LMX2594: Use of Pre and Post R divider with SYNC

Josh Merti

Part Number: LMX2594

Are there any limitations on using the Pre and Post R dividers on OSCin as long as the OSCIn frequency is less than or equal to 100 MHz? Does it have any effect on the SYNC category of the design? For example, using a 100 MHz OSCIn frequency but then using the dividers to use 25 MHz as the Fpd and an output frequency of 3750 MHz (N of 75, divider is 4 since it's SYNC mode) am I still in Category 1 -- SYNC mode required but no pulse/software necessary?

over 4 years ago

0 Noel Fung over 4 years ago

TI__Guru** 108550 points

Hi Josh,

As we can see from the flow chart in Figure 27 of the datasheet, the Sync Cat. does not depend on fpd.

In this case, the output frequency is not an integer multiple of the OSCin frequency, so it is Cat. 3 Sync.

You can use TICS Pro to determine the Sync Cat.

0 Josh Merti over 4 years ago in reply to Noel Fung

Prodigy 190 points

So even though the fundamental output of the VCO is a multiple of Fosc it's Category 3?

0 Noel Fung over 4 years ago in reply to Josh Merti

TI__Guru** 108550 points

Hi Josh,

Yes, this is possible as we care the output frequency rather than VCO frequency.

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LMX2594: Use of Pre and Post R divider with SYNC