AN2860

STM8 and EMC robustness

Doc ID 15267 Rev 5

5/17

1

STM8 and EMC robustness

Most STM8 product family applications require a high level of EMC robustness. The

considered level of robustness is closely linked to application purposes. The different levels

of robustness are defined by international EMC class standards together with criteria for

testing and measurement techniques used to classify these levels.

One of the pivotal IEC (international electrotechnical commission) standards is the IEC

61000 standard which defines the following robustness classes:

–

Class A: No failure detected

–

Class B: Failure detected but self-recovery after disturbance

–

Class C: An external user action needed to recover normal functionality

–

Class D: Normal functionality cannot be recovered

Note:

IEC is a world wide recognized authority on international standards for a vast range of safety

issues concerning electrical, electronic and related technologies. It is important to note that

there are several other recognized bodies concerning electronic safety standards besides

IEC, such as VDE in Germany, IET in the United Kingdom and the IEEE in the United

States.

Class B has a different meaning from that used in the IEC 61000 standard as it means in

this case that the application is classified from a safety point of view. See the IEC 60335

standard in the AN3181: Guidelines for obtaining IEC60335 Class B certification on STM8

family.

EMC robustness is a complex result of several factors and it depends on the component

design. However, a very good EMC robustness of any component may be degraded by its

incorrect position into the PCB design or by an incorrect hardware project. These factors are

discussed in more details in the next chapters.

Another important factor is the software solution which can significantly improve the

robustness of the application by a proper software reaction when any disturbance is

detected, which is fundamental, especially for Class-B compliant applications.

In most cases, it is possible to recover the application internally even if the user is not aware

of the internal issues. It is also possible to predict an imminent error state by using some

efficient techniques capable of testing permanently if both the MCU and the application work

properly.

Note:

These techniques are further described in the following documents: application notes

AN1015 (Software techniques for improving microcontroller EMC performance) and

AN3181 (Guidelines for obtaining IEC60335 Class B certification on STM8 family).