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LMX2594: Unused pins

Mikhail Matusov
Intellectual 340 points
Part Number: LMX2594

Hello! The datasheet is not clear on what has to be done with the following pins if unused:

SYNC
SysRefReq
RampClk
RampDir
RFOUTBP
RFOUTBM

Can all of them be left open?

Thanks.

  • 0
    TI__Mastermind 27581 points

    Mikhail,

    Yes all can be left open.

    For RFoutBP/BM, you definitely want to leave these open as they are outputs.

    For SYNC and SysREFReq, you could ground them, but if you set INPIN_IGNORE=1, they are ignored.

    For RampCLK and RampDIR, they do nothing if RAMP_EN=0.

    So in summary, you could leave all these open and should definitely leave the RfoutBP/BM open.

    You could ground SYNC,SysRefReq, RampCLK and RampDir if you want to, but it is not necessary.

    Regards,

    Dean

  • 0 in reply to Dean Banerjee
    Intellectual 340 points
    Thanks Dean. I understand that the RFoutBM/BM are outputs but the datasheet says they need pullups. It should probably add "only when used". I also understand that the control inputs can be made irrelevant via registers, however my concern was whether there are electrical reasons why they shouldn't be left floating as, e.g., it might cause undesirable behavior in CMOS logic.