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Syncing an LMZ31506

David Burton
Expert 1330 points
Other Parts Discussed in Thread: LMZ31506

I have a system with many LMZ31506 regulators.  I need to sync them to an FPGA generated clock that remains low or possible floating until the FPGA is configured.

A problem I am having is that the regulators set at higher than 1.8V out will not start up to full voltage with the sync connected to the FPGA.  Since the supply will not come up fully the FPGA will not configure and the sync clock never starts and so there I am stuck.

If I disconnect the sync to the LMZ everything works fine.

How do you get around this problem?

Increasing the soft start to 5 msec seems to have some effect on the power up behavior, but does not fix this problem.

Thanks.

  • 0
    TI__Mastermind 28020 points

    Hi David,

    Can you send me the schemtic? You can send it to me directly at jarrigo@ti.com. Do you have any waveforms of the rails that do not start up correctly?

    Are you contolling the INH feature during start-up? Do you have the Rrt resitor populated for all LMZ31506 devices? What frequency are you synchronizing to?

    Thanks, Jason