AN2689 datasheet(38/42 Pages) STMICROELECTRONICS

Part #	AN2689

Description	Protection of automotive electronics from electrical hazards

PDF	42 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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38 / 42 page

PCB layout recommendations

AN2689

38/42

Doc ID 14310 Rev 3

Inductive coupling is also present on the PCB. This is sometime also called “inductive cross-

talk”. When over voltage occurs, a current crosses the track and makes this track radiate.

This coupling depends on the current variation rate (di/dt). The parasitic inductance coupling

is shown in Figure 58.

Figure 58.

Inductive coupling representation

Like capacitive coupling, the longer the tracks to the protection device the larger will be the

electromagnetic field.

The solution to minimize the capacitive and inductive coupling consists of placing the

protection device as close as possible to the accessories connector, where the surge impact

is the most probable. (Figure 59)

Figure 59.

Where to place the protection device

Vsurge

Isu

Module to protect

Vnom

Vmax

Transil

AN2689 Datasheet(PDF) 38 Page - STMicroelectronics