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VCO selection on CC430 and CC1110

pmaheral
Prodigy 60 points

I'm working with a CC430 and a CC1110 in the 900MHz band using manual calibration.  From design note DN508, it says that above 861MHz, I need to disable VCO selection during calibration, and choose the high VCO.    Below 861MHz, TEST0.VCO_SEL_CAL_EN = 1; above 861MHz, TEST0.VCO_SEL_CAL_EN = 0 and FSCAL2.VCO_CORE_H_EN = 1.

The cc430 user guide says that recommended setting for TEST0.VCO_SEL_CAL_EN changes with frequency, and that SmartRF Studio should be used to determine the correct settings before doing a calibration.  Following this suggestion, I ran SmartRF Studio 6.13.1.0 to verify my settings.  If I select a CC1110, I see that TEST0.VCO_SEL_CAL_EN changes from 1 to 0 above 861MHz as expected.  However, when I select the CC430, TEST0.VCO_SEL_CAL_EN changes from 1 to 0 above 863 MHz, not 861MHz.  I thought that the two devices (CC1110 and CC430) used the same radio, so I am left wondering what threshold I should use to determine if VCO selection should be enabled or disabled during calibration.  Please note that I am using common source code for the calibration of these two devices and would like to keep it that way.

I also tried SmartRF Studio 7.1.2.3 for "another opinion", but it appears to be broken with respect to that register/bit (TEST0.VCO_SEL_CAL_EN) since it does not change for either device regardless of frequency.

 

  • 0
    TI__Mastermind 39860 points

    CC430 and CC110 use the same radio so the VCO selection should therefore be identical. Apparently we are using different threshold for CC430 (863 MHz) and CC1110 (861 MHz) in SmartRF Studio. You can set the threshold to 861 MHz for both devices. However, in Europe the lower operating frequency is limited to 863 MHz so you will have no issue in any case. Use TEST0.VCO_SEL_CAL_EN = 0 and FSCAL2.VCO_CORE_H_EN = 1.

  • 0 in reply to Sverre
    Prodigy 60 points

    We have been using the automatic selection regardless of frequency, and haven't noticed any problems.  Maybe the automatic selection is selecting the high VCO correctly, but I can't be sure without further testing.  I will use a threshold of 861MHz if we start to notice any problems with the calibration.