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CC1121: TCXO CC112x Issues

Zebryk
Expert 1240 points
Part Number: CC1121
Other Parts Discussed in Thread: CC1120

Hello,

Wondering if anyone has any issues with installing a TCXO into a CC1120 420-470MHz EVM?

Accidentally, our CM did not remove the XTAL in the process of conversion.

8 of 10 units have now failed.

Does this make sense?

CC112xEM_420_470_schematic.pdf

  • 0
    TI__Guru**** 317180 points
    No, as long as XOSC_Q1 is grounded it shouldn't matter if the xtal is mounted or not. Does the failed board work if you remove the xtal?

    Which swing to you see on the EXT_XOSC pin?
  • 0 in reply to TER
    Expert 1240 points

    TER,

    Before I do anything to influence your diagnostics, I currently have (2) operational units and (2) bad units.

    I think the (2) good units are ok for both TX and RX.

    Bad Unit X3 reports "No chip" but with a air-coupled RF probe indicates the TXCO is alive at 32MHz.

    Bad Unit X1 also shows the TXCO is alive at 32MHz.

    FYI...X1 has been working fine for some weeks.

    ----Mostly in a TX role.

    ---Switching it to RX role may have contributed somehow?

    As both X1 and X3 are dead regardless, I can remove the XO and report my findings?

    Are there any tests you would like me to perform on the working units?

    Thanks,

    Jay Zebryk

  • 0 in reply to Zebryk
    TI__Guru**** 317180 points
    Which TCXO are you using?

    On the dead units, please go ahead and remove the xtal . Is the voltage on all pins (RBIAS, *DECOUPL) as expected?

    If the TCXO is running it should normally be possible to get the SPI interface up and running and at least be able to read out the PARTVERSION (the device should be recognized by SmartRF Studio)
  • 0 in reply to TER
    Expert 1240 points

    TER,

    I apologize for the delay in replying.

    No improvement when removing the XO.

    Seems like either a soldering issue or that I am using the wrong TCXO.

    In at least one case, spraying the EVM with a can of air resulted in revival for a time, then failure 5-10 minutes later and so on.

    In one case, something on the EVM was pulling down the rail very low. (Virtually a short.)

    Below is a link to the TCXO that I selected from Digi-Key as it was readily available:

    www.taitien.com/.../XO-0081_TY.pdf

    If this was a poor choice, please suggest another better suited for lab purposes.

    Thanks,

    --

    Jay Zebryk

  • 0 in reply to Zebryk
    TI__Guru**** 317180 points
    The TCXO looks ok as far as I can see from the datasheet.

    Have you tried to measure the impedance on the non working board from every pin to ground and between every pin that could be in contact with each other (and compare with a know good board)? This way it should be possible to identify the part of the board that causes a near short.