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LMX2694-EP: Consecutive phase shift

Kazuhiko Hirano
Genius 11613 points
Part Number: LMX2694-EP
Other Parts Discussed in Thread: LMX2572EVM

Hello,  

Datasheet 7.3.13 states “If a SYNC pulse is sent (software or pin) or the MASH is reset with MASH_RST_N, then this phase shift is from the initial phase of zero. If the MASH_SEED word is written to, then this phase is added.”.
Here, my customer has a question.
After the initial phase of zero, can the phase be varied continuously by writing various MASH_SEED values continuously without another SYNC pulse or a MASH reset? Or, before changing the phase, SYNC pulse or a MASH reset is always required first?

Best regards,

K.Hirano

  • 0
    TI__Guru* 81580 points

    Hi Hirano-san,

    After SYNC, the reference clock and RF output will be phase aligned with some deterministic delay. This delay can be compensated with phase adjustment with MASH_SEED.

    So you should, first of all, perform a SYNC without MASH_SEED (= 0). After SYNC, put some value in MASH_SEED to change the phase. For example, if you program 100 in MASH_SEED, the phase will change according to this value. If you program this register (R41) again with the same value, the phase will change one more time. The total phase change is 2 x phase of MASH_SEED = 100. Please read LMX2572EVM user's guide section 3.2.1 for an example.

  • 0 in reply to Noel Fung
    TI__Genius 11613 points

    Noel,

    Thank you for your response.
    I understood how to increase the phase shift.
    But are there any ways to decrease the phase shift?

    Best regard,

    K.Hirano

  • 0 in reply to Kazuhiko Hirano
    TI__Guru* 81580 points

    Hi Hirano-san,

    No, the phase adjustment will only move forward. You can add multiple forward adjustments until the next cycle is behind the reference.