Load dump is a high-energy automotive transient that can occur when a battery is disconnected while the alternator is supplying current. The alternator and regulator response can create a voltage rise much longer than ESD or a microsecond-scale switching spike.
Load Dump Is Not One Universal Pulse
The test voltage, source resistance, duration and suppression condition depend on the vehicle architecture and applicable standard or OEM specification. A 12 V system, 24 V system and centrally suppressed alternator can produce different requirements.
Choose the Protection Technology by Location
High-power TVS diodes are widely used at module power inputs because they provide a controlled breakdown characteristic. MOVs can offer useful energy capability and bidirectional behavior in appropriate voltage ranges. MLVs are compact and valuable for lower-energy transients and ESD near sensitive signal or low-voltage power nodes. These names do not make the devices interchangeable.
Define the Voltage Window
The suppressor must remain off during jump start, charging tolerance and other permitted continuous conditions, yet clamp below the module’s damage threshold during the specified transient. Check the maximum value over temperature and tolerance, not only the nominal breakdown or V1mA.
Account for Source Resistance and Pulse Duration
Peak current depends on the difference between the source voltage and clamp voltage divided by the defined source resistance. Power and energy then depend on the time-domain waveform. An 8/20 microsecond surge-current rating alone cannot represent a load-dump pulse lasting tens or hundreds of milliseconds.
Coordinate the Complete Input
The protection device works with the connector, harness, reverse-polarity element, fuse, EMI filter, input capacitor and regulator. Trace inductance creates overshoot, while the input capacitor changes current sharing. Bench testing should use representative wiring and operating states.
Design Checklist
- Applicable ISO, regional or OEM pulse definition.
- 12 V or 24 V architecture and central suppression.
- Maximum continuous, jump-start and reverse-polarity conditions.
- Source voltage, resistance, duration and pulse count.
- Suppressor maximum clamp voltage over temperature.
- Peak power, pulse energy and cooling interval.
- Protected IC and capacitor absolute maximum ratings.
- AEC-Q qualification and change-control requirements where applicable.
Related Guides
Reference
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