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LMH1983 Drift Clock

Newton
Expert 1125 points
Other Parts Discussed in Thread: LMH1983

1.    Would like to use drift lock to sync up to the input reference. Is drift lock applicable only during a loss of the same input reference?

2.    The LMH1983 datasheet has a typo on page 14. Can you please clarify the functionality of TOF1_Sync_Near and TOF1_Sync_far?

 

 

 

 

  • 0
    TI__Genius 13475 points

    1.  The drift lock feature can be used at any time, so for example if the device is running in free run mode, and then a reference is applied, drift lock can be used to gently bring the TOF signal into alignment with the Vsync input.  You should note however, that under this condition it may take a long time to bring the signal into alignment, and during this time, the clocks will not be locked to the HSYNC input - it may take several minutes for the device to achieve lock in this mode.

     

    2.  I will make edits to the datasheet to try to make this more clear.  The device can be programmed to have different behaviour depending on how far out of alignment it is, and this is what TOF1_Sync_Near and TOF1_Sync_Far are controlling.   If the TOF1 signal is within 2 video lines of the VSYNC input, then the lock behavior described in bit 3 of address 11h is used, if it is more than 2 video lines away, then the behaviour described with bit 4 is used.  This allows you to use drift lock if it is not too far out of sync, but to crash lock if it is too far away.