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LP87523-Q1: LP87523 CLKIN deterministic nature

Mathieu Stephan
Prodigy 30 points
Part Number: LP87523-Q1

Hello, 

For an upcoming project we're planning to use several LP87523 connected to the same power rail, and would therefore like to synchronize them together with a common phase shifted clock.

Extensively looking at the datasheet we however can't seem to be able to find about the deterministic nature of the clock synchronization feature.

Phrased differently: for a given clock signal, do we have the guarantee that the switching will always happen at the same moment regardless of the LP87523 internal state?

Thanks!

  • 0
    TI__Genius 10642 points

    Hi Mathieu,

    The LP87523 CLKIN pin allows for connection to an external clock, for such a scenario you are describing, although the nominal frequency should be between 1 MHz and 24 MHz. This can also be read in the datasheet by searching for the term 'clock', and also in section 8.3.2 on page 21 of the datasheet.

    Thanks,
    Field

  • 0 in reply to Field Tolson
    Prodigy 30 points

    Thanks! that's what I understood indeed.

    However that's not my question: is the "clock to mosfet switching time" delay deterministic?

    I want to make sure that if I use the same phase-shifted clock to multiple LP87523-Q1 then each LP87523-Q1 will switch at a different time.

  • 0 in reply to Mathieu Stephan
    TI__Genius 10642 points

    Hi Mathieu,

    If each LP87523 is connected to a ''different'' CLKIN signal, then they should switch with the difference according to their corresponding signal. Which I believe is what you are asking?

    If they are connected to the same CLKIN signal, then they should switch at the corresponding input signal. 

    Thanks,
    Field

  • 0 in reply to Field Tolson
    Prodigy 30 points

    Hello Field,

    Thanks a lot for your answer!

    My question is about the "should" in your sentence, I need this to be a certainty to make sure to be able to implement interleaving...

  • 0 in reply to Mathieu Stephan
    TI__Genius 10642 points

    Hi Mathieu,

    I apologize for any speculation that may have been implied, and did not mean to do so.

    Field Tolson said:
    If each LP87523 is connected to a ''different'' CLKIN signal, then they should switch with the difference according to their corresponding signal.

    TI specifies the devices to operate this way.

    Thanks,
    Field

  • 0 in reply to Field Tolson
    Prodigy 30 points

    Hello Field,

    Sorry for being persistent, but where in the datasheet do you see the relationship between the clkin and the internal mosfet control signal? I would expect a timing diagram of some sorts :)

  • 0 in reply to Mathieu Stephan
    TI__Genius 10642 points

    Hi Mathieu,

    No need to apologize. I do not know why the team did not include such a thing in the datasheet during initial testing or development, but perhaps the sync clock functionality section is meant to be visually descriptive but with no visual. 

    Thanks,
    Field