Short Circuit Spring Plastic Foil
Ceramic Tube
Outer Electrode
Center Electrode
Fail-Short Mechanism — FT
Short Circuit Spring Solder Pellet
Ceramic Tube
Center Electrode
Outer Electrode
Fail-Short Mechanism — FS
Operation and Storage Temperatures for Gas Discharge Tubes
Fail-Short Mechanism for Gas Discharge Tubes
Operation Temperature Range Storage Temperature Range
Models without Fail-Short Mechanism : -40°C/+90°C Models without Fail-Short Mechanism : -40°C/+90°C
Models with Fail-Short Mechanism : -20°C/+65°C Models with Fail-Short Mechanism : -20°C/+65°C
Figure G12
Figure G13
The FS fail-short mechanism is a short circuit spring mounted onto a solder pellet located
at the center electrode of the gas tube. Under normal operating conditions, the pellet is
positioned to make the spring float above the outer electrodes, as shown in Figure G11 on
the previous page..
When a prolonged discharge event causes the gas tube temperature to reach the melting
point of the solder, the pellet softens allowing the short circuit spring to contact with both
outer electrodes (Figure G12). This process results in a permanent short circuit between all
three electrodes creating a low resistance path that conducts the fault current to ground
without generating a significant amount of heat.
The FT fail-short mechanism is a short circuit spring with a piece of plastic foil spot welded
onto the center electrode. Under normal operating conditions, the plastic foil makes the
spring insulated from the two outer electrodes.
When a prolonged discharge event causes the gas tube temperature to reach the melting
point of the plastic foil, the plastic foil melts allowing the short circuit spring to contact both
outer electrodes (Figure G13). This process results in a permanent short circuit between all
three electrodes creating a low resistance path that conducts the fault current to ground
without generating a significant amount of heat.
Packaging Information for Gas Discharge Tubes
Parts in Bulk Parts in Tape and Reel
Min Order Box Tape and Reel Box
Part Description Quantity Quantity Min Order Quantity Quantity
3mm 2Pole Surface-mount — — 2000 16000
5mm 2Pole No leads 5000 20000 — —
5mm 2Pole Leads 1000 5000 — —
5mm 2Pole Surface-mount — — 1500 12000
6mm 2Pole No leads 2000 10000 — —
6mm 2Pole Leads 1000 5000 — —
6mm 2Pole Surface-mount — — 750 6000
8mm 2pole No leads 2000 10000 — —
8mm 2Pole Leads 1000 5000 — —
8mm 2Pole Surface-mount — — 500 4000
5mm 3Pole No leads 2500 10000 — —
5mm 3Pole Leads 1000 5000 — —
5mm 3Pole Surface-mount — — 1000 8000
6mm 3Pole No leads 2500 10000 — —
6mm 3Pole Leads 1000 5000 — —
6mm 3Pole Surface-mount — — 750 4500
7mm 3Pole Leads 1000 5000 — —
8mm 3Pole No leads 1000 5000 — —
8mm 3Pole Leads 1000 5000 — —
8mm 3Pole Surface-mount — — 500 2500
RoHS Compliant, ELV Compliant Specifications subject to change without notice. ©2016 Littelfuse, Inc. 81
Gas Discharge Tubes (GDTs)