The Semiconductor discharge tube (TSS) is a surge protection device based on the Thyristor structure, mainly used for overvoltage protection. It features rapid response, high surge absorption capacity and self-recovery characteristics.
l Basic structure: Similar to A thyristor (PNPN four-layer structure), with anode (A), cathode (K), and gate (G) (some models have no gate).
l Trigger mechanism:
¢ When the voltage exceeds the breakdown voltage (V_{BR}), the TSS conducts rapidly (similar to "avalanche breakdown").
¢ After conduction, it presents a low impedance that can drain the amplified current (similar to GDT, but based on semiconductor process).
¢ When the current is lower than the holding current (I_H), it automatically turns off and returns to the high resistance state.
Features:
l Voltage clamping: More precise than GDT, suitable for protecting sensitive circuits.
l Fast response (ns level), but slightly slower than TVS.
l Self-recovery, no life loss issues (superior to MOV).
Parameters | Instructions | Typical values |
Breakdown voltage (V_{BR}) | The voltage at which TSS triggers conduction | 6V ~ 600V |
Clamping voltage (V_{CL}) | Voltage drop after conduction | Lower than V_{BR} |
Peak pulse current (I_{PP}) | Maximum surge current that can be tolerated | Tens to hundreds of A |
Maintenance current (I_H) | The minimum current to maintain conduction | A few mA to tens of mA |
Capacitor (C) | Affecting high frequency signals | Tens to hundreds of pF |
Characteristics | TSS | GDT | MOV | TVS |
How it Works | Semiconductor (Thyristor) | Gas discharge | Varistor | Diode avalanche |
Response time | Nanosecond level | Nanoseconds | Nanoseconds | Picosecond level |
Clamping ability | Better | Difference (low voltage after conduction) | General | Best |
Flow capacity | Medium (tens of A) | High (kA grade) | High (kA) | Low (hundreds A) |
Self-recovery | is | is | No (may be damaged) | is |
Lifespan | long | Limited (gas consumption) | Limited (aging) | long |
Applicable scenarios | Communication, data line | High voltage lightning protection | Power surge protection | Precision circuits |
l TSS is used for differential mode protection against damage to the chip by lightning or ESD.
l Sample circuit:
1 Signal line → [TSS] → [TVS] → Chip
¢ TSS drains the amplification current, TVS provides fine clamping.
l Suitable for low-voltage DC power supply (e.g. 24V industrial power supply).
l Combined MOV or GDT use:
1 Power input → [GDT] → [TSS] → Subsequent circuit
l Choose a low-capacitance TSS (e.g. <10pF) to avoid signal attenuation.
1. Breakdown voltage (V_{BR}) : higher than the operating voltage (e.g. 6V~10V TSS for a 5V circuit).
2. Peak current (I_{PP}) : According to the surge grade (e.g. IEC 61000-4-5 standard).
3. Package: SMD (e.g. SOD-323), through-hole (e.g. DO-214), etc.
4. Unipolar/Bipolar:
¢ Unipolar TSS: Only effective against positive or negative surges.
¢ Bipolar TSS (e.g. Pxxx0S series) : Protects against both positive and negative surges.
l TSS advantages: Self-recovery, quick response, suitable for low-voltage precision protection.
l Applicable scenarios: communications, data lines, DC power ports.
l Pairing recommendations:
¢ High frequency signal: TSS + low capacitance TVS.
¢ High energy surge: TSS + GDT/MOV (multi-level protection).
If specific circuit design or model recommendation is needed, application scenarios (such as voltage, surge level, etc.) can be provided!
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