Putting together a circuit board to be used in an automobile

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    I’m looking at putting together a circuit board to be used in an automobile. It will only be connected to a 12 V and ground. Everything else will be internal to my board.

    I was planning on putting a 12 V regulator up front to make sure I could rely on clean power for my design and found a few that seem to be rated for cars. While looking for regulators I stumbled on automotive grade regulators.

    Here is one from Digikey: 12 V – 497-10192-1-ND (LD1086DTTRY:http://www.kynix.com/Parts/265567/LD1086DTTRY.html , IC REG LDO ADJ 1.5A DPAK, -40°C ~ 125°C)

    I know that they’re designed to protect the downstream circuit from possible voltage dumps (or surges) from all the electrical noise found in a car.

    Anyway this brought up a whole set of questions, but the main one was this: As long as any external connections between the electrical system and my board are bridged with automotive grade components (and I stay out of extreme climate areas found in/around cars) can I just use regular off the shelf components?

    Or do I need to find automotive grade for everything?

    For example, if I’m trying to use this circuit:


    Can I just use an automotive grade for the upstream regulator (IC1) and an regular grade part for the downstream 5 V regulator (IC2)?

    I’ll try to add some details for clarity. I want to run a small 12 V device and was planning on running a current divider to the microchip so I don’t run the device if I ever have less than 12 V.

    The rough current requirements are as follows: – 12 V @ .833 A – 5 V @ .05 A – 3.3 V @ .15-.20 A

    I was debating getting an automotive grade LDO and then using regular LDO’s after that on the back end for the other devices.

    This is a one off project currently but if it works I think I could build up a few and sell them down the road. So I’d rather do it correctly the first time and hopefully get a good design.


    I think we need to analyse and inquire in detail before we go with investments.

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