31. TVS Diode for 3.3V GPIO ESD Protection
1. Component Purpose
MCU GPIO pins connected to external connectors are exposed to ESD during cable assembly and field maintenance. A bidirectional TVS on each exposed line clamps ESD to a safe level.
This is similar to the USB ESD task, but capacitance is relaxed to ≤50pF because general GPIO signals are much slower than USB data. Standoff of 5–6.5V is well above the 3.3V GPIO HIGH level.
Required: Bidirectional · Vstandoff 5–6.5V · Vclamp ≤20V · ≤50pF · SOD-323 · Littelfuse
2. How to Find It on DigiKey
Go to DigiKey.com → Circuit Protection → TVS - TVS Diodes
Apply these filters:
- Bidirectional Channels → 1
- Voltage - Reverse Standoff (Typ) → 5V to 6.5V range
- Capacitance → 50pF or lower
- Package / Case → SOD-323
- Manufacturer → Littelfuse Inc.
- Part Status → Active
Tip: Unlike USB data lines (≤5pF required), general GPIO can tolerate higher TVS capacitance. This gives you more part options and lower cost.
3. Key Specifications & What They Mean
| Specification | Required | Why |
|---|---|---|
| Direction | Bidirectional | ESD strikes in both polarities. |
| Standoff Voltage | 5–6.5V | Well above 3.3V GPIO logic level. |
| Clamping Voltage | ≤20V | Brief ESD pulse; MCU survives. |
| Capacitance | ≤50pF | Acceptable for general GPIO speeds. |
| Package | SOD-323 | Compact; near connector pins. |
| Manufacturer | Littelfuse | Company AVL. |
| 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