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Original question:

CC2340R5-Q1: Crystal cap_array tuning

CC2340R5-Q1: Crystal cap_array tuning

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

Tool/software:

Hi teams,

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 the 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's 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?

5. 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?

These are extensions of the previous question.

CC2340R5-Q1: Crystal cap_array tuning - Bluetooth forum - Bluetooth®︎ - TI E2E support forums

Many thanks,

Jesse

  • 0
    Prodigy 25 points

    Continues questions

    1. RF compensation is recommended open or close?

    2. The document says the RF compensation coefficient default depends on NDK crystal. If we need to choose another crystal, we need to ask our vendor for the coefficient right?

    Many thanks,

    Jesse

  • 0 in reply to ching jen Chuang
    TI__Intellectual 850 points

    Hi Jesse,

    1. 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.

    6. RF compensation is recommended to be turned on (checked on the sysconfig page)

    7. This is correct, there is a section on the sysconfig page where you can configure the coefficients of the crystal that you are using to better use the compensation feature.

    Best Regards,
    Cashmere

  • 0 in reply to Cashmere Ramos
    Prodigy 25 points

    Hi Cashmere,

    Thanks for the reply.

    For answer 3, we tested the board at room temperature (about 22℃); the RF Temperature compensation was off.

    For answer 4, Does that mean RF compensation is on and set at 25℃, and the crystal coefficient is based on the NXD?

    Many thanks,

    Jesse

  • 0 in reply to ching jen Chuang
    TI__Intellectual 850 points

    Hi Jesse,

    For answer #3, this is kind of expected if you are testing using SmartRF Studio since it was hardcoded at 25C. 
    For answer #4, may I clarify what do you mean by NXD?

    Best Regards,

    Cashmere

  • 0 in reply to Cashmere Ramos
    Prodigy 25 points

    Oh, that is NDK. I type it in error.