Protection
TSS (Thyristor Surge Suppressor)
Crowbar-style surge protectors for telecom and high-energy line protection.
What is it?
A TSS (Thyristor Surge Suppressor, sometimes called SIDACtor or surge thyristor) is a PNPN structure that, when triggered by an over-voltage event, snaps into a low-impedance crowbar state. Unlike a TVS that clamps to a fixed clamping voltage, a TSS pulls down to ~3 V holding voltage and shunts very high currents (tens to hundreds of amps) with minimal heating. Used where the surge energy is too high for a clamping TVS to absorb.
When do you need it?
- Telecom subscriber-line interfaces (POTS, xDSL, ISDN) facing lightning-induced surges.
- Industrial Ethernet (10/100/1G) with long outdoor cable runs.
- Power-line communication interfaces.
- Any system that must survive multi-kA surges per ITU-T K.20 / K.21 / GR-1089.
How to pick the right one
- VBR (Breakdown Voltage)
- Above maximum normal line voltage. Telecom POTS uses ~190-265 V (high-voltage TSS).
- IH (Holding Current)
- Below the maximum normal line current. Otherwise the TSS won't reset after triggering.
- ITSP (Peak Pulse Surge Current)
- Must exceed the lightning surge rating you need to pass — typically 100 A to 1 kA for telecom.
- Symmetric vs Asymmetric
- Telecom POTS uses symmetric (line swings positive and negative); some industrial uses asymmetric.
What Magnias offers
Magnias provides TSS devices for telecom and industrial line protection, in both single-port and two-port configurations. Most parts target the standard 220/270/350 V telecom thresholds.
Common questions
How is TSS different from a TVS?
A TVS clamps (acts like a Zener). A TSS crowbars (snaps to a low-voltage held state). TSS handles much higher surge energy because almost no power is dissipated in the device once it triggers.
Will a TSS work for ESD protection?
No — TSS trigger speed is microseconds, ESD events are nanoseconds. Pair TSS (for big surges) with a fast ESD diode (for fast transients) — common in telecom front-ends.
Why does TSS need to reset?
After triggering, the TSS holds in low-Z state while load current exceeds IH. When normal line current drops below IH (e.g., on the next ring cycle for telecom), the TSS resets. You need to verify IH is below your minimum normal current.