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TMS320F28335 ADC not corrected!

Dam Hung
Prodigy 140 points


Dear,

I am having a problem with ADC conversion in DSP. Even my input signal is good but the converted results is not correct.

My hardware configuration is: 1DSP controls the DC/DC converter, another one controls remaining DC/DC converter.

When DSP1 running, the noise make  DSP2 reads the ADC incorrectly. 

It has some noise as shown in picture: The read and yellow is DAC signal of ADC value. The noise repeats every ~4s and have oscillation of 40Hz. 

Please help!!! 

I think it come from the ADC reference voltage is noised.

  • 0
    Guru 192875 points

    Hi,

    Dam Hung said:
    It has some noise as shown in picture: The read and yellow is DAC signal of ADC value. The noise repeats every ~4s and have oscillation of 40Hz. 

    Is this when only controlCard in on and no power is being delivered or is it when the whole system is functional? Also, the claim that DSP1 is corrupting DSP2's ADC... nah doesn't make any sense!  BTW is DSP1 ADC readings very stable and only DSP2 struggles?

    Dam Hung said:
    I think it come from the ADC reference voltage is noised.

    Are you using the internal ref or external ref ? This again should not introduce noise like the one displayed above.

    Regards,

    Gautam

  • 0 in reply to Gautam Iyer
    Prodigy 140 points

    Dear,

    Thanks for your reply.

    In case DC/DC converters work, only DSP2 ADC has noise. I am using internal ADC reference.

    Update:
     - After I remove some capacitor filter of DSP2 (I am using customize DSP board), the noise is much reduced.
     - Add some capacitor at input of DC/DC converter, it also reduce the noise of DSP2 ADC.

    Thanks!

  • 0 in reply to Dam Hung
    TI__Guru 60865 points

    Hi Dam,

    If noise is coupling into one of the two devices, board design and layout seems like the most likely cause.  Have the board changes you made resolved the issue completely?  Let us know if you need help with further debug.