LMX2594: Phase Offset for ADC Interleaving applications

Thomas Lam

Part Number: LMX2594

HI I would like to use two LMX2594 to drive two ADCs for interleaving applications. Is there a easy way to configure the LMXs using TICS PRO to have 180 degree phase with each other?

over 5 years ago

0 Dean Banerjee over 5 years ago

TI__Mastermind 27581 points

Thomas,

As these are differential outputs, it would seem the easiest thing to do is just swap the outputs.

There is no software bit to swap polarity, but you could do this in your layout.

If this doesn't work, you can use the SYNC feature and MASH_SEED bit to program in a delay of 180 degrees as well.

Regards,

Dean

0 Thomas Lam over 5 years ago in reply to Dean Banerjee

Prodigy 50 points

Thanks Dean. The LMXs are already attached to the ADCs on the board and I don't want to hack up the board to swap the outputs. Maybe you can elaborate a bit more on the SYNC feature and MASH_Seed bit to program in a delay of 180 degree? Thanks again.

Thomas

0 Dean Banerjee over 5 years ago in reply to Thomas Lam

TI__Mastermind 27581 points

Thomas,

This is outlined in more detail in the datasheet, but the basic idea is this:
1. Put the device in SYNC mode by setting VCO_PHASE_SYNC=1
2. Go to page 26 of the datasheet and use
Phase shift in degrees = 360 × ( MASH_SEED / PLL_DEN) × ( IncludedDivide/CHDIV )
3. So for instance, if you have an output frequency of 5 GHz, then
Fvco = 10 GHz
CHDIV= 2
IncludedDivide = 4
Choose PLL_DEN = 4
Choose MASH_SEED = 1
Then:
180 degrees = 360 × ( 1/ 4) × ( 4/2 )

I encourage you to play with our TICSPro software as it gives a lot more help setting this up.

Regards,
Dean

0 Thomas Lam over 5 years ago in reply to Dean Banerjee

Prodigy 50 points

Thanks Dean. Really appreciate your help and information.

Regards,

Thomas

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LMX2594: Phase Offset for ADC Interleaving applications