This is a placeholder topic for “Pololu 3.3V, 2.6A Step-Down Voltage Regulator D24V22F3” comments.
This small synchronous switching step-down (or buck) regulator takes an input voltage from 4 V to 36 V and efficiently reduces it to 3.3 V. The board…
Read moreFrom the product description:
“The modules have built-in reverse-voltage protection”
What is that referring to? A diode?
What would happen If I wired it wrong?
I’m using this in a power supply and I’m deciding if I need a external diode or if I can trust the board?
I’ve got multiple of these, so there is a chance that I get lazy and accidentally connect the Regulator A’s 3v3 out to Regulator B’s 5v out.
Hey @Pixmusix,
On the D24V22Fx series, the reverse‑voltage protection applies to the VIN input. Its job is to save the regulator if +VIN and GND are accidentally swapped. This is usually done with either:
Pololu often uses the MOSFET method, so chances are good it’s that. In short, if VIN is reversed, the board won’t power up but it also won’t be damaged.
Thanks to the built‑in protection, nothing catastrophic, the regulator will just sit idle instead of frying. Without such protection, most switching ICs would be destroyed by reverse polarity.
That’s a different situation. The input protection doesn’t cover outputs. If you tie a 3.3 V rail directly to a 5 V rail, the higher voltage can backfeed into the lower regulator’s internals (through MOSFETs and control circuitry). That can easily damage the board.
So that we can now circle back to this point
You can rely on the built‑in protection for the input side. But for output‑to‑output mishaps, the module won’t protect itself. If you want insurance against accidental cross‑connections, consider adding a Schottky diode in series (though this gives ~0.2 V drop) to make an "OR"ing circuit. Alternatively, good labeling or keyed connectors can save you from the problem without adding parts or losing efficiency.
This is the way. 
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