AN2689 datasheet(40/42 Pages) STMICROELECTRONICS

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Conclusion

AN2689

40/42

Doc ID 14310 Rev 3

Figure 63 shows a recommended PCB layout using a protection device close to the

accessories connector, and with the track loop to the module to protect minimized.

Figure 63.

Placement and routing of a protection device

Conclusion

Because the automotive environment is a major source of electrical hazards and electronic

equipment is becoming more sensitive, caution must be taken when electronic modules are

designed.

It is therefore very common to use protection devices to ensure the modules and systems

are safe from all hazards generated inside the vehicle.

The choice of the protection device is not easy, and moreover, surges are not well defined

even by the standards. This document helps the electronic module designer in the selection

of the protection device.

Calculations are sometimes good enough to dimension the protection device but in some

cases the surges in practice have to be monitored to determine the best protection.

Some worked examples are given in this document, particularly for the IEC 10605 and ISO

7637-2, pulse 2 and pulse 5a. Thus the way these cases are treated offers the designer a

starting point for other kinds of surge, which are yet to be defined.

Beyond the guidance offered for choosing protection devices on the basis of standard

surges, other advice is given at the same time such as the protection device routing on PCB,

the PCB layout optimization, and the protection device placement.

As a result this document should be helpful in all automotive protection design approaches.

Module to protect

Vnom

Vmax

Transil

AN2689 데이터시트(PDF) 40 Page - STMicroelectronics