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LMH1982: No lock indication of SD_LOCK

Part Number: LMH1982
Other Parts Discussed in Thread: LMP7711

Hello I have the strange problem reported here

Did anyone solve it or is it a bug? Thank you.

  • Did you try the suggestions in the other thread you linked, such as maximizing ICP1 to compensate for any leakage current due to VCXO input resistance and/or loop filter path, or maximizing the LOCK_CTRL value to relax the phase lock threshold?  It the VCXO input resistance is low enough to contribute enough leakage to introduce a phase error at the PLL1 PFD inputs, you may need to add an op-amp with high input impedance (like LMP7711) to buffer between the loop filter voltage to and VCXO input.