• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 82 subscribers
  • Views 173 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TMS320F28P650DK: The problem of 16-bit ADC sampling

Steven Xu
Prodigy 110 points
Part Number: TMS320F28P650DK
Other Parts Discussed in Thread: LAUNCHXL-F28P65X

Tool/software:

Hi, expert

I am encountering a problem now when using the 16-bit high-precision ADC sampling of the TMS320F28P65 chip. Have you ever faced such a situation?

The problem description is: When I used the demo board（LAUNCHXL-F28P65X） to sample the voltage at both ends of the dry battery, I found that when the sampling configuration of the ADC was set to 16-bit precision single-ended sampling, through the online simulation of CCS, it could be seen that the fluctuation of the sampling value was very large, approximately 200 LSB. However, when I set it to 16-bit precision differential sampling, the fluctuation of the sampling value in the online simulation was very small, only about 20 LSB. Other configurations were the same, and an external ADC reference was used, with a sampling window of 64 and a 1/4 clock divider. So, do you have any ideas about this situation?

  • 0
    TI__Genius 10941 points

    Hello Steven,

    Do you have any kind of signal conditioning applied to the ADC input? For operation in 16-bit mode, without signal conditioning e.g. a small cap on the input pin, it is likely for variations to occur.

    Can you provide an oscilloscope capture of the voltage at the ADC input? 200 LSB corresponds to about 9mV of variation with a 3.0V reference. 

    I would also try longer sampling windows to see if the variation reduces. But you should definitely put a cap on that pin if you want to see stable conversions in 16-bit mode.

    Best regards,
    Ibukun