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LMX2594EVM: Initialization sequence duration

user5941540
Intellectual 280 points
Part Number: LMX2594EVM
Other Parts Discussed in Thread: LMX2594

We are developing a new electronic board using LMX2594 PLL component. We need to minimize SPI initialization sequence duration, in order to meet a board requirement.

Here are SPI initialization sequence we use to program this PLL:

  1. R0 register programmed with 2512 (reset=1)
  2. Wait X ms
  3. R0 register programmed with 2510 (reset=0)
  4. Wait X ms
  5. All registers programmed (R0 with 2514 (FCAL_ENABLE=0)
  6. Wait X ms
  7. R0 register programmed with 2518 (FCAL_ENABLE=1 and MUXOUT=0)
  8. Wait X ms
  9. R0 register programmed with 251C (FCAL_ENABLE=1 and MUXOUT=1)

 

If X=4ms, everything is OK (PLL is locked and output signal frequency is correct). If X=2ms, PLL locks for few ms and then unlocks.

 

Do you know what is the minimum temporizations required between each step of the sequence described above ?

 

Thanks a lot for your help,

Regards

  • 0
    TI__Guru** 111060 points

    Hi There,

    I have some questions.

    1. R0 register programmed with 2512 (reset=1) [TI] Is the reference clock ready before this step?
    2. Wait X ms [TI] I don't think this step is required, the RESET is to return all the registers in the default values, it will take virtually no time.
    3. R0 register programmed with 2510 (reset=0) [TI]FCAL_EN = 0?
    4. Wait X ms[TI]same as 2. above.
    5. All registers programmed (R0 with 2514 (FCAL_ENABLE=0) [TI]Make sure program the register in descending order. That is, program R0 at the end. I suggest make FCAL_EN = 1 in this step to start calibration.
    6. Wait X ms
    7. R0 register programmed with 2518 (FCAL_ENABLE=1 and MUXOUT=0)[TI]If you do not do register readback, you can make MUXOUT = 1 in this step and skip step 8. and 9.
    8. Wait X ms
    9. R0 register programmed with 251C (FCAL_ENABLE=1 and MUXOUT=1)
  • 0 in reply to Noel Fung
    Intellectual 280 points

    Hi Noel,

    I would like to thank you for the answer, my colleagues took into account your remarks and everything works for them.