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Original question:

LMK04828: Device Register Programming

LMK04828: LMK04828: Device In Bypass Mode

Hassen Basha1
Prodigy 160 points
Part Number: LMK04828

I want to use the LMK04828 sysref generation in bypass mode through sync pin.

If i use sync pin for sysref in bypass mode , the outputs clocks will be resetted when i apply sync input ? If resetted whether output clocks will be in sync ?

What is time requirement for bypass mode to normal mode changing?

  • 0
    TI__Mastermind 33710 points

    Hello Hassen,

    The SYNC/SYSREF path is shared, and used for both synchronization and for SYSREF generation. The SYNC/SYSREF distribution path is connected to muxes (SYNC_DIS0, SYNC_DIS2, etc. and SYNC_DISSYSREF) which gate the divider reset for clock synchronization. If the SYNC_DISx bit for a channel is set, signals on the SYNC/SYSREF distribution path will not reset dividers.

    What do you mean by "bypass" and "normal" mode? For bypass, do you mean using the SYNC pin as a SYSREF request pin?

    Regards

  • 0 in reply to Derek Payne
    Prodigy 160 points

    Hi Derek Payne,

    Thank you for reply.

    Bypass mode means SYNC pin as a SYSREF request pin. Normal mode means LMK normal operation.

    Please provide timing for Sync pin to sysref request generation.

  • 0 in reply to Hassen Basha1
    TI__Mastermind 33710 points

    Hello Hassen,

    Thanks for answering my question. I recommend at least 4ns setup time to SYSREF request pin both for generating SYSREF signal and for terminating SYSREF signal. We don't currently have timing from SYNC pin to SYSREF output generation specified in the datasheet, so for now this is a conservative guideline and should not be treated as a datasheet guarantee. If you have room to increase the setup time to >4ns, please do.

    Regards,