• State Resolved
  • Locked Locked
  • Replies 2 replies
  • Subscribers 82 subscribers
  • Views 698 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

TMS320F28379D: ADC showing slight variation

Akshay Godase
Intellectual 555 points

Part Number: TMS320F28379D
Other Parts Discussed in Thread: C2000WARE

Hi E2E team,

I am using adc_soc_epwm example from C2000ware for launchpad. I am reading values which are slightly deviated from my expectation. the ground of sensing circuit is common with launchpad's ground still I am seeing this deviation. I have attached images of both data read by Launchpad and what my multimeter shows. Please help me to figure out an issue.

for 2.308 I was expecting ADC read value as : 2865 but I am getting values approx equal to 2.5354248046875. 

How much tolerance I should expect?

Let me know if I am missing something.

THanks

  • 0
    TI__Guru 60865 points
    Hi Akshay,

    Refer to the schematic for the F28379D launchpad in C2000ware in \ti\c2000\C2000Ware_1_00_05_00\boards\LaunchPads\LAUNCHXL_F28379D\R2.0

    The VREFHI of the device is provided by REF5030, which is 3.0V.

    (2.3088/3.0)*4096 = 3152

    So it seems like the conversion results are roughly as expected (albeit very noisy based on your screen capture).

    Note that the device datasheet specifies the expected accuracy via the gain error, offset error, and INL/DNL specifications.

    If you have a low noise DC input, I'd expect a code spread of 2-4 LSBs over a small number of conversions (e.g. 64 conversions).
  • 0 in reply to Devin Cottier
    Intellectual 555 points
    Thanks for quick support as always.....!