Can 8/20 μs and 10/1000 μs TVS Ratings Be Compared Directly?

ASIM Technical Team · Published 2026-09-20

TVS ratings measured with 8/20 μs and 10/1000 μs pulses cannot be ranked from IPP, VC, or PPPM alone. The waveform is part of the rating. A defensible comparison keeps the full part number, pulse waveform, peak current, clamping-voltage operating point, temperature, repetition condition, package, and data-sheet revision together. There is no universal conversion factor that turns every 10/1000 μs rating into an equivalent 8/20 μs rating.

The waveform is part of IPP and peak-pulse-power data

ROHM Application Note No. 66AN047C, Rev.001, states that a TVS data sheet may specify peak pulse current IPP with either the 10/1000 μs waveform associated with Telcordia GR-1089-CORE or the 8/20 μs waveform used in IEC 61000-4-5. The same note ties the peak pulse power specification to the corresponding current waveform.

That distinction prevents a common data-normalization error. If device A lists a larger IPP under 8/20 μs and device B lists a smaller IPP under 10/1000 μs, the larger number does not establish a stronger device. The longer pulse and the shorter pulse create different current-duration and thermal conditions.

The labels 8/20 μs and 10/1000 μs are standardized waveform designations. They should not be rewritten as a casual statement that the pulse simply “rises for the first number and ends at the second.” Formal standards define front time, time to half value, virtual origin, and tolerances. Use the waveform label in a part-selection table and return to the applicable standard or generator manual when waveform calibration is the task.

Normalize the data sheet before comparing devices

A distributor table often preserves the largest-looking numbers while dropping their footnotes. A useful engineering table does the opposite: it keeps the test condition next to every value.

Manufacturers do not always use the same symbol for peak pulse power. Preserve the definition from each data sheet rather than standardizing the label and guessing what it means. The same rule applies to VC: record the current at which VC is specified in the adjacent column.

Equal VRWM does not make the remaining ratings equivalent

VRWM is a first filter for the normal operating-voltage window. It does not establish one unique breakdown range, clamp voltage, peak current, power rating, or thermal response. TVS products with the same VRWM can use different die sizes, packages, breakdown distributions, and test definitions.

A controlled review proceeds in this order:

1. Define the maximum continuous line voltage, polarity, temperature, and sustained abnormal states.

2. Identify the system surge standard, port, coupling mode, source impedance, polarity, count, and interval.

3. Estimate or measure the current that the protection branch can receive.

4. Read VC at the relevant current and waveform, then compare it with the protected circuit's allowed stress.

5. Review pulse power, thermal derating, and initial temperature instead of relying on one peak value.

6. Measure the TVS node and the protected node on the target board, then perform the equipment-level test.

If source impedance, coupling path, or protected-device limit is unknown, the output is a provisional shortlist. A released part selection requires those project conditions.

Compare VC at the same current point

Clamping voltage is not a current-independent constant. A data sheet normally reports VC at a specified IPP and waveform. The statement “device A has a lower VC than device B” is incomplete until both operating points are visible.

Start with the protected IC boundary and the PCB measurement point. That determines which current point and voltage matter. Searching for the lowest catalog VC without this boundary can hide leakage, package heating, and return-path overshoot.

A TVS data-sheet waveform is not the complete equipment test

IEC 61000-4-5 defines surge immunity test levels, equipment, setups, and procedures for electrical and electronic equipment. A TVS 8/20 μs rating describes the component under a specified pulse condition. The two are related, but the equipment test voltage is not a direct one-step conversion into a required TVS IPP.

The current at an equipment port depends on the generator, coupling/decoupling network, source impedance, port type, line-to-line or line-to-ground coupling, and the state of the equipment under test. The waveform at the TVS is then changed by PCB inductance, series impedance, and the device's dynamic behavior.

Keep the evidence layers separate:

• the product standard and IEC setup define the equipment-level test objective;

• the TVS data sheet supports component screening;

• oscilloscope measurements characterize the implemented board;

• the complete immunity test evaluates the equipment against its stated performance criterion.

A component data-sheet rating cannot guarantee the outcome of an arbitrary PCB layout.

Do not convert 10/1000 μs to 8/20 μs with a fixed ratio

Permissible peak current under a pulse depends on die thermal capacity, transient thermal impedance, initial junction temperature, package, and failure mechanism. The two waveform names do not contain enough information to create a universal current or power conversion.

Use a pulse-derating curve or multiple-waveform data only when the manufacturer provides it for the exact device and revision. If the data sheet covers one waveform only, request supporting data or arrange a controlled pulse test. A formula copied from another TVS family does not establish a rating for the device under review.

An analytical energy calculation can still be useful, but label it as a calculation and disclose the assumed waveform. It is not a measured device capability and should not be copied into the specification column.

When ASIM product data can be published

The ASIM product workbook includes fields such as VRWM, IPP, VC, and PPPM and can be used to locate candidate parts. Those cells do not consistently preserve the waveform, temperature, repetition condition, and formal data-sheet revision for every value. They are therefore not used as public rating evidence in this article.

Before a specific ASIM part enters a comparison table, the record needs:

• the current formal data sheet and complete orderable part number;

• the waveform and conditions for IPP, VC, and peak pulse power;

• thermal derating or a pulse-power curve;

• the project's continuous voltage, surge port, and coupling mode;

• the protected-device limit and target-board measurement point.

When all fields are available, the result can be presented as a normalized comparison. When they are not, the accurate output is a verification checklist.

Questions that often cause selection errors

Does a lower 10/1000 μs IPP mean a weaker TVS?

No. The number may be lower because the pulse is longer, and the device, package, temperature, or rating definition may also differ. Normalize the waveform and operating point before making a capability statement.

Does a larger PPPM guarantee a lower clamping voltage?

No. Peak pulse power and clamp voltage describe different aspects of behavior and both depend on test conditions. Compare VC at the same waveform and current point within an appropriate VRWM range.

What if the project waveform is not listed in the data sheet?

Do not apply a universal scaling factor. Obtain manufacturer pulse-derating data or controlled test evidence, then verify against the project's source impedance, duration, repetition count, and temperature.

Data and primary sources

• ROHM, Selection Method and Usage of TVS Diodes, No. 66AN047C Rev.001, December 2023 — waveform conditions for IPP and peak pulse power.

• IEC 61000-4-5:2014+AMD1:2017 CSV — scope, test equipment, setups, and procedures for surge immunity testing.

• AMETEK CTS: Surge Waveform Verification for Transient Generators — calibration context for combination-wave open-circuit voltage and short-circuit current.