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 Automotive Voltage Regulator for MCU
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Posted - Jan 20 2017 :  04:31:39 AM  Show Profile  Reply with Quote
To supply 5V to a PIC in a 12-15V automotive environment, I have so far been using variants of 7805s, or the HV varieties of PIC.

While they work, obviously they aren't really of sufficient protection for the environment. In particular reversed polarities, and battery 'jump starts' can cause problems of the destructive variety.

My circuits draw very little current (100mA is a typical maximum) and I solder through hole by hand, so I would avoid SMD.

Can anybody recommend either a good way to protect a simple 7805 (or 78L05), or some alternatives to the 7805 that are more suitable for the environment? I have so far found a suggestion of LM2937(datasheet:http://www.kynix.com/uploadfiles/pdf2286/LM2937ES-12.pdf), but this is relatively very expensive (some 10x more than a 7805)

As a side question, is there a good way to find automotive grade components? I usually use farnell's catalogue, but they don't seem to have 'automotive' in their parametric search so it is a matter of scouring datasheets, which is time consuming.

Aaron Cake

6715 Posts

Posted - Jan 21 2017 :  10:24:29 AM  Show Profile  Visit Aaron Cake's Homepage  Send Aaron Cake an ICQ Message  Send Aaron Cake a Yahoo! Message  Reply with Quote
As for protecting power inputs, take a look at the power section of the Megasquirt V3 here:

Basically consists of a MOV, inductive filter and some blocking diodes. My experience has been that the input protection is absolutely adequate. I used a variation of the same design when I recently designed and built an Arduino LED tail light controller:
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