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I'm designing a simple PCB that will control some sensors/actuators with a microcontroller.

The microcontroller requires 3.3V and I'm planning to support different types of sensors/actuators that can require either 5V or 12V supplies, but all have 5V logic level.

3.3V: Easy, a step-down converter that accepts anywhere from 5V to 12V.

5V for the logic shifter: I could do the same as with 3.3V, but what if the power supply itself is 5v?

I've opened up a cheap LED strip controller I had laying around, one that supports any power brick from 5V to 24V. That controller has a buck converter for 3.3V and what seems to be an LDO (I can't read the part number,) bringing the 3.3V up to 5V for the logic shifter.

I could do the same, but that seems like a waste of energy so I was wondering if there is a better way to go about this.

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    \$\begingroup\$ An LDO can't bring 3v3 back up to 5. Could a buck-boost work for your case? \$\endgroup\$
    – nanofarad
    Jan 5, 2022 at 17:08
  • \$\begingroup\$ Right, so what I thought to be an LDO, must be another buck converter. Interesting \$\endgroup\$
    – Cyborgium
    Jan 5, 2022 at 18:11
  • \$\begingroup\$ A buck converter also cannot bring a voltage up. A boost converter may, a charge pump may, but a buck converter by design bucks (lowers) a voltage. \$\endgroup\$
    – nanofarad
    Jan 5, 2022 at 18:12

1 Answer 1

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5v for the logic shifter: I could do the same as with 3.3v, but what if the power supply itself is 5v? I was wondering if there is a better way to go about this.

I'd consider using a buck-boost converter. An example: -

enter image description here

If you need more than 1.5 amps, there are others to choose from. Other products made by TI will also do the job. The point I'm making is this: use a buck-boost regulator. ADI also provide this device for a 1 amp output: -

enter image description here

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