SMCJ TVS Diodes: Package, Clamping and Device Selection
SMCJ is not a rating but a class: a 1500 W transient voltage suppressor in a DO-214AB (SMC) body. Bourns’ series covers 5.0 V to 495 V of standoff, a 200 A.
Updated: October 28, 2026
SMCJ is not a rating but a class: a 1500 W transient voltage suppressor in a DO-214AB (SMC) body. Bourns’ series covers 5.0 V to 495 V of standoff, a 200 A peak forward surge current and 5 W of steady-state dissipation at a 75 °C lead temperature, and those three numbers, not the headline figure, are what tell you whether it fits a design.
Reading the 1500 W Rating Correctly
A peak pulse power rating is meaningless without its waveform, and the SMCJ class is a good place to see why.
Bourns’ SMCJ data sheet states 1500 W minimum peak pulse power dissipation at a 1 ms pulse, with the note that the value is non-repetitive and must be derated above a 25 °C ambient. ST’s SM15T — the same 1500 W class from another vendor — quotes 1500 W for a 10/1000 µs waveform, up to 10 kW for an 8/20 µs waveform, and states plainly that capability falls to about 1250 W at its 150 °C maximum junction temperature.
Those three statements are consistent, and together they describe the shape of a TVS: the shorter and steeper the pulse, the more power the die can take; the hotter the junction, the less it can take. A selection made from the headline number alone therefore assumes the mildest condition in the datasheet.
| Parameter | Bourns SMCJ series | ST SM15T series |
|---|---|---|
| Peak pulse power | 1500 W minimum at TP = 1 ms | 1500 W at 10/1000 µs; up to 10 kW at 8/20 µs |
| Standoff voltage range | 5.0 V to 495 V (breakdown to 550 V) | 5 V to 188 V |
| Surge current | 200 A (8.3 ms single half sine, unidirectional) | Per part number at the rated pulse |
| Steady-state dissipation | 5.0 W at TL = 75 °C | Not specified as a DC rating |
| Forward voltage at IPP = 100 A | 3.5 V (5.0 V to 90 V parts), 5.0 V (100 V to 495 V parts) | Per part number |
| Leakage | Per part number at rated standoff | 0.2 µA at 25 °C |
| Junction temperature | −55 °C to +150 °C | 150 °C maximum |
| Package | DO-214AB (SMC) | SMC |
Selecting One, in Order
Four steps, and each one can eliminate a part number before the next matters. Set the standoff above the highest normal operating voltage including tolerance, so the device stays off in service. Then take the clamping voltage at the peak pulse current the circuit can present and check it against the absolute maximum of everything downstream. Then compare the pulse energy with the class rating above. Finally, confirm the mechanical and qualification details: the SMC body, the unidirectional or bidirectional configuration, and — for automotive programmes — an AEC-Q101 qualified variant such as the HE3 or HM3 ordering codes on the Vishay SMBJ series, or the equivalent qualification route from other vendors.
The reverse of that order is where projects get stuck: choosing by the 1500 W headline and discovering at validation that the clamping voltage at the real surge current sits above the supply’s absolute maximum, or that the energy is two orders of magnitude beyond the class.
Check the package and clamping entry together
For an SMCJ candidate, confirm its package outline, polarity suffix, maximum operating rail voltage, and clamping result at the stated test current. A power-class label does not establish the protected circuit’s margin. Use the 1500 W pulse-energy guide for the separate waveform and protection-coordination discussion.
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.
SMAJ vs SMBJ vs SMCJ—what actually changes?
Mainly package size and peak pulse power capability; still match VRWM, clamp, and waveform to the threat.
Related Articles
- What makes an SMBJ TVS diode the right choice?
- What is a low clamping voltage TVS?
- How do TVS diodes solve automotive load dump issues?
- Bidirectional surge protection diodes
- Talk to a Good-Ark engineer
Official Resources
References
- Bourns, SMCJ Transient Voltage Suppressor Diode Series — source of the 1500 W minimum peak pulse power at 1 ms, the 5.0 V to 495 V standoff range with breakdown to 550 V, the 200 A 8.3 ms surge current, 5.0 W steady-state dissipation at a 75 °C lead temperature, the forward voltages at 100 A, the −55 °C to +150 °C range and the DO-214AB (SMC) package. bourns.com — SMCJ series datasheet (PDF)
- STMicroelectronics, SM15TxxA, SM15TxxCA — 1500 W TVS in SMC — source of the 1500 W (10/1000 µs) and up to 10 kW (8/20 µs) ratings, the 5 V to 188 V standoff range, 0.2 µA leakage, 1250 W at maximum junction temperature and the 150 °C limit. st.com — SM15T series datasheet (PDF)
- Vishay, SMBJ5.0A thru SMBJ188A, document 88392 — the 600 W class used for the SMBJ-versus-SMCJ comparison, including the AEC-Q101 ordering codes. vishay.com — SMBJ datasheet (PDF)
- Texas Instruments, Protection against Unsuppressed Load Dump in Automotive Systems, SNOAAA1 — source of the ISO 16750-2 test A pulse parameters (79 V to 101 V, 0.5 Ω to 4 Ω, 40 ms to 400 ms for a 12 V system) used in the energy comparison. ti.com — unsuppressed load dump application brief (PDF)
Continue through this engineering topic
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- What is a TVS diode
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- 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
Topic hub: TVS diode selection guide — related selection guides and application notes in this cluster.