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Hello TI,
Here a brief description of the EMC problem:
The device, an industrial PC complied with all necessary EMC tests in the laboratory, except the DIN EN 61000-4-6 test.
This test applies RF stress over the frequency range 150kHz–80MHz (10V and 80% AM Modulation with 1KHz ) to the power cables.
During the EMC impact, the Touch (ADS7846 controller) reacts no longer but continuous working if the electromagnetic interference is over.
The test setup is that the DUT is in 10cm distance to the GND reference plan (capacitive coupling).
If the metallic housing of the industrial PC and the reference plane are shortened, the touch is immune to the interference.
Hence, it seems that the capacitively-coupled voltage stress and not the magnetically coupled current influence is the main cause of the problem.
The question is how it's possible to improve the touch immunity against this EMC interference.
I also like to mention that the ADS7846 X and Y inputs are filtered by the means of a PI Low Pass Filter.
I would appreciate ideas to cure this EMC problem.
Kind regards
Gottfried Kloyer
