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problem about nRF52832's bluetuth

i have question about nRF52832's bluetuth. xtal is 32M, Cload  is 12pf, but the frequency is 2.402199G(tested by Network Analyzer),  Frequency differency is 199K.  We find that bluetuth may disconect;  Disconnect is individual problem, not common problem. Pout is 1.9dbm, We can't fix it.  what should i do next? 

schamtic:                                                                                                            

layout:

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  • Hi,

     

    A frequency offset of 199 kHz is 82.8 ppm offset, which is quite a lot.

    It sounds like the capacitors does not match the "CL" of your crystal (the CL is per your requirement, Digikey has 32M FA128 crystals with CL of 8, 10, 12, and 18 pF).

    The formula is:

    C = 2*CL - Cpin - Cpcb

    Where Cpin = 4 pF, and Cpcb is normally 0 - 2 pF, depending on the PCB track length.

     

    Your capacitors of 12 pF indicates then a "CL" of 8 pF on your crystal part. Can you please double check what the "CL" of your crystal is?

     

    Best regards,

    Håkon

Reply
  • Hi,

     

    A frequency offset of 199 kHz is 82.8 ppm offset, which is quite a lot.

    It sounds like the capacitors does not match the "CL" of your crystal (the CL is per your requirement, Digikey has 32M FA128 crystals with CL of 8, 10, 12, and 18 pF).

    The formula is:

    C = 2*CL - Cpin - Cpcb

    Where Cpin = 4 pF, and Cpcb is normally 0 - 2 pF, depending on the PCB track length.

     

    Your capacitors of 12 pF indicates then a "CL" of 8 pF on your crystal part. Can you please double check what the "CL" of your crystal is?

     

    Best regards,

    Håkon

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