LMK04821: Phase Frequency Detector?

Derek de Jager

Part Number: LMK04821
Other Parts Discussed in Thread: LMK04828

Hello,

Just a question - are the phase detectors in the LMK04821 (and LMK04828) phase-frequency detectors or just phase detectors? ie. will the loop frequency lock (sweep to the correct frequency due to charge pump DC output bias) or does the frequency have to be close enough to be captured by the loop using only a phase detector?

Thanks,

Derek

over 2 years ago

0 Julian Hagedorn over 2 years ago

TI__Mastermind 20900 points

Hi Derek,

the parts have a phase frequency detector build in. However, you will need to make sure that your R and N dividers are set properly. In that case the input signal can be off by the VCXO pulling range to still achieve lock.

regards,

Julian

0 Derek de Jager over 2 years ago in reply to Julian Hagedorn

Prodigy 10 points

Thanks Julian,

I was just checking because we had advice from TI to lock the loop voltage to midrail and then release to aid locking.

Thanks,

Derek

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LMK04821: Phase Frequency Detector?