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LMH1983 holdover at 0v

Gilles Chouinard
Prodigy 10 points

Hi,

I have an issue with the VC(VCXO control voltage) going to zero when going from genlock to holdover when the REF is disconnected (LOR mode set to holdover). It happens in a particular sequence of events. I traced the problem to the fact that, when the REF is connected, VC abruptly goes to zero for 200 ms before ramping up to the mid-value of 1.6v. If REF is disconnected during this period, the holdover voltage will be zero.

Can I prevent the VC from going to zero for a brief period when the REF is connected?

All the registers are at their default values, except reg 5=0x2B.

 

  • 0
    TI__Guru* 93670 points

    Greetings,

    I appologize since i just came across this post.

    I use SD1983 Evaluation board in this mode and was able to genlock with no problem. However, i am not sure how you get VC to drop. Any sequence you perform to get the VC to drop ?

    Regards,,nasser