• Resolved

LMX2594: asynchronous SYNC pulse

Expert 4765 points

Replies: 3

Views: 54

Part Number: LMX2594



My customer would like to align RFoutA and RFoutB phase using SYNC at Category 3 condition.

They do not care about absolute delay from OSCin to RFoutA/B, thy care about only phase alignment between RFoutA and RFoutB.


Instead of keeping specific tSETUP and tHOLD between SYNC and OSCin, they would like to use an asynchronous SYNC pulse having two OSCin frequency cycle width.

If the 1st OSCin rising edge misses due to not enough tSETUP, the 2nd OSCin rising edge can get SYNC with good enough tHOLD because SYNC pulse width is two OSCin clock cycle.


Can they get aligned RFoutA and RFoutB phase as they expected with the two OSCin cycles asynchronous SYNC pulse?


Best regards,



  • Hirano-san,

    RFoutA and RFoutB are always in SYNC as they share the same divider.

    Perhaps the customer was thinking there were separate dividers, but this is not the case.

    You can have one output without divider and one with divider, but still in this case, the outputs will be inherently in SYNC

    For the case that RFoutA is divided and RFoutB is SysRef, these are based on the same channel divider.

    SO in summary, I do not think that they need SYNC at all.

    SYNC is for creating deterministhc delay between OSCin and RFout.


  • In reply to Dean Banerjee:



    Thank you for your response.


    But, I am confused.

    Looking at datasheet figure 25, phase between RFoutA and RFoutB are not aligned before SYNC pulse but it gets aligned after t1 + t2 from SYNC pulse.

    Do you mean the figure 25 is wrong?


    Anyway, both RFoutA and RFoutB are from channel divider and their frequency is the same in my customer case.

    So, they do not really need to do anything at all to get aligned phase between RFoutA and RFoutB?


    Best regards,



  • In reply to Kazuhiko Hirano:

    Hello Hirano,

    The image above is showing SYNC between two devices. You are asking about RFoutA and RFoutB within the same device.

    Within the same device RFoutA and RFoutB are always in SYNC.