AN901 Datasheet, PDF (12/14 Pages) STMicroelectronics – Electromagnetic compatibility

EMC GUIDELINES FOR MICROCONTROLLER-BASED APPLICATIONS
Test Description
The test is performed in compliance with standard IEC 1000-4-4.
Measurements are performed on a ground plane.
The generator is connected to ground plane by a short wire.
The HT wire is 10 cm from the ground plane.
The DUT is on the insulator 10 cm from the ground plane.
The first method consists of increasing the generator voltage until the MCU fails. If this method
demonstrates reproducibility problems (the voltage is lower than when the spike occurs), a
statistical method must be used.
3.4.2.3 Radio Frequency Interference
The radio frequency is a sine wave modulated with a 1-kHz signal. The frequency range is be-
tween 150-kHz and 1-GHz. In general, radio frequency interference (RFI) results from electro-
magnetic radiation. Both radiated and conducted EME tests (described in SAE and VDE spec-
ifications, respectively) are used by STMicroelectronics. The first gives a global description of
the MCU whereas the second gives a description of each pin.
The radiated EME tests are performed in a screened room. The DUT is completely isolated by
using special board according to standard SAE 1752.
The test is performed in compliance with standard IEC 1000-4-3.
The conducted EME test uses a coupling network similar to the one used for fast transients.
For each frequency, the voltage is increased until the MCU fails in order to characterize the
voltage/frequency interval of safe operation.
3.4.3 Interpretation of Results
The purpose of the described EMC measurements is to guide the Application Engineer during
EMC debugging phases and for the pre-qualification EMC test. Since these measurements
are not certified tests, which are the responsibility of specialized laboratories, there is no ab-
solute acceptance levels (which depend on the area of application). This process is designed
to detect EME peaks and sensitive frequencies that exceed accepted levels and in fixing these
defects.
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