Thank you Ioannis for your effort ! .. you spend a time for me. The problem is solved, I don't understand what happened really.
So, on AN0 I had a TC1047 ( analog temperature sensor ) with a 100nF capacitor to ground. The voltage measured on AN0 was 726 mV , also I verified with a osciloscop and I had a "clean" voltage. After I removed the capacitor, AN0 work well .
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