nRF52832 32 MHz Crystal Aging – Epson FA-128

[Ron]

Hi

I use Epson FA-128 (Q22FA12800025) based on Nordic’s recommendation, but I’m struggling to compare alternatives because the datasheet lists two aging rates:

±1 ppm/year for RF reference

±5 ppm/year for clock applications

Does Nordic assume the 1 ppm RF spec, or is aging expected to be higher? I am not sure how can the application effect the ppm like that.

I’m considering a ±3 ppm/year alternative—will this have a significant effect on meeting BLE accuracy requirements over the product’s lifetime?

Thanks!

[Simonr]

Hi

To accommodate for aging rates, we generally recommend going for crystals with a better frequency tolerance than what's the minimum according to the PS. In the nRF52832 PS the HFXO frequency tolerance for BLE applications should not be more than ±40ppm. If you go for a ±10ppm frequency tolerance rated crystal, you make sure that even with ±5ppm per year of drift it takes many years before breaching with these specs. The recommendation would be to go with what Epson recommends for RF reference, but I think you should be fine with I.E. a ±3ppm aging.

Best regards,

Simon

[Ron]

Hi Simon

My question is about comparing and understanding the Q22FA12800025 spec when comparing to the alternatives, so when the Q22FA12800025 states 1 ppm for RF and 5 ppm for Clock aging per year, what I am supposed to take as the actual aging? is the tolerance 10ppm or 30 ppm? what do you assume it is?

I know that I will be OK with 3ppm, but if we have 1ppm now, it does mean, that the with the alternative the product will preform a few years less overall

Thanks!

[Simonr]

Hi

To be on the safe side you should always assume the worst numbers from the spec. but you can always contact the vendor to get an "official" statement on it I think. If not, the safe play would be to assume the 5ppm aging.

Best regards,

Simon