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CC1200: Max Frequency Error

Aaron Spaete
Expert 4290 points
Part Number: CC1200

Team, 

My customer has the following questions. 

How do we determine the maximum frequency error can be tolerated before we lose bits/packets? It appears that the “Selectvity vs Offset Frequency” graph/figure on page 17 of the datasheet gives some clue of this, but it is just one case. In other words, is the following correct: if we have a 10MHz TCXO, with 10 PPM error (aging + FvT) that is 100Hz error at 10MHz.  Multiply that error by 91.5 (for 915MHz operation), we are at 9150 Hz error for the high band transceiver. For the error budget, we need to double this do to the TX and RX sides having independent errors.

 

On additional question,  is it true that a crystal oscillator preferred over a TCXO for the 40MHz clock? Why is that?

Thanks, 

Aaron

  • 0
    TI__Genius 11275 points

    Hi,

    Please see the App Note SWRA122D (CC11xx Sensitivity Versus Frequency Offset and Crystal Accuracy (although this is for the CC11xx devices the same principle of accounting for crystal frequency errors applies).

    TCXOs will provide a frequency accuracy that is tighter than a crystal can provide. However, TCXOs have a higher cost; it depends on the customer's requirements as to which is preferred. As many designs do not need a TCXO, most of our reference designs use a crystal to enable the use of lower cost crystals (but customers can of course use a TCXO instead).

    Regards,

    Zack