AN2689 datasheet(4/42 Pages) STMICROELECTRONICS

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Electrical hazards in the automotive environment

AN2689

4/42

Doc ID 14310 Rev 3

Electrical hazards in the automotive environment

The automotive environment is the source of many electrical hazards. These hazards, such

as electromagnetic interference, electrostatic discharges and other electrical disturbances

are generated by various accessories like ignition, relay contacts, alternator, injectors,

SMPS (i.e. HID front lights) and other accessories.

These hazards can occur directly in the wiring harness in case of conducted hazards, or be

applied indirectly to the electronic modules by radiation. These generated hazards can

impact the electronics in two ways - either on the data lines or on the supply rail wires,

depending on the environment.

1.1

Source of hazards

1.1.1

Conducted hazards

These hazards occur directly in the cable harness. They are generated by inductive loads

like electro-valves, solenoids, alternators, etc.

The schematic in Figure 1 shows a typical configuration.

Figure 1.

Conducted hazards

1.1.2

Radiated hazards

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 2 indicates how electromagnetic radiation creates such

hazards as electromagnetic interference in electronic modules.

Source of

distrubances

Equipment

needing protection

ECU

Alternator

Battery

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