That doesn't mean the know-how they created went away as well. Motorola published most excellent application notes and books, many of which I have kept. In the same way that Unitrode literally wrote the book on SMPS design, still very relevant despite the fact that TI swallowed them in the last century.
-- Regards, Joerg http://www.analogconsultants.com/
n t
--
h)
a whole lot of the protected fets specific for automotive use have
42Volt clampingI'm sure funny things happen when relays, lamps and fuel injectors start to turn on from the driver fets clamping, can't be happening very often?
-Lasse
I have never seen it this bad but other say they have:
http:/
What I know for sure is that 40V doesn't cut it, I have seen in excess of 60V. It happens when the battery connection briefly lets go. The usual, where you have a car with a fairly dirty engine compartment, the battery hasn't been serviced in years, green and white stuff is growing around its terminals. It can also happen when a battery fails. In some commercially used vehicles and in race cars there is a disconnect switch and when that gets turned while the alternator is charging you are pretty much guaranteed a big transient. I have driven trucks (in Europe) where this key was near the front of the seats. Wearing heavy work boots you wouldn't even feel it if you accidentally hit it.
-- Regards, Joerg http://www.analogconsultants.com/
kin
hat
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they also mention 42V
The kill switches I've seen have two switches, one that cuts the battery another that shorts the alternator with ~3R, so assuming I know how it works you'd need to be charging the battery with more than ~5A to get a spike at all
wouldn't the charging current have to be something like 75% of the total load on the alternator to get a 60V spike?
now if you turn a big load right at the time when the battery disconnects I can see bad things happening
-Lasse
It's called a "Load Dump". You have a vehicle with a flat battery being jump started, and the alternator is changing at full current when the leads are removed leaving nowhere for the charging current to go...
In the automotive compliance lab, the standard Load Dump test is to apply a huge bank of electrolytic caps charged to umpteen volts to the test device and see if it is damaged. The results can be quite spectacular. All the dial lights go off like flash bulbs.
Lots of fun. The design engineers hated it.
Do a Google on "Load Dump test".
................... Zim.
I can remember my father talking of building a fire under the crankcase of his model-T ;-)
[Using remote access from Rancho Mirage, CA, HI Express, thru my home computer, first try of my remote access :-] ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
When I did designs for Chrysler, all electronics had to adhere to their internal standards. AFAIR: 14.5V nominal; a device should maintain normal operation from 10V to 18V for indefinite time, a device should survive continuously applied 24V for indefinite time without damage however it doesn't have to be operable, a device should survive a load dump test (that is a burst of ~10ms ~100V pulses).
A healthy TVS with ~27V rating is pretty much a design requirement. I would also recommend the automotive grade regulators (usually guaranteed up to the input of 40..60V).
There is also a lot of requirements on the current drain in shutdown, EMI/EMC, wakeup time, etc. etc. etc. All of that is pretty uneasy to satisfy, especially within the cost constraints.
Vladimir Vassilevsky DSP and Mixed Signal Design Consultant
I personally have seen 400V :-( ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
On a sunny day (Fri, 01 Jul 2011 21:17:46 -0700) it happened Jim Thompson wrote in :
Anybody seen 401?
On a sunny day (Fri, 01 Jul 2011 13:27:56 -0700) it happened Joerg wrote in :
This was suggested on top of the other counter measures. A 7805 cannot handle 40 V either, only 35. So stop that PHUT shit, and try reading in context.
Hi Jim! So, you are just across the valley from here! We oughta get together for lunch... ;-)
Charlie
Thought of that, even looked up your location, but no time today... heading right back to Phoenix.
Next time ?:) ...Jim Thompson
--
| James E.Thompson, CTO | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona 85048 Skype: Contacts Only | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
No kidding. The spikes could be very nasty if your electronics happens to be on the same wire with an electric motor like windshield wipers or something like that.
Vladimir Vassilevsky DSP and Mixed Signal Design Consultant
On a sunny day (Sat, 02 Jul 2011 10:54:59 -0500) it happened Vladimir Vassilevsky wrote in :
Oh, I know that, even a relay coil can do it, especially with a bad corroded connection to the car battery.
400 V is a lot though, 10x Vbat is what one should expect. The amount of enery in those pulses should not be that much, you could clamp it with some series inductance, R, and a big transzorb.But then has anybody looked at those cigar lighter power adaptors for laptops and other gadgets? I must have 3 or 4 laying about now :-) I know those have a fuse in it, and a switcher, but the rest?
Exactly. It was a good app note. It explained the failure mechanisms in the vehicle and how they would propagate to the 12V supply.
But there *is* a lot of energy in a true load dump pulse - hundreds of Joules potentially.
-- John Devereux
42V abs max is only safe if you clamp with a massive TVS. And that better be really big and far away from anything combustible. I would not design automotive electronics with a 42V device. But when it comes to vehicles my stuff is usually for aerospace and there were have much more exacting standards to follow, for example DO-160 for American aircraft.
All the ones I same simply disconnected the battery and that was it. On the trucks we called it "the bone" because it looked like one and was detachable. Every trucker had one on his key chain.
Picture a really cold winter day. The driver lets it crank and crank and crank. Finally when the battery is almost beginning to give up the engine rumbles to life. Now the alternator will begin to charge the exhausted battery back up at a very high current because the regulator tells it to. Then the battery succumbs and pops open circuit. Light comes on at the dashboard (on older cars it might not). If the electronics weren't protected against this load dump a modern car's engine would now stall and the car would need a tow (versus just a new battery). That can mean thousands of Dollars of difference to the driver plus some major inconvenience.
-- Regards, Joerg http://www.analogconsultants.com/
I don't have a crystal ball. You suggested a LM2596, I advised against that. It's up to the OP.
-- Regards, Joerg http://www.analogconsultants.com/
Jim Thompson wrote in news: snipped-for-privacy@4ax.com:
Say,Jim,do you know anything about automotive LED brake lights? what sort of LEDs they're using,how they drive them or regulate the current,how they affect the turnsignal flasher circuit are what I'm curious about.
I've been counting the number of LEDs different cars use for their brake lights,and wondering how they're wired,parallel series-strings,all parallel,all-serial? with parallel and parallel-series,at least if one LED dies,you don't lose the entire array. And all-serial seems like they would need some higher voltage supply,greater than 13V nominal. (Figuring ~2V per LED.)
the old Edison lamps put a heavier load on the flasher and if a bulb died,then some flashers would not flash...not enough current draw. So,changing to LED lamps would have the same effects,I guess. Perhaps the newer cars use a different type of flasher circuit.
-- Jim Yanik jyanik at localnet dot com
Some folks let out the oil when they got home, put it on the stove, and poured it back into the engine in the morning.
So you let the 'puter at home run all that time? Yikes. I can access email through a server in Kansas (my web host) and Usenet through a server in Berlin, Germany (my Usenet host). Doesn't matter where I am on the planet, as long as the place has an Internet connection.
-- Regards, Joerg http://www.analogconsultants.com/
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