39. GPIO Status LED Selection
1. Component Purpose
A status LED connected directly to a 3.3V GPIO shows system states like heartbeat, fault, or ON. The key constraint is that most MCU GPIO pins can only source 4–20mA. The LED must be bright enough at low current (≤5mA) to remain visible.
A 0603 SMD LED is tiny and saves board space — ideal for a small MCU board where multiple status LEDs may be needed.
Required: Green · 0603 · SMD · Vf 2.0–3.4V · ≤5mA test current · ≥10mcd · −40°C to +85°C · RoHS
2. How to Find It on DigiKey
Go to DigiKey.com → Optoelectronics → LED Indication - Discrete
Apply these filters:
- Color → Green
- Package / Case → 0603 (1608 Metric)
- Mounting Type → Surface Mount
- Part Status → Active
Then check each part’s datasheet for:
• Test current ≤5mA and luminous intensity ≥10mcd at that current
Tip: Not all LEDs are efficient at low current. Look for "high-efficiency" or "low-current" LEDs specifically designed to be bright at 2–5mA. Standard LEDs rated at 20mA may be barely visible at 5mA.
3. Key Specifications & What They Mean
| Specification | Required | Why |
|---|---|---|
| Color | Green | Standard status indication color. |
| Package | 0603 | Space-saving for small MCU boards. |
| Forward Voltage | 2.0V to 3.4V | Must work within 3.3V GPIO headroom. |
| Test Current | ≤5mA | GPIO pin current limit. |
| Luminous Intensity | ≥10mcd at low current | Must be visible despite low drive. |
| Temp Range | −40°C to +85°C | Standard industrial range. |
| RoHS | Yes | Compliance required. |
4. Selecting a Safe, Production-Ready Part
The filtered list will show 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