STM32F0 GPIO PAL Input Analog Issue

[samtatasurya]

Have you read AN2834 Application Note ?
http://www.st.com/web/en/resource/technical/document/application_note/CD00211314.pdf

Hi Jacon,

Unfortunately after reading the application note, there didn't seem to be issue that's exactly as what I'm facing.
At the first glance, I thought it is the "High Impedance Source Measurement", as they have repeated pattern of noise, but the "pulse" that I'm facing is not exactly having decaying pattern as in the application note.

Nonetheless, thank you for the suggestion to look into that! It'll definitely help me designing more robust sampling system once I tackle the above-mentioned issues!

- Sam

[steved]

What is the source resistance of your analog source? A sample and hold often causes an analog input to take a short spike of current while sampling, since the input can be connected almost directly to a small capacitor.

There's a table in the data sheet (Table 55 in DM00039193 - page 78 on Rev 3) linking analog source impedance time to minimum sampling time.

[samtatasurya]

What is the source resistance of your analog source? A sample and hold often causes an analog input to take a short spike of current while sampling, since the input can be connected almost directly to a small capacitor.

There's a table in the data sheet (Table 55 in DM00039193 - page 78 on Rev 3) linking analog source impedance time to minimum sampling time.

Hi steved,

Thank you for showing this information. My input impedance is around 5k, and my current sampling duration is 28.5 cycles.
Therefore, it is still within the limit of the one specified in the data sheet (max 25.2k for 28.5 sampling cycles).

- Sam