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ADC3241: Odd bit error in ADC3241

user4199584
Prodigy 100 points
Other Parts Discussed in Thread: ADC3241

art Number: ADC3241

Hi, TI experts

 

I use ADC3241 in a design and find a very strange issue. The ADC is sampling at 25Msps. The 7-th bit in the serial LVDS are 0 and 1 alternately, independent with the input voltage or other bits.

The following figures is the results of 0-V input, the 101010... sequence is obvious from the display of the oscilloscope.

What's wrong with this ADC? Is there any solution?

Thanks for your help.

 

Qian

 

  • 0
    TI__Mastermind 18065 points

    Qian:

    Yes, very strange.  Have you verified the programming and set-up on the TI EVM with TI capture card tool?  If possible, this is recommended to ensure that there is not a software or set-up issue.

    Is this is 1-wire or 2-wire mode?  Can you check and verify the timing diagram in section 9.3.3.2 of the datasheet.  In the plot above you may be showing the 2-wire serial output that are alternating 0 and 1.  Check the frame clock alignment.  Given the 7th bit issue there may be some mis-alignment there.

    --RJH

  • 0 in reply to RJ Hopper
    Prodigy 100 points

    RJH

    This problem occurs with both 1-wire and 2-wire mode. To illustrate it more clearly, AD3241 is set up to 1-wire, in the oscilloscope picture.

    I do not have an EVM board in hand, so I can not verify this issue with the EVM and capture card. But I will follow your instruction to find the mis-alignment.

    I will post here, if I make some progress.

    Qian

  • 0 in reply to RJ Hopper
    Prodigy 100 points

    RJH

    We have checked the timings of serial data, FCLK and DCLK, all are right.

    What is the next step we can try? Thanks.

    Qian

  • 0 in reply to user4199584
    TI__Expert 4880 points

    Qian,

    I would suggest enabling a few different ADC test patterns functionality. For each test, check and see if the problem you see with bit7 remains. Perform these tests in both 1-wire and 2-wire mode. 

    Reference section 9.6.2.8 on page 61 of the datasheet. You should find Table 17 (also pasted below) which shows how to program register 0Ah for a variety of pattern tests. Let me know your results. 

    Thanks 

    Yusuf