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I'd like to put a small gadget that I made into my car and power it from the car battery. The gadget works on 12 volts and the car provides 12 volts also. And the consumption would be somewhere around 2-4A. However as I understand those 12 volts from the car are not very stable and can have short spikes up to 60 volts. Which would be a problem for my board.

Could you recommend a good way to stabilize those 12 volts from the car? I'm wondering between maybe buck converter, linear stabilizer and overvoltage protection.

Thanks!

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    \$\begingroup\$ You'll also have to deal with undervoltage lock out caused when the voltage on the battery is sagging down to 6V for things like engine-startup. There are automotive DC-DC supplies designed for the very task of dealing with this voltage swinging from the alternator and starter. \$\endgroup\$
    – Dave
    Feb 2, 2016 at 12:47
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    \$\begingroup\$ Also, I believe, that when the car is running and the Alternator is spinning the system voltage will be around 14.2v. \$\endgroup\$
    – Tyler
    Feb 2, 2016 at 13:07
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    \$\begingroup\$ Pick a switcher which is able to output 2-4A and you are ready to go.digikey.com/product-search/en/integrated-circuits-ics/… \$\endgroup\$
    – lucas92
    Feb 2, 2016 at 15:15
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    \$\begingroup\$ Yes it would be enough, step-down regulators output voltage is from 0V to Vin. See the LTC3414: cds.linear.com/docs/en/datasheet/3414fb.pdf \$\endgroup\$
    – lucas92
    Feb 2, 2016 at 15:27
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    \$\begingroup\$ The LM2576 seems to not be able to output voltage equal to Vin so you were right. The LTC3414 does the job though, and you can simulate it using LTSpice. \$\endgroup\$
    – lucas92
    Feb 2, 2016 at 15:32

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I think the linear stabilizer will be acceptable solution, if your gadget may eat lower voltage than 12V (about 10% lower). If yes, then you may use LM-338 for example. This stability margin (10%) is needed because the every linear stabilizer has its own voltage drop near 1V or higher. And, of cause, follow the recommendations regarding capacitors - their capacity must be enough for expected load, and their voltage must be 50-60V at least to respect your remark about real voltage pikes. If your gadget is pretty simple and has some resistance to voltage overload, then you may use only LC-filter based on ferrite-ring and a combination of big capacitor and ceramic capacitor (purpose of second one is to eat the noise of generator's rectifier and ignition of brushes). If the voltage precision is a key, then your choice is a double convert 12 to ~220 and then ~220 to 12, by using a car power adapter (inverter). These adapter should be able to give you much more than 2-4 Amps.

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