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SN74CBTLV3257: Select line floating

panzer
Prodigy 10 points
Part Number: SN74CBTLV3257
Other Parts Discussed in Thread: SN74CBTLV3126

Tool/software:

Hi,

Just need to know if the Select input can be left floating. We have the select input controlled by a fpga. Is a pullup/pulldown recommended on the sel line to set a default option?

  • 0
    TI__Mastermind 35618 points

    Hi Panzer,

    The select line can't be left floating, otherwise you won't know the state of the device and won't be able to control it. 
    Why are you leaving the select pin floating? The device has 1 select pin so it doesn't make sense to not utilize it. 
    If you want to tie it permanently high or low, which one you should do will depend on the functionality you're aiming to achieve. Do you want the A port to only be connected to B1 or do you want it only connected to B2. If you tie Select high or low, bare in mind you will not be able to switch between B1 and B2 though. If that's the functionality you want to achieve though, I would recommend a different device. You would be looking for a 4ch 1:1 instead, which we have some options (SN74CBTLV3126 for example)

    Thanks,
    Rami

  • 0 in reply to Rami Mooti1
    Prodigy 10 points

    Sorry I should've been more clear.
    The Select line is connected to a FPGA io pin and can be driven high/low to switch between the channels. 
    My question was more along the lines of does the select line need a default state (either pulled up or pulled high) when FPGA isn't programmed yet. But this has been solved since posting. Thank you for your response.