TVS Diode SMBJ / SMAJ / SMCJ – Quick Selection Guide

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When selecting a TVS (Transient Voltage Suppressor) diode, engineers usually start from three basic points: package type, peak pulse power and working voltage range. This quick guide focuses on three popular SMD options widely used in power supplies, chargers, LED drivers and industrial boards: SMAJ, SMBJ and SMCJ TVS diodes.

Use this page as a keyword-rich entrance and as a fast shortcut to detailed product pages, datasheets and application decisions.

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SMBJ / SMAJ / SMCJ – Quick Comparison Table

The table below summarizes the most commonly used TVS series in compact power designs. You can quickly compare package size, wattage and typical applications, then jump to the corresponding product page.

Series	Package	Peak Pulse Power	Voltage Range	Typical Uses	Product Page
SMAJ	SMA	400 W	5.0–440 V	Compact SMPS, telecom, adapter boards	View SMAJ TVS series
SMBJ	SMB	600 W	5.0–440 V	SMPS output lines, industrial control boards	View SMBJ TVS series
SMCJ	SMC	1500 W	5.0–440 V	High-power PSU, automation and industrial systems	View SMCJ TVS series

Extended TVS Options – Axial Series

For designs that prefer axial-leaded TVS diodes with higher surge capability or easier retrofit into existing layouts, the following series are frequently selected:

• 1.5KE Series – High surge 1500 W TVS for robust power lines
  Download 1.5KE datasheet
• P4KE Series – General-purpose 400 W transient suppressor
  Download P4KE datasheet
• P6KE Series – 600 W TVS for switching power supply protection
  Download P6KE datasheet
• SA5.0A Series – 500 W TVS for low-voltage signal and control lines
  Download SA5.0A datasheet

Voltage & Wattage Checklist

For quick decision-making, engineers often filter TVS diodes by wattage class first:

• 400 W class – SMAJ, P4KE
  Suitable for compact boards, adapters, telecom modules and low-to-medium surge levels.
• 600 W class – SMBJ, P6KE
  Used in SMPS outputs, industrial control, distribution boards and general-purpose protection.
• 1500 W class – SMCJ, 1.5KE
  Preferred for high-energy industrial lines, motor drives and harsh surge environments.

Within each series, voltage options typically span from 5.0 V up to 440 V, allowing engineers to match the TVS standoff voltage and clamping level to the system’s normal operating range.

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TVS Diode Basics – Reference Video

If you want a quick visual review of avalanche behavior, clamping voltage and surge waveforms, the following video is a helpful complement to this selection guide:

TVS Diode Basics & Surge Protection Explained

Use the video together with the comparison table above to align theory, waveforms and real-world part numbers from the SMAJ, SMBJ, SMCJ and axial TVS families.

Full TVS Diode Comparison – All Series

For detailed voltage lists, clamping curves, package drawings and complete selection across multiple series, visit the full Kingtronics TVS page:

Visit Full TVS Diode Comparison →

Engineering & Sales Support

Need help selecting the right TVS diode for your power supply, charger, LED driver or industrial controller? The Kingtronics team can assist with:

• Cross-reference from existing TVS part numbers
• Selection by surge level, package and voltage
• Recommendations for new projects and redesigns

Contact Kingtronics engineering & sales team →

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FAQ – TVS Diodes for Power Supplies & Industrial Electronics

1. What does a TVS diode do?

A TVS (Transient Voltage Suppressor) diode protects circuits from voltage spikes, ESD, and surge events. It clamps excessive voltage within nanoseconds to prevent damage to power supplies, chargers, LED drivers, and industrial equipment.

2. When should I use SMAJ, SMBJ or SMCJ?

Use SMAJ for compact 400W protection, SMBJ for 600W medium-surge power lines, and SMCJ for high-energy 1500W industrial and automation systems.

3. How do I choose the correct TVS standoff voltage?

Select a standoff voltage (V_RWM) slightly above the circuit’s normal operating voltage. This prevents unnecessary clamping and ensures reliable surge absorption.

4. What is clamping voltage in a TVS diode?

Clamping voltage is the maximum voltage the TVS allows during a surge event. Lower clamping voltage means better protection for sensitive ICs and power stages.

5. What TVS diode wattage is best for industrial electronics?

Industrial systems typically need 600W (SMBJ) or 1500W (SMCJ / 1.5KE) due to higher surge levels, inductive loads, and harsh electrical environments.

6. Are axial TVS diodes still used today?

Yes. Axial series such as P4KE, P6KE, 1.5KE, SA5.0A remain popular for retrofitting, high-energy surge paths, and designs requiring leaded components.

7. Can TVS diodes protect both AC and DC circuits?

Yes. Unidirectional parts are commonly used for DC rails, while bidirectional models protect AC lines, communication interfaces, and reversible power stages.

8. Where can I find all Kingtronics TVS part numbers?

All SMAJ, SMBJ, SMCJ, P4KE, P6KE, 1.5KE, and SA5.0A series are listed here:
Full TVS Diode Comparison →

Follow Kingtronics for More TVS Insights

For ongoing updates on TVS diodes, surge protection and circuit protection design tips, follow Kingtronics on LinkedIn:

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What Makes FKT-SA a Reliable Choice for Pulse and Snubber Circuits

Kingtronics International Company — Power Protection Expertise

In many high voltage and high frequency designs, the weak point is not the semiconductor, but the pulse capacitor or snubber capacitor sitting across it. Typical field issues include capacitors running hotter than expected, capacitance drift after repeated pulse cycles, unclear dv/dt capability, and difficulty reading derating curves in different operating conditions. When this happens, engineers often end up oversizing parts or adding extra margin “just in case”, which increases cost without necessarily solving the root cause.

Instead of starting from brand names, a more robust approach is to look at the underlying design: what does a high voltage film capacitor actually need to offer to survive in pulse and snubber circuits? Once those requirements are clear, it becomes much easier to check whether a given polypropylene film capacitor series really matches the application.

Typical Pain Points in Pulse and Snubber Capacitor Selection

In practice, engineers selecting a snubber capacitor or pulse capacitor often report similar pain points:

• The datasheet lists nominal voltage and capacitance, but gives limited guidance on how to interpret temperature derating and frequency behaviour in real power stages.
• It is not always obvious whether the capacitor’s construction is non-inductive and suitable for fast edges and high dv/dt.
• Dissipation factor and insulation resistance are given at one test frequency and temperature, while the actual application uses very different conditions.
• For long-life designs, engineers need to understand how high voltage film capacitors behave over thousands or millions of pulses, not just at a single test point.

These issues affect design choices in PFC stages, inverter legs, SCR commutation circuits, snubber networks, and electronic ballast or lamp driver circuits. The key question is always the same: how to map the datasheet parameters of an axial film capacitor to the actual stress in the application.

What Really Matters in a Pulse and Snubber Film Capacitor

When comparing different polypropylene film capacitor series for pulse or snubber use, engineers usually focus on a few core aspects rather than marketing descriptions:

• Dielectric and metallization: polypropylene is widely used thanks to its low loss and stable behaviour. Designs using double-sided metallization can support more demanding pulse conditions when correctly specified in the datasheet.
• Winding and inductance: a non-inductive film capacitor helps to control voltage overshoot and ringing in fast-switching, high dv/dt environments.
• Rated voltage vs. operating profile: simply matching the DC or AC rated voltage is not enough. Designers need to confirm how the usable voltage is derated with temperature and how this interacts with the circuit’s worst-case conditions.
• Dissipation factor and heating: a low dissipation factor at the relevant frequency reduces internal heating, which is important in high frequency capacitor positions.
• Insulation resistance and standards: parameters such as insulation resistance, climatic category and reference standards (for example, IEC 61071 capacitors for certain pulse applications) support a more objective comparison between different series.

Focusing on these points helps to narrow down candidate parts before any hardware build, which is especially useful when prototypes and qualification cycles are time-consuming.

Using Datasheet Curves Instead of Trial-and-Error

A common source of uncertainty is how to interpret graphs in the datasheet of a high voltage film capacitor. Curves of capacitance versus temperature, dissipation factor versus frequency, or insulation resistance versus temperature are often treated as “nice to have” rather than as hard design inputs. In pulse and snubber positions, however, these curves are exactly what show whether the device stays within its intended operating window.

By reading these charts alongside the rated values, a design engineer can estimate whether a given snubber capacitor or pulse capacitor is being used close to its specified limits or with an appropriate margin. This approach reduces dependency on trial-and-error and helps structure technical discussions between engineering, procurement and suppliers.

Example: Pulse and Snubber Film Capacitor in Practice

The short video below shows a practical example of a polypropylene axial film capacitor series used in pulse, snubber and high voltage applications. While every design has its own constraints, it can be helpful to see how a dedicated pulse/snubberseries is positioned and described at a high level.

Using the FKT Series Catalog as a Reference

For engineers who prefer to work directly from tables and curves, a consolidated film capacitor catalog is often more convenient than navigating multiple web pages. The FKT Series catalog groups together ratings, dimensions and ordering information for the family, including pulse-oriented options.

The following PDF provides a structured view of voltage ratings, capacitance ranges and mechanical formats within the FKT family:

Open FKT Series Catalog (PDF)

How FKT-SA Aligns with These Requirements

Within this context, the Kingtronics FKT-SA Series is specified as a double-sided metallized polypropylene axial film capacitor with non-inductive configuration. According to the datasheet, it is referenced to IEC 61071, with climatic category 40 / 105 / 56 and an operating temperature range from −40 °C to +105 °C. Rated voltages are listed at 250 V, 400 V, 630 V, 1000 V, 1600 V and 2000 V, and the available capacitance range extends from 0.00022 µF up to 3.9 µF.

The datasheet defines a dissipation factor ≤ 0.0010 at 1 kHz and 20 °C, and specifies insulation resistance values at 20 °C and 100 V for different capacitance ranges. It also provides guidance on voltage derating above the nominal temperature points for both DC and AC operation. For engineers comparing pulse capacitors or snubber capacitors, these parameters can be used directly in the usual selection process alongside other high voltage film capacitor options.

If you are currently reviewing pulse or snubber positions and need a documented, IEC-referenced polypropylene film capacitor series to compare against your design targets, you can:

View FKT-SA Specifications →

Contact Engineering / Sales →

Kingtronics® XKT MOV Series - Protecting Power Systems with Reliable Surge Clamping

Kingtronics International Company — Power Protection Expertise

Kingtronics® XKT MOV Series — Reliable Surge Clamping for Modern Power & LED Designs

XKT MOV series — fast, repeatable clamping against lightning and switching surges.

Stop damage from transient surges. The XKT Metal Oxide Varistor (MOV) Series clamps lightning- and switching-induced spikes within microseconds to keep SMPS, LED drivers, and industrial control boards operating safely and reliably.

Quick Selection — Match Disc Size to Use Case

5D I/O, control lines, modest surges
7D General SMPS inputs, consumer power
10D Adapters, LED drivers with higher surge risk
14D Industrial modules, motor/relay suppression
20D Heavy-duty mains, severe surge environments

Key Advantages for Design Engineers

• Wide operating voltage: 18 V to 1800 V covers low-voltage rails up to AC mains.
• Multiple disc sizes: 5D, 7D, 10D, 14D, 20D options scale surge capability and footprint.
• High surge endurance: 20D series up to 6,500 A (8/20 µs) and 606 J (10/1000 µs) on top variants.
• Compliance: RoHS & REACH compliant for global deployments.

Specs Snapshot — Proven by Data

Example XKT20D162K: Varistor Voltage ≈ 1600 V (±10%), Max Energy 606 J (10/1000 µs), Peak Current 6,500 A (8/20 µs).

Where XKT MOVs Excel

Ideal for AC/DC power supplies, LED lighting, telecom rails, and industrial automation. Broad voltage coverage supports both 110 V and 220 V regions; size options let you trade off footprint vs. surge capability for cost-effective protection.

XKT portfolio from 5D to 20D — choose footprint vs. surge capability for your design.

Environmental Compliance & Quality

Every XKT MOV is RoHS & REACH compliant and validated through electrical, surge, and thermal checks for long-term reliability in real applications.

FAQs: Selecting & Applying XKT MOVs

How do I choose the right XKT MOV voltage?

Pick V_1mA so the MOV stays non-conductive at nominal line but clamps below the protected device’s absolute maximum. The XKT portfolio spans 18–1800 V to cover low-voltage rails through AC mains.

When should I step up from 10D to 14D or 20D?

Move to larger discs when surge tests (e.g., IEC 61000-4-5) require higher peak current or energy. 14D/20D provide substantial headroom; 20D handles up to 6,500 A and ~606 J on top variants.

Are XKT MOVs certified for environmental regulations?

Yes. The full series is RoHS and REACH compliant.

Explore the complete Kingtronics XKT MOV Series and find the optimal clamping device for your next design.

Explore XKT Series

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