• State Resolved
  • Locked Locked
  • Replies 7 replies
  • Subscribers 53 subscribers
  • Views 303 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

CC2340R2: Internal load cap default values

Luke
Expert 3750 points
Part Number: CC2340R2
Other Parts Discussed in Thread: SYSCONFIG

Tool/software:

Hi team,

I have been working with my customer to use SmartRF Studio to dial in their crystal accuracy but they need a more basic understanding of the internal cap array for documentation purposes.

The app note SWRA640H for CC13xx/CC26xx has information in section 6.4 in regards to the default value for the internal cap-array but there is no similar document for CC2340. 

Does the CC2340 have a default internal load cap value? Also, are the "trims" that you can override within SysConfig offsets from this default value? We have already found the chart on other E2E posts which gives approximate values from pre-release silicon to understand these trim values as well but want to ensure they are being used correctly. 

Thanks,
Luke

  • 0
    TI__Guru**** 217237 points

    Hi Luke,

    I will have to defer to the HW Team for default internal load cap values.  I believe the SysConfig HFXT Cap Array Trims overrides (adds CKMDSetInitialCapTrim / CKMDSetTargetCapTrim to ti_drivers_config.c Board_init) should be the same as the Smart RF Studio 8 Q1/Q2 values, but once more will get other experts to weigh in on this.

    Regards,
    Ryan

  • 0 in reply to Ryan Brown1
    TI__Expert 3750 points

    Hi Ryan,

    Thanks for the response! That aligns with our understanding as well. Please let me know whenever you find out the internal load cap values from the HW team and any other details.

    Thanks,

    Luke

  • 0 in reply to Luke
    TI__Expert 3750 points

    Team,

    Here is a bit more information on what they are seeing as well regarding the accuracy of the 48MHz crystal and resulting RF frequency. All the below observations are with no physical load caps on the PCBA.

    Manufacturing data

    In their last prototype build, they ran about 160 PCBAs through their BLE test stand. It measures the RF frequency at several BLE channels. Most of the RF frequency data measured better than +/- 5 ppm accuracy. These were good results. 

    Bench test data

    Using special test code, the actual 48MHz crystal frequency was measured on a few PCBAs. Again the results were better than +/- 5 ppm accuracy. Good results and matches the BLE test stand data.

    SmartRF Studio data

    With HFXT cap-array tuning set to Disabled or Use board settings, the resulting RF frequency was about + 6 ppm.

    ...set to Enabled and Q1=Q2=37, frequency was spot on.

    ...set to Enabled and Q1=Q2=35, frequency was about + 6 ppm.

    So, based on these results, I can't tell if they are currently Disabled, Using board settings (not sure what that means) or Enabled with Q1/Q2 = ~35.

    The data indicates they may want to be Enabled with Q1/Q2=37, but it'd be best to understand better before they pull the trigger on that.

    Again, any information on the default internal load cap array values would be super helpful as well! Slight smile 

    Thanks,

    Luke

  • 0 in reply to Luke
    TI__Guru**** 217237 points

    Would the customer be able to use host_test and DTM to verify that SysConfig settings are performing the same as Smart RF Studio 8?

    Regards,
    Ryan

  • 0 in reply to Ryan Brown1
    TI__Expert 3750 points

    Ryan,

    They have not used host_test given there is no R2 version and they wanted to avoid migrating it if possible and also don't have any DTM equipment right now either.  Are we not able to provide answers to the prior questions and/or share the internal load cap array values?

    Thanks,

    Luke 

  • 0 in reply to Luke
    TI__Expert 3750 points

    Hi team,

    Any update here?

    Thanks,

    Luke

  • +1 in reply to Luke
    TI__Expert 3630 points

    Hi Luke,

    When the HFXT cap array tuning is disabled, the default cap array values that was programmed at production will be used. I believe that at the moment it is 35.

    When the cap array tuning it is set to use board settings, it is suppose to use cap array values for our LaunchPad. However, this is not implemented for CC2340 yet. So if this option is selected, it will be the same as having the disabled option. It will just use the default FCFG settings.

    When the cap array is set to zero, the total effective capacitance will be around 3.7pF for our LaunchPad.

    If the customer wants to remove the frequency offset, they should have the cap array tuning enabled and change the cap array values to whatever gives the minimum frequency offset on their board.

    Regards,

    HG