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CC2543: Frequency drift due to temperature rise

Ca Suu
Prodigy 20 points
Part Number: CC2543

Tool/software:

Based on the standard circuit published by TI, I created a wireless circuit using the CC2543RHBR and XRCGB32M000F2P10R0 (Murata).

When I checked with a spectrum analyzer, I found that as the ambient temperature rises, the wireless frequency starts to shift.

This phenomenon occurs when the temperature rises by approximately 122°F from the start of operation. For example, starting at 68°F, the wireless frequency starts to shift around 158°F, and at around 176°F, the frequency drifts by more than 10 MHz.

Resetting the power to the wireless circuit restores the wireless frequency to normal.

This phenomenon also occurs when the temperature decreases. (For instance, after resetting the power at 167°F, the phenomenon occurs as the temperature drops to around 77°F.)

Does anyone know the cause of this issue or have any potential solutions?

  • 0
    TI__Expert 6020 points

    Hello,

    Based on the description of the problem I don't have an immediate answer. Can you provide some additional detail:

    • Is this for a system already in production? Is this unique to one device or does this occur on all devices tested?
    • This testing is being done with a crystal that doesn't meet the data sheet specification for CC2543. Can you repeat the testing to see if the correct crystal resolves the issue you are seeing?
      • The crystal has a max ESR of 70-ohm vs. the device requirement of 60-ohm
      • The crystal has a target load impedance of 6pF where the crystal load capacitance should be between 10pF and 16pF
    • Once the above is complete, if the issue still exists you can request a schematic and layout review.

    Thanks,

    Jake

  • 0 in reply to Jake Pulliam
    Prodigy 20 points

    Hello Jake,

    Thank you for your prompt response and for pointing out the potential issues with the crystal specifications.

    To answer your questions:

    This is not yet in production; we are still in the testing phase. The issue occurs on all devices tested so far. We will proceed with testing using a crystal that meets the data sheet specifications for the CC2543, specifically addressing the ESR and load capacitance values you mentioned.

    Thank you again for your assistance.

    Best regards, 

  • 0
    Prodigy 20 points

    The same phenomenon occurred even when using the evaluation board from TI.

    Therefore, I am investigating the settings. Could you explain the register PRF_CHAN.SYNTH_ON? Currently, it is always set to 1 during operation. The phenomenon does not occur if it is constantly set to 0 or if it is repeatedly switched from 1 to 0.

    Does anyone know the reason for this?

  • 0 in reply to Ca Suu
    TI__Expert 6020 points

    Hello,

    I found reference to this setting here:

    https://e2e.ti.com/support/wireless-connectivity/other-wireless-group/other-wireless/f/other-wireless-technologies-forum/195091/cc2543-2544-radio-frequency-synthesizer-calibration

    It looks like if the synth is always on then it would lead to issues with calibration over a wide temperature range.  For more information I would refer you to the TRM https://www.ti.com/lit/ug/swru283b/swru283b.pdf :