29. TVS Diode for 24VDC Industrial Input Protection
1. Component Purpose
Industrial 24VDC bus lines pick up fast transient spikes from motors, solenoids, and contactors. A unidirectional TVS diode across the power input clamps these spikes to a safe level.
Standoff voltage of 27–30V is above normal bus voltage (24V +10% = 26.4V) but ensures clamping stays ≤50V to protect downstream components.
Required: Unidirectional · Vstandoff 27–30V · Vclamp ≤50V · ≥400W · SMA · Littelfuse
2. How to Find It on DigiKey
Go to DigiKey.com → Circuit Protection → TVS - TVS Diodes
Apply these filters:
- Unidirectional Channels → 1
- Voltage - Reverse Standoff (Typ) → 27V to 30V range
- Power - Peak Pulse → 400W or higher
- Package / Case → SMA
- Manufacturer → Littelfuse Inc.
- Part Status → Active
Tip: Unidirectional TVS is correct for DC power rails — it clamps positive surges and conducts like a normal diode in reverse. Bidirectional would waste headroom on the unused polarity.
3. Key Specifications & What They Mean
| Specification | Required | Why |
|---|---|---|
| Direction | Unidirectional | DC rail; single-polarity surges. |
| Standoff Voltage | 27–30V | Above 24V+10%; below 50V clamp limit. |
| Clamping Voltage | ≤50V | Protects downstream 50V-rated parts. |
| Peak Pulse Power | ≥400W | Industrial surge levels. |
| Package | SMA | Standard power TVS package. |
| Manufacturer | Littelfuse | Company AVL requirement. |
| Temp Range | −55°C to +125°C | Industrial conditions. |
| 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