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I need to convert 12 V down to 5 V and 3.3 V.

I am using linear regulators right now but they get pretty warm and eventually I would like to supply more current for it (around 500-700 mA).

If I used a buck converter to get the voltage down to 5 V, then also feed the 5 V into the 3.3 V linear regulator is that acceptable? Assuming the buck converter can handle the current of the 5 V components and the 3.3 V ones? Also, this would cut down on heat from the linear regulator, correct?

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The only drawback is loss of efficiency if any. Depends on how efficient a 12 to 3.3V linear regulator would be or a 5v to 3.3v switching regulator would be. Otherwise, a linear regulator typically tends to smooth and is less noisy than a switching reg, and has less complicated layout requirements. Everything is a trade off, but 5V to 3.3V is often done with ldo instead of switching regs for noise abatement reasons

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  • \$\begingroup\$ Ok thanks , just wanted to make sure there wasn't something where the two don't mix. I'm fine with an efficiency loss \$\endgroup\$ – Tom Sep 11 '18 at 1:22
  • \$\begingroup\$ They compliment each other. It's all a cost benefit analysis. \$\endgroup\$ – Passerby Sep 11 '18 at 1:39
  • \$\begingroup\$ @Tom you could also go with a tighter compromise if you wish to have the benefit of both worlds, buck down to 3.5V and chop off .2V (and all of the ripple) with the LDO. \$\endgroup\$ – K H Sep 12 '18 at 2:47
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The downside is power losses .The linear will waste some power .When you go from 5 to 3V3 you can expect the linear reg to be 66% efficient .If your buck converter is 90% efficient your overall efficiency would be about 60% .This downside is relevant at high power.

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