UM1693 datasheet(35/196 Pages) STMICROELECTRONICS

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UM1693

Protection against battery transients

195

These hazards are generated by high current switching like relay contact, high current MOS

or IGBT switches, ignition systems, etc. The electromagnetic field generated by these

circuits directly affects lines or modules near the source of the electromagnetic radiation.

The schematic diagram in Figure 17 indicates how electromagnetic radiation creates such

hazards as electromagnetic interference in electronic modules.

Figure 17. Radiated hazards

3.3

Propagation of electrical hazards on the supply rail

Transients that are generated on the supply rail range mainly concern ISO7637-2 and

ISO10605 standards.

The most energetic transients are those resulting from load-dump and jump start. But all

other hazards may affect the normal operation of electronic modules.

The load-dump is caused by the discharged battery being disconnected from the alternator

while the alternator is generating charging current. This transient can last 400 ms and the

equivalent generator internal resistance is specified as 0.5

Ω minimum to 4 Ω maximum.

According to the ISO 7637-2 standard, the “+100 spikes” are due to supply sudden

interruption of currents in a device connected in parallel with the DUT due to the inductance

of the wiring harness, while the “-150 V spikes” are due to a supply disconnection from

inductive loads.

This chapter deals with voltage transient pulses, detailed on the ISO 7637-2 standard.

UM1693 Datasheet(PDF) 35 Page - STMicroelectronics