dB improvement in 30+years

martin

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datasheets.

Nobody said that. Bond wires provide one limit on higher power devices (high power being a relative term).

I don't know of any microcontroller I/Os that are high enough power to make the bond wire limits relevant. The RDSon of the microcontroller outputs is probably 3 orders of magnitude higher than that of a low resistance 75V power MOSFET in a TO262.

Robert

That's a different kind of transient from a load dump - higher voltage but much less energy.

-- Joe Legris

more stuff

martin

Talk to an automotive supplier. These switches don't seem to quite reach your anticipated voltage levels but show some of the tricks of the trade:

Watch out for some peculiarties like turn-on during spike etc. It might not be what you want.

Anyhow, I'd probably crowbar it out if it can be safely done in your application.

How about an NTC and a zener?

How about an NTC and a zener? I meant a PTC ofcourse :-)

Wow, what a great thread. Plenty of useful links, and it hasnt (yet) denigrated into irrelevancy

Cheers Terry

Not sure if it's been mentioned, but load dump is covered in ISO 7637.

Cheers

PeteS

Wouldn't that punch a hole into it once the abs max gate voltage is exceeded?

How can VGSmax be exceeded in such a setup?

The zener approach bothers me because large voltages CAN be developed.

Also, when the transient clears you run the risk of a large body-diode current.

...Jim Thompson

Must have misunderstood you. If you had a "follower" in mind then it can't be exceeded.

Most automotive circuits I have seen used the transzorb scheme where there was a huge device that shunts spikes to ground. Probably fine but if people employ MOVs for that they have to keep in mind that there is a finite number of spikes those can take.

What really surprised me was that in college I drove my old Citroen without battery for years because 6V batteries were so expensive. Load dumps galore. The nightmare for its little electric grid must have been the huge compressor for the aftermarket trucker's horn I installed. Yet nothing ever died.

What? A 2CV ?:-)

It probably had a GENERATOR with an electro-mechanical regulator.

Did it even have any accessories ?:-)

...Jim Thompson

T'is the one.

Yes. But the brushes were, well, marginal and I put a little wood stick under the counter-weight of the regulator to provide more oomph for the radio.

The original number of electronic components in that car was zero. Not even a diode. But I had a shortwave radio in there, and a cassette player, 6V-12V inverter and some other stuff.

I just had to make sure I didn't tap that truckers horn when idling or the engine would stall. Same for the headlights and here the factory must have anticipated such "frugal" usage because there was a handle that could be reached easily like the turn signal. In France it used to be customary to drive through cities with just the position lights on.

'Twas so in 1994.

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

What really scared me was when a guy polished off a whole 700ml bottle of Cote du Rhone with lunch, walked across the parking lot, hopped into a 40-ton rig and fired her up.

So ?:-)

...Jim Thompson

Well, he didn't have a big lunch with it. Just a small sandwich plus two or three hand-rolled Gauloises.

What is that----------^^^^^^^^^ ??

...Jim Thompson