The pulse tests a power line faces are not one test but a landscape: component-level ESD, system-level ESD, mains surge, and automotive transients each have a generator, a waveform, and an energy. This guide maps the landscape, explains each test, and shows how the protection component is chosen for the test that matters.
The Pulse Test Landscape
The tests divide by level and by phenomenon. Component-level ESD classification—human body model and charged device model—tells how the part survives handling. System-level tests—IEC 61000-4-2 for electrostatic discharge, IEC 61000-4-5 for surge, and ISO 7637 for automotive conducted transients—tell how the assembled product survives the field. The protection component must cover the system-level event while surviving the component-level class it is rated for.
The landscape also explains why a single number never closes the discussion: an 8 kV ESD event carries little energy but arrives in nanoseconds, while a surge event at 1 kV carries orders of magnitude more energy over tens of microseconds. The TVS that clamps the first may not absorb the second, and the selection reads the waveform, not the voltage alone.
ESD: HBM and IEC 61000-4-2 Basics
The human body model represents a charged person touching the part, modeled as a capacitor discharging through a resistor—the classic 100 pF and 1.5 kΩ network—and it classifies the component’s own robustness. The system-level counterpart, IEC 61000-4-2, applies contact and air discharges to the product enclosure and ports, with test levels rising from 2 kV to 8 kV for contact discharge and higher for air discharge, depending on the installation class.
The ESD waveform is fast: a few nanoseconds to the peak and a decay over tens of nanoseconds, which makes the protection’s response time and its placement the deciding factors. A TVS or ESD diode at the connector clamps the fast edge before it travels, and the layout loop between the clamp and the protected circuit is part of the protection, as the TVS placement guide explains.
ESD Beyond the Discharge Path.
The ESD event also reaches the circuit through the enclosure and the cabling: a discharge to the housing couples into the board, and a discharge near a connector enters through the harness. The protection reads the possible paths—the port, the shield, the chassis connection—and the clamp is placed where each path meets the board. Soft failures matter as much as damage: a reset or a corrupted read after an ESD event is a compliance failure even when every part survives, and the layout and the filtering are part of the fix. The ESD test’s pass criterion is the product’s behavior, not only the parts’ survival.
Surge: IEC 61000-4-5 Waveforms and Coupling
IEC 61000-4-5 defines the surge test for unidirectional surges from switching and lightning transients. The generator produces a 1.2/50 µs open-circuit voltage wave and an 8/20 µs short-circuit current wave, coupled into the line according to the port and the installation class; a separate 10/700 µs generator is specified for external telecommunication lines. Test levels rise with the installation environment, from a few hundred volts in protected indoor settings to kilovolts at the service entry.
The surge carries real energy: at the 8/20 µs shape, the TVS absorbs a pulse that the datasheet’s pulse-power rating must cover at that width and at the working temperature. The surge-current ratings article owns the rating method; the testing article’s point is that the waveform and the coupling determine which rating column the part is read against.
Coupling Modes and the Generator.
The surge is injected in defined coupling modes—line-to-line and line-to-earth—through coupling networks that shape the wave, and the generator presents a defined source impedance that differs between the mains coupling and the telecom coupling. The mode decides the voltage the protection sees: a line-to-earth event stresses the insulation and the return path, while a line-to-line event stresses the clamp directly. The test setup is part of the record—the coupling, the level, and the ambient are stated with the result—so the mapping from test to rating column is reproducible.
Automotive Transients: ISO 7637 Context
The automotive power line adds its own transient family, defined by ISO 7637-2 for 12 V and 24 V systems: the inductive-load pulses, the switching spikes, the supply-voltage dropouts, and the load-dump pulse from the alternator. The load-dump pulse is the high-energy member of the family, and it is the one that drives the protection choice toward a higher pulse-power class or a series protection stage.
The automotive tests are applied with the vehicle’s operating modes in mind, and the result is judged against the performance classes the standard defines. The protection design reads the family, not a single pulse: the TVS or clamping stage is sized for the load dump, while the faster spikes are handled by the same clamp’s response and the layout.
The Automotive Family in the Real Vehicle.
The family also includes the supply-dip and the cranking events, where the rail falls rather than rises, and the protection must let the load ride through without a false reset. The review reads the falling events separately from the rising ones, because the series element and the clamp behave differently in each direction. The performance classes in the standard name what the equipment may do during each event—no degradation, temporary degradation with recovery, or a defined function loss—and the product’s target class is set before the test, not after.
Mapping Tests to Protection Components
| Test | Waveform | Protection component | Rating to check |
|---|---|---|---|
| Component ESD (HBM) | 100 pF / 1.5 kΩ pulse | Device’s own class | ESD classification |
| System ESD (IEC 61000-4-2) | Fast discharge, ns edge | TVS/ESD diode at port | Clamp, capacitance, response |
| Surge (IEC 61000-4-5) | 1.2/50 µs, 8/20 µs | TVS | Pulse power at the width |
| Automotive load dump (ISO 7637) | Long, high-energy pulse | Higher-class TVS or series stage | Pulse power, derating |
The mapping is the article’s core: each test names a component and a rating column. The ASMBJ28CA—the 28 V, 600 W TVS in SMB (DO-214AA) positioned for automotive lines on the Good-Ark site—is the class example for the automotive power and lighting lines, with the full clamping parameters confirmed with the supplier before the rating column is locked.
The Rating Table for the Event.
The mapping closes with the rating table: the pulse-power at the event’s width and temperature, the clamping voltage at the rated pulse current, the leakage at the working temperature, and the response the layout provides. The table is read against the protected component’s limits, and the margin is the difference between the clamp’s peak and the limit. The confirmation with the supplier covers the values the site does not publish, and the first board verification repeats the test with the product’s actual generator settings.
The First Board Verification.
The first board run repeats the mapping with the product’s generator settings: the clamp waveform at the protected node, the peak, and the margin are measured and compared with the rating table. The verification is the mapping’s proof, and the record ties the test setup to the result.
Measurement note. Generator calibration, coupling/decoupling networks, and the equipment configuration follow the current editions of the standards; results are recorded with the waveform, the level, and the ambient so that the protection mapping is reproducible.
Frequently Asked Questions
What is the difference between ESD and surge?
ESD is fast and low-energy, while surge is slower and carries far more energy; the two tests are read against different rating columns.
What is the HBM?
A component-level model of a charged person discharging through 100 pF and 1.5 kΩ, used to classify the part’s handling robustness.
Which waveforms does IEC 61000-4-5 use?
The 1.2/50 µs open-circuit voltage and 8/20 µs short-circuit current for the combined wave, plus a 10/700 µs generator for external telecom lines.
What is the load-dump pulse?
The high-energy automotive transient from the alternator, the member of the ISO 7637 family that drives the protection toward a higher pulse-power class.
How do I map a test to a part?
Name the waveform, read the pulse-power and clamping rating at that width and temperature, and place the clamp so its response reaches the protected node in time.
Conclusion
The pulse landscape is a mapping exercise: HBM and IEC 61000-4-2 for the fast ESD edge, IEC 61000-4-5 for the surge energy, and ISO 7637 for the automotive family, each tied to a component and a rating column. Read the waveform, confirm the rating, and the protection follows.
Review the New Release automotive parts on the Good-Ark site, and send Good-Ark your test standard, level, and protected-component limits for a protection recommendation.