Hi CSR,
Can you eloborate the consequence of having an incorrect crystal trim?
What will be affected becasue of incorrect crystal trim - Range? Interference? Tx reliability? Rx Reliability? Certification?
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Hi,
Trimming of the xtal ensures the radio operates correctly, so a xtal that has poor ppm tolerance that is not trimmed will result in various issues as you've mentioned.
We recommend that all units be individually trimmed at the factory.
Incorrect Crystal Trimming may cause the signal to modulate outside the permitted band.
This would not pass the Bluetooth SIG RF testing.
Regards.
Noted. Thanks.
Having a module by third party will not need crystal trim, only need to make sure it is preserved during firmware update.
I highly recommend you confirm with the module partner that they actually have trimmed the xtal because some may take the 'easy' path and not trim the module's xtal. And if it is trimmed by the third party, there is an option when you do the fw upgrade to preserve the BT address and the xtal trim value as well.
Hi Liem,
Can we avoid the crystal trimming by using TCXO or 10ppm XTAL.
I read about this somewhere in older CSR forum.
Is this true ?
Regards.
Hi,
A TCXO is not supported with the CSR101x chipset family, only a xtal is supported. It is possible to get away without trimming if the xtal is better than +/-10ppm however you should definitely tune the external loading caps to ensure that it is set as close to the center value as possible, this will help with not needing the sw xtal trim. And it also depends on your end application as well. For CSRmesh applications, it is still highly recommend that you trim all xtal regardless of xtal tolerance.
Thanks for the response Liem.