AN901 Datasheet, PDF (11/14 Pages) STMicroelectronics – Electromagnetic compatibility

EMC GUIDELINES FOR MICROCONTROLLER-BASED APPLICATIONS
For air-discharge tests, the product is placed on a ground plane separated with 10 cm of insu-
lation.
Discharges are made on the ground plane.
A statistical method gives more reproducible results.
3.4.2.2 Fast Transients
This test consists of coupling these disturbances to the power supply or to the I/O of the MCU.
Fast transients are generated by switches or relays.
Fast transients are described in standard IEC.1000-4-4.
Figure 5. Disturbance Diagram
3
100 ns
0.9
0.5
50ns
0.1
300 ns
5ns
The spike frequency is 5 kHz. The generator produces bursts of spikes that last 15 ms every
300 ms.
The fast transients are coupled to the device under test (DUT) with capacitors C_C. An attenu-
ator must be used because the burst generators are too powerful to be directly applied to the
components.
Figure 6. Coupling Network
To Power Supply
C_c
mm
mm ^Cc
To the DUT
Decoupling Network
Power Supply Network
The fast transients are coupled to the I/O with a small capacitor.
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