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Hi,
I have an issue with 1-pps ZDM which takes more than 1 hour to get that. I am using 1-pps lock to DPLL3, and APLL3 lock with 48MHz TCXO with 96MHz PDF. OUT0 is 1-pps out with ZDM. OUT4 and OUT5 are 156.25MHz with PLL3 as an output source. Without ZDM mode enabled, it took less than 10 min of lock time. But once ZDM mode enabled, it took more than an hour to get it locked. I was wondering if this is normal for ZDM mode. If not, can you please send me information to try to shorten that up? Or, if you have a TicsPro file that I can try, please provide one. Here are my screenshots that I am currently using.
Thank you.
Youngho
Hi Youngho,
Can you please share the .tcs you used with 1PPS + ZDM that gets 1 hour lock time?
Regards,
Jennifer
Hi Jennifer,
This file is more representative to the screenshots sent earlier. Both will work but use this one if possibile.
Thanks
Youngho,
Jennifer is currently out of office. Please expect a response by Monday.
Thanks,
Kadeem
Hi Jennifer,
I wonder if you had tried the 1-pps ZDM with shorter lock time. Can you please let me know about it?
Thanks,
Youngho
Hi Youngho,
The 1-hour lock time is expected for 1-PPS because it requires a narrow DPLL LBW (1/TDC in this case it is 0.01 Hz or 0.1 Hz). This means the updates to the TDC and APLL numerator are much slower which causes longer lock times.
Regards,
Jennifer
Hi Jennifer,
We had about 5-10min lock time for the 1-pps. But when ZDM engaged, it took ah hour to lock. Do you have any idea how to reduce lock time with ZDM enabled? Do you have any tips or user cases that uses ZDM with shorter lock time? 1-hour lock time is useless for the system in any situation. This might be the last gate that I need to solve for the LMK5B33216 usage for my system. Please help this out.
Thanks,
Youngho
Youngho,
We do not recommend 1-PPS + ZDM combination because of the delayed lock times. If the 1-PPS goes out then comes back, the DPLL may not be able to recover it when ZDM is enabled and could fail to lock again.
Regards,
Jennifer