problem about nRF52832's bluetuth

[visionwang]

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:

[Håkon Alseth]

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

[visionwang]

crystal's  part number is FA-128 32.0000MF10Z-AJ3 ,Cl is 8pF 

[Håkon Alseth]

Your crystal loading seems to be correct.

 

Q1: How many devices are showing this issue?

Q2: Does all devices have the same offset?

Q3: Have you tried replacing the crystal to see if this issue is then fixed?

Q4: Are you testing with a unmodulated carrier (for instance by using radio_test in SDK v14) ?

 

Best regards,

Håkon

[visionwang]

Q1: only one device has this issue;

Q2: yes,all devices have the same offset;

Q3: yes,i do, but the issue doesn't disappear,  not only replacing the crystal, but also replacing other components , such as Cl,nRF52832,antenna,and so on

Q4: no, how can i get SDK v14?  what is the purpose?

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