1500 W TVS Ratings: Pulse Energy and Protection Coordination
Understand 1500 W TVS ratings, calculate pulse energy from voltage and current, and check clamping, temperature, repetition and protection coordination.
Updated: October 28, 2026
This page is a focused engineering note in the tvs esd surge cluster—use the checklists and links below to finish selection, not as a substitute for the datasheet.
Topic hub: TVS diode selection guide. Related deep-dives sit in the continue list at the end.
| Before release | Pass criteria |
|---|---|
| Ratings vs mission profile | Voltage/current/thermal margins recorded |
| Package & PCB | Rth path agreed with layout |
| Docs | Datasheet rev + PCN policy filed |
| Alternates | At least one workable second source or risk accepted |
What the Class Actually Specifies
Read the class as a set of conditions, because the same nominal rating hides quite different test bases.
Bourns’ SMCJ series puts it at a minimum 1500 W peak pulse power dissipation on the non-repetitive 10/1000 µs waveform (the 1 ms width is the decay-to-half-current point), derated above a 25 °C ambient, in a DO-214AB (SMC) package covering 5.0 V to 495 V of standoff with breakdown to 550 V. STMicroelectronics’ SM15T series quotes 1500 W for a 10/1000 µs waveform and up to 10 kW for an 8/20 µs waveform, with 5.8 V to 188 V standoff entries in Table 2. Leakage is ordering-code-specific: SM15T12A/CA has a 0.2 µA maximum at its rated standoff and 25 °C, while SM15T6V8A/CA allows 500 µA under the corresponding condition. The family advertises up to 1250 W at maximum junction temperature; apply the exact test conditions and derating curves.
| Parameter | Bourns SMCJ | ST SM15T |
|---|---|---|
| Peak pulse power | 1500 W minimum on the specified 10/1000 µs non-repetitive waveform; 1 ms is its decay-to-half-current width | 1500 W at 10/1000 µs; up to 10 kW at 8/20 µs |
| Capability at maximum junction temperature | Derate above 25 °C ambient | Up to 1250 W at 150 °C |
| Standoff range | 5.0 V to 495 V | 5.8 V to 188 V in Table 2 |
| Forward surge current, distinct from avalanche clamp current | 200 A at 8.3 ms single half sine (unidirectional) | The cited table lists reverse-avalanche IPP for clamping; this is a different parameter from forward IFSM |
| Steady-state dissipation | 5.0 W at a 75 °C lead temperature | The 1500 W pulse rating is not a continuous-power rating |
| Leakage | Per part number at rated standoff | At rated standoff and 25 °C: SM15T12A/CA, 0.2 µA max; SM15T6V8A/CA, 500 µA max |
| Standards coverage stated | IEC 61000-4-2 (min level 4), IEC 61000-4-4, IEC 61000-4-5 | IEC 61000-4-2 above level 4 at 30 kV air and contact, IEC 61000-4-4 level 4 |
The Energy Arithmetic
Calculate energy from the device voltage and current over time: E = ∫vTVS(t)iTVS(t)dt. Peak power alone does not supply that integral.
- A constant 1500 W rectangular pulse lasting exactly 1 ms would dissipate 1.5 J. This is a mathematical example, not an SMCJ energy rating.
- The Bourns SMCJ pulse graph on page 4 defines its 1 ms width at half peak current, with a continuing tail. Use that waveform and the pulse-rating and temperature curves; do not replace it with a rectangular pulse.
- For load dump, TI SNOAAA1 explains that TVS energy depends on source voltage, clamp voltage, duration and source impedance. Its example 12 V Test A ranges are 79–101 V, 0.5–4 Ω and 40–400 ms. The absorbed energy is not a fixed value determined by those ranges alone.
For a simple resistive-source model, iTVS(t) ≈ max[(vsource(t) − vTVS(t))/Rsource, 0], assuming negligible load current and wiring inductance. This is an estimate, not a device guarantee. Include the real clamp characteristic, circuit dynamics and pulse train when validating a design. A 1500 W 10/1000 µs label alone establishes neither a pass nor a failure for a much longer load-dump event.
Coordination: the Part Nobody Reviews
A suppressor is one element of a chain, and the chain is what either survives or fails.
Work backwards from the protected node. The downstream circuit sets the maximum voltage it can tolerate; the suppressor’s clamping voltage at the actual surge current has to sit below that. The source impedance and the event duration set the current the suppressor must carry; the pulse power and derating curves decide whether it can. For a sustained fault, coordinate the fuse time-current curve and clearing I²t with the available fault current and the TVS failure behavior. A pulse-power rating is not a standalone fuse-clearing energy limit. Verify that normal transients do not cause nuisance opening. Where a central clamp already exists — an alternator-mounted suppressor in a vehicle, for example — the local device is sized for the residual, not for the full event.
That coordination is why industrial designs often look conservative on paper: the part is chosen for the residual energy after the upstream stage, not for the raw event. Where a supplier can provide derating curves, pulse definitions and qualification documents, that calculation can be checked rather than assumed.
Move from a pulse budget to a specific component
A pulse-power class does not identify a complete ordering code or guarantee that a given load-dump waveform is covered. After checking waveform, repetition, temperature, and protected-circuit limits, use the SMCJ device-selection guide to review a specific package and datasheet entry.
Release checklist
- Re-read absolute maximum ratings against worst-case spikes.
- Confirm pinout/package drawing matches the footprint library.
- Capture why this MPN beat the next alternative (loss, cost, lead time, or qualification).
Selection checklist before you freeze the MPN
- Confirm working voltage (VRWM) sits above the rail maximum including tolerance.
- Match surge waveform and peak pulse power (PPPM) to the threat—not only the catalog wattage label.
- Check clamping voltage at the expected surge current against IC absolute-max ratings.
- For high-speed lines, verify capacitance and whether unidirectional or bidirectional polarity fits the signal.
- Re-check derating curves at your board temperature; catalog PPPM is usually at 25 °C.
Ratings that decide real protection
| Parameter | What to verify | Why it matters |
|---|---|---|
| VRWM | Above max continuous voltage | Avoids leakage and false clamping in normal operation |
| VC @ IPP | Below protected IC abs-max | Clamping too high still destroys the load |
| PPPM / waveform | 8/20 µs vs 10/1000 µs as applicable | Watt labels are not interchangeable across pulses |
| Cj | Budget for USB/HDMI/RF integrity | Excess capacitance closes eyes on fast edges |
FAQ
Unidirectional or bidirectional TVS—how do I choose?
Use unidirectional on DC rails with a defined polarity; use bidirectional on AC or reversible/signal lines where either polarity can appear.
Does a higher wattage TVS always protect better?
No. Clamping voltage, waveform rating, and layout often matter more than the wattage label alone.
Where should the TVS sit on the PCB?
At the entry connector with a short return to the surge ground—long stubs raise inductive overshoot.
Continue through this engineering topic
- TVS diode selection guide
- What is a TVS diode
- 400 W vs 600 W Tvs Sizing the Pulse Energy
- 600w Tvs Protection Diode Reliable Circuit Protection for Power Electr
- Asmbj28ca 600 W Automotive Tvs in Smb for Lighting Drivers
- Choosing a Tvs for 24 V Inputs Industrial and Automotive
Topic hub: TVS diode selection guide — related selection guides and application notes in this cluster.