voltage regulator for automotive use

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MrDEB

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awhile back someone posted a site that deals with voltage regulators for electronic circuits.
the standard 78XX series I understand is not stable due to the fact that an automotive electrical system changes value of voltage.
Some company makes special regulators just for automotive use??
 

The concern is high voltage spikes on the input side, and possible reverse polarity if some dummy jumps the car backwards.
 
I have never had problems with any properly designed 78xx regulator on automotive, farm equipment, or industrial applications.
I just use a small in line resistor and a good capacitor on the input. It stops any serious voltage spikes and does the job of any snubber or bypass filter.
All regulator circuits require this, its a standard design requirement with all regulator IC's.
 
Look at the LM293x and LM2940 from ST electronics. They have been designed for the spikes/load dump/reverse polarity etc and are very similar to the 78xx range.

Do however pay special attention to the fact it needs a low ESR output capacitor or you'll end up spending a lot of time trying to work out why your regulator is oscillating.
 
The devices designed for automotive use are not expensive. The auto market is huge and it drives the price down. Why not use parts designed to do the job.

3v0
 
contacted STM

the L4995 looks good but they list a bunch of different units.
the first schematic shows the chip connected to a MCU like it needs it to control voltage??
contacted tech dept with description of needs.
Just a 5v stable supply that needs at max 100ma.if I use the LM386 amp in my design.
 
LM2937 500 mA LDO regulator


 
There are plenty of cheap ways to give a decent level of overvoltage protection.

The easiest is to just add a 33V zener in parallel with the supply.

A crowbar is also another good idea but it does have the disadvantage of taking out a fuse whenever there's a spike.

A zener and crowbar with a low pass filter and possibly using a poly fuse instead of a one shot fuse provides pretty tough overvoltage protection.

I'll post a schematic tomorrow if you don't understand what I'm saying.
 
Im actually looking for an automotive application as well, somthing a cap to make headlights and interior lights dim after usage.
 
It is a good idea to check when you see a price spread like this but it does happen. It is more common when two chip makers source the same part. Possibly because the reseller has purchased one item in bulk but not the other.

Both parts share a single datasheet so I expect them to be the same.

The less expensive part has a P code
Promotional Price: A discounted price as a result of a Newark product promotion.
Click to expand...
If you look at the cost per unit breakdown you will see they are selling a single unit at the 10,000 unit price. Stock up before they change their mind.
 

thanks.. I'll go for it

In the data sheet of LM2937 (https://www.electro-tech-online.com/custompdfs/2009/05/LM2937.pdf) it says:

The LM2937 is a positive voltage regulator capable of supplying
up to 500 mA of load current. However, this current can be supplied only when the input to
output voltage differential is greater than 3V.

How many current would you think this regulator would supply if the input voltage is 14V and output voltage is 12V (less than 3V).. would it be sufficient to power a 12V LED?
 
Last edited:
I read this.

With
a load current of 500 mAthe minimum input to output voltage
differential required for the output to remain in regulation is
typically 0.5V (1V guaranteed maximum over the full operating
temperature range).
Click to expand...

And this

Special circuitry has been incorporated
to minimize the quiescent current to typically only
10 mA with a full 500 mA load current when the input to
output voltage differential is greater than 3V
Click to expand...
talkes about quiescent current ... the first is what you are interested in.

So yes if you have 1 volt about 12V you can regulate to 12V.
 
3v0 said:
talkes about quiescent current ... the first is what you are interested in.
Click to expand...

thanks.. you've been very helpful

so the LM2937 and a low ESR capacitor (below
3Ω) is all I need ?

sorry if the question sounds stupid.. I'm new to this
 
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