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CC1350 868 MHz frequency error

Caglar Ivriz
Prodigy 70 points
Other Parts Discussed in Thread: CC1310, CC1350

Hi,
We have designed our custom board with CC1350 using TSX-3225 24.0000MF15X-AC3 10 ppm crystal. While testing its RF performance at 868 MHz, we figured out that CC1350 RF Core transmits signal at 867.917 MHz by the help of spectrum analyzer. In our last design before this, we had used CC1310 with the same crystal, and did not experienced this problem. How can we solve this issue, except calculating each board's frequency error and setting frequency values with offset?
Any help will be greatly appreciated.
Thanks,
Caglar

  • 0
    TI__Guru**** 317180 points
    If you have programmed the radio to send at 868.000 MHz and you measure 867.917 MHz this means that you have a 83 kHz frequency offset. This is larger than what normally could be explained by layout changes. We have seen before that customers by accident have used a crystal with higher CLoad than we have used in the reference design. Could you confirm the Cload for the xtal you have used?
  • 0 in reply to TER
    Prodigy 70 points
    Thank you, it worked like a charm. We have checked the board and realized that DNP capacitors had been assembled during manufacturing. After removing them, the problem is solved.