assembler2

In FFT mode, the Analog Discovery 2 shows a peak of just under 20db on the first channel at 142kHz and 5Mhz or multiples thereof, respectively, compared to the noise level. With a second tested device, these peaks are visible on both channels. The adapter board is used and the BNC inputs are short-circuited. However, the effect is also visible without the adapter board. A different USB supply and a change of location (to exclude electromagnetic interference) did not show any changes. It seems to be a problem of the ADC or the input stage. According to the reference manual, the 3.3V and 1.8V logic supplies each clock at 3MHz and the 3.3V logic supply clocks at 2.5MHz. Are the visible peaks multiples of the 3.3V logic supply? Where does the 142kHz come from? Workspace_1kHz_80kHz.dwf3work Workspace_1MHz_3MHz.dwf3work Workspace_3MHz_50MHz.dwf3work