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Electrical characteristics
ST72324B-Auto
12.8
EMC characteristics
Susceptibility tests are performed on a sample basis during product characterization.
12.8.1
Functional electromagnetic susceptibility (EMS)
Based on a simple running application on the product (toggling two LEDs through I/O ports),
the product is stressed by two electromagnetic events until a failure occurs (indicated by the
LEDs).
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ESD: Electrostatic discharge (positive and negative) is applied on all pins of the device
until a functional disturbance occurs. This test conforms with the IEC 1000-4-2
standard.
●
FTB: A burst of fast transient voltage (positive and negative) is applied to VDD and VSS
through a 100pF capacitor, until a functional disturbance occurs. This test conforms
with the IEC 1000-4-4 standard.
A device reset allows normal operations to be resumed. The test results given in
Table 101on page 161 are based on the EMS levels and classes defined in application note AN1709.
Designing hardened software to avoid noise problems
EMC characterization and optimization are performed at component level with a typical
application environment and simplified MCU software. It should be noted that good EMC
performance is highly dependent on the user application and the software in particular.
Therefore it is recommended that the user applies EMC software optimization and
prequalification tests in relation with the EMC level requested for his application.
Software recommendations
The software flowchart must include the management of runaway conditions such as:
●
corrupted program counter
●
unexpected reset
●
critical data corruption (control registers...)
Prequalification trials
Most of the common failures (unexpected reset and program counter corruption) can be
reproduced by manually forcing a low state on the reset pin or the oscillator pins for 1
second.
To complete these trials, ESD stress can be applied directly on the device, over the range of
specification values. When unexpected behavior is detected, the software can be hardened
to prevent unrecoverable errors occurring (see application note AN1015).