Reverse Polarity Protection Diode

Question

Problem: Reverse Polarity Protection Diode. Solve this hands-on electronics task on EWskills.

Accepted Answer

1. Component Purpose

If someone accidentally connects the 12V power supply backwards, the reversed voltage can instantly destroy ICs and other sensitive components on the board.

A series Schottky diode on the input line blocks current when polarity is reversed (diode is reverse-biased), protecting the entire board. A Schottky type is chosen instead of a standard diode because it has a much lower forward voltage drop (≤0.5V vs ~0.7V for standard), meaning less wasted power during normal operation.

Required: Schottky · ≥1A · ≥30V · Vf ≤0.5V · SMA · SMD · −40°C to +125°C · RoHS

2. How to Find It on DigiKey

Go to DigiKey.com → Discrete Semiconductor Products → Diodes - Rectifiers - Single

Apply these filters:

Diode Type (Technology) → Schottky
Voltage - DC Reverse (Vr) → 30V or higher
Current - Average Rectified (Io) → 1A or higher
Voltage - Forward (Vf) → Check datasheet for ≤0.5V
Supplier Device Package → SMA (DO-214AC)
Part Status → Active

Tip: DigiKey lists Vf at a specific test current (usually the rated current). Make sure Vf ≤0.5V at the test current shown, not just at very low current.

3. Key Specifications & What They Mean

Specification	Required	Why
Diode Type	Schottky	Low Vf; minimizes voltage loss in series path.
Avg Current (Io)	≥1A	Board draws 500mA; 2× margin for safety.
Reverse Voltage (Vr)	≥30V	Must block full 12V reverse with margin.
Forward Voltage (Vf)	≤0.5V	Keeps power loss low during normal use.
Package	SMA	Standard SMD package for this current level.
Temp Range	−40°C to +125°C	Industrial operating conditions.
RoHS	Yes	Compliance required.

4. Selecting a Safe, Production-Ready Part

The filtered list will show many matching parts. Before you pick one, check: Is it Active? Is stock available? Is the manufacturer reputable? Is a datasheet available?

Full checklist: How to Select a Safe, Production-Ready Component — EWskills Guide

5. Filtered DigiKey Link

➡ View Matching Parts — Schottky, SMA, ≥1A, ≥30V, Vf ≤0.5V

29. Reverse Polarity Protection Diode