Low-noise 12V to 5V conversion

[Derek Morrison]

Dear Forum:

Does anyone have ideas on the lowest-noise solution to get 12V down to 5V?  I have a FlexRadio and an SDR/Raspberry Pi monitoring UHF in my attic.  I recently changed back to a linear power supply and am trying to get rid of some wall warts.  The Raspberry Pi runs on 5V/2.5A.

Thank you!

[Burns FISHER]

Are you talking about homebrew?  An LDO regulator (not a switching one).

 

 

[Nashua Area Radio Society]

Don’t know if its considered “low noise,” but I’m betting this one would be quieter than a wall-wart:

https://www.adafruit.com/product/1385

I’ve also got myself a bunch of smaller buck converters, but the link above is good for up to 3A output at 5V.

[Nashua Area Radio Society]

If you want an off-the-shelf solution, it would be a DC-DC converter module. They’re available from major electronics distributors such as Digi-Key and Mouser. They’re usually small rectangular modules with pins meant for a PC board, so you’d mount yours in your equipment with double-sided tape, and solder wires on.
The ripple at the switching frequency might be higher than you want, but an LC pi filter downstream can attenuate it to a millivolt peak-to-peak or less, at the cost of degraded transient response.
Caution: download the PDF data sheet before selecting the module you want, and read it carefully. Some DC-DC modules require external components for stability or ripple reduction. I would usually install a transient voltage suppressor across the input, to prevent resonant overcharging due to the inductance of the lead wires when plugging into a live voltage source.

Jack Carroll W1PK

[Author]

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