AN901 Datasheet, PDF (10/14 Pages) STMicroelectronics – Electromagnetic compatibility

EMC GUIDELINES FOR MICROCONTROLLER-BASED APPLICATIONS
Figure 3. Voltage Divider Diagram
2 Noise Sources ^{120 Ω 47 nF}
51
50 Ω
~
MCU Schema
Voltage Divider
Spectrum Analyser
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
Energy
Rise time
- ESD
- Fast transient
- Radio Frequency
- Surge
- Discontinuity of
the power supply
1 ns
5 ns
30-1000 MHz
1.2 µs
in ms
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.
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