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EMC GUIDELINES FOR MICROCONTROLLER-BASED APPLICATIONS

Figure 3. Voltage Divider Diagram

3.4.2 EME Immunity Tests

There are an infinite number of disturbances, but the principal types can be classified ac-

cording to their spectrum.

Figure 4. Disturbance Spectrum Diagram

The discontinuity of the power supply is irrelevant since electrical energy is not stored in

MCUs.

The Surge test does not affect the microcontroller as long as the supply voltage remains cor-

rect since the rise time is much greater when compared to the clock period.

STMicroelectronics focuses it efforts on ESDs and fast transients.

3.4.2.1 Electrostatic Discharges

Electrostatic discharge (ESD) tests, in compliance with standard IEC 1000-4-2, are very im-

portant to ensure that the application is not disturbed by the high amount of static voltage pro-

duced by the human body.

There are two types of tests; air-discharge tests that use a spherical tip and contact discharge

tests that use a conical tip.

For contact discharge tests, the tips are placed on the pins and the ESD voltage is in the

0-8 kV range.

~

50

Ω

120

Ω 47 nF

2 Noise Sources

51

Voltage Divider

Spectrum Analyser

MCU Schema

Rise time

Energy

- ESD

- Fast transient

- Radio Frequency

- Surge

- Discontinuity of

the power supply

1 ns

5 ns

1.2 µs

in ms

30-1000 MHz