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CC2340R5-Q1: Crystal cap_array tuning

ching jen Chuang
Prodigy 25 points
Part Number: CC2340R5-Q1
Other Parts Discussed in Thread: SYSCONFIG, LP-XDS110ET

Tool/software:

Hi teams,

We are testing the frequency on the CC2340, and we know that we can tune the Q1 & Q2 values with SmartRF 8. 

We have some questions about the test interface.

In the RF test column "HFXT cap-array tuning",  what is the meaning of "disable" & "Use board settings"

1. Does "disable" mean CC2340 does not use the integrated capacitors and needs external load capacitors?

2. Does "Use board settings" mean CC2340 uses the setting with what we set in SysConfig?

If we set Q1 = Q2 = 0 in SysConfig, should the frequency using "Use board settings" be the same as "Enable" with Q1 = Q2 = 0?

Many thanks,

Jesse

  • 0
    TI__Intellectual 850 points

    Hi Jesse,

    Setting Q1 = Q2 = 0 would mean the capacitance would be around 3.5pF. The capacitor array trim code is from 0x0 to 0x64 which gives the value from 3.5pF to 10.5pF.

    Disabling this would mean that you are using external caps. Enabling this would mean that the internal cap array is being used.

    For, "board settings", I will get back to you on this after verification. Thank you!

    Best Regards,
    Cashmere


  • +1 in reply to Cashmere Ramos
    TI__Intellectual 850 points

    Hi,

    The "use board settings" is only for the pre-defined settings for each board (usually depends on the TI EVM) so we would not recommend using this option if you have a custom board. Furthermore, there is no predefined setting for CC2340 since we have two versions of EVMs (Q1 and non-Q). Please use either "Disabled" or "Enabled". Thank you!

    Best Regards,
    Cashmere

  • 0 in reply to Cashmere Ramos
    Prodigy 25 points

    Hi Cashmere,

    We are now testing the frequency on EVM to familiar with the test operation. This allows us to test the custom board as soon as it arrives.

    1. In our test, we found that when we choose "disable", "use board setting" and "enable with Q1=Q2=35", the frequency is totally the same. I would like to know how much capacitance the internal capacitor contributes to the Cload when “disable” is selected.

    2. Now we use the LP-XDS110ET through the USB to connect SmartRF 8 on PC. Can we also connect the SmartRF 8 through the USB-to-Uart port on custom board?

    3. We also try to use the btool HCIExt_ModemTestTxCmd,. We already set Q1=Q2=0 in Sysconfig. but the frequency is faster 40KHz than "SmartRF 8 enable with Q1=Q2=0" (both are channel 39 & 0 dbm Tx power), should they show the same frequency in the test or there is still another reason causing the difference between HCIExt_ModemTestTxCmd & SmartRF. If so, should we refer to btool or SmartRF 8 in our design?

    4. In SamrtRF 8, Does RF compensation is the default open? That may be Why we have different because we close it in our Sysconfig.

    Many thanks,

    Jesse

  • 0
    Prodigy 25 points

    Hi Cashmere,

    We also have another question. We'll send our custom board to the crystal vendor for Crystal Circuit Evaluation.

    Is the Crystal working when the power supply is on? Or any mode you recommend when testing the crystal itself?

  • 0
    TI__Intellectual 850 points

    Hi Jesse,

    I would just like to provide a clearer answer from the questions below. After careful checking, please refer to this instead:

    Enabled = internal cap array is working as configured
    Use board settings = the internal cap array was predefined in the settings and will therefore be used. for example, for CC27XX, it is around 0x33. For CC23XX, there is no predefined setting so we would not recommend to use this.
    Disabled = This refers to the configured Q1 and Q2 from FCFG.

    If you would like to keep the internal array to a minimum, please use 0 as the value but keep it enabled.

    for number 2, ill get back to you on that.

    3. May I know which temperature range are you measuring when this deviation is observed? This could be affected by the SW TCXO if you have enabled this when flashing host test.

    4. SmartRF Studio's RF test firmware hard-codes the current temperature to 25 degrees C. TX output power can be inaccurate when running RF tests at higher or lower temperatures.

    5. The 48MHz only turns on right before radio activity.