33. GDT for 24VDC Industrial Field Wiring Surge Protection

Tom is designing an industrial controller that receives 24VDC power from long field wiring running across a factory and outdoor cable trays. 

These long cable runs are exposed to lightning-induced surges and high-energy transients. 

He needs a GDT at the controller input as primary surge protection to absorb high-energy surges before they reach the downstream TVS diode and the board circuitry. 

Key requirements: 

• Field supply is 24VDC (can be up to 30V with tolerance) 

• GDT spark-over voltage: 75V (well above 30V max, fires only on surge) 

• Surge current: ≥5kA (8/20µs) for industrial lightning-class protection 

• 2-pole GDT (24V line and return) 

• Surface mount package for compact board layout 

The company's AVL specifies Littelfuse, so the part must be selected from Littelfuse on DigiKey. 

Help him select a suitable GDT from Littelfuse on DigiKey.