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DDC114 Capacity Range Problems

ROMAN MAHERA
Prodigy 40 points
Other Parts Discussed in Thread: DDC114

We use DDC114 adc in one of our device. Only Input_1 is in use, other inputs are floating.

It behaviors as follow: 

- Works as expected if initially range with maximum capacity is chosen [all range pins are high] .

Digital output looks like it should be [ex. 0000 0000 0000 000F FFFF ]. 

- Works unpredictably when capacity range is changed to any value [if any of range pins is low or any are].

Digital output is incorrect. For example   075F 1043 B407 4FB0 3A44. Reminder: Only Input_1 is attached, other inputs are floating.

Any tries go back to maximum range does not solve the output [adc show values on all inputs]

- 180mV voltage still presents on REF pin after removing reference voltage. [That is very strange] 

Does anybody had the situation like this ? Are there any explanations?

  • 0
    TI__Mastermind 18285 points
    Roman,

    We have received your post and hope to have a response back to you soon.
  • 0
    TI__Guru 65450 points
    Roman,

    Thanks for posting, sorry about the delay. I am applications support for the DDC products. Could you help clarify a few things please?

    Are you saturating the chip when you see FFFFF for the one input? What magnitude of current are you integrating? The channels you are not using should not show 0 but instead show some pre-programmed offset value. are you in 20-bit mode? Which ground are you using to tie the range pins low? Are you checking Dvalid to make sure it is toggling and therefore that data output is valid? Can you provide me a diagram of your DCLK, DVALID, CONV, DOUT? I need to see the timing relationships. Have you tried using the test mode to disconnect the inputs and check the output of all 4 channels? Do you see this issue on one device or many?

    According to your output you are getting in error I see, ~30k codes for two channels and around half that for the other two, please confirm.

    These answers should help to figure out what debug we can do.

    Regards,

    -Adam