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DS90UB913Q-Q1: Internal pulldown value

Dan Ringger
Intellectual 1790 points
Part Number: DS90UB913Q-Q1

Hello - 

The datasheet says that the PDB pin has an internal pulldown, which means if PDB is not driven externally the DS90UB913Q-Q1 will be in shutdown mode.  I need to know what the value of that internal pulldown is, because I need the device to be "on" by default, but do not want to tie it directly to VDDIO (it's complicated, but there are circumstances under which I still want to be able to shut down or reset the DS90UB913Q-Q1 with PDB).  The DS90UB953 datasheet says 1M, but couldn't find anything for the 913.  Thank you

  • 0
    TI__Mastermind 18755 points

    Hello,

    I am currently looking into what the exact value is but it is going to be pretty weak similar to the 953.  What would be the reason that you need to know this?  It is recommended that a pull-up and capacitor be connected to this pin.  It is also possible to control the pin using a GPIO on some SoC which would allow you to control the device and doesn't need to be tied to VDD. 

    Regards,

    Nick

  • 0 in reply to Nicholas Darash
    TI__Intellectual 1790 points

    From Customer:  

    Thanks, that's probably info enough.  An older design of mine has it pulled up with a 10K, but I'm trying to have it controlled by a microcontroller output so that the micro can shut down or reset the serializer.  Problem is, I need it to default to the "active" state if the micro is reset because I need the FPDLink-III link to stay alive so I can send I2C traffic back-channel.  I think a 10K pullup and then using an open-drain micro output to yank it low if needed is probably the best solution.  I was just a bit concerned because I'd not noticed before that the 913Q had an internal pulldown, and I need to make sure my external pullup can overcome that.

  • 0 in reply to Dan Ringger
    TI__Mastermind 18755 points

    Hello again,

    So the 10k pull-up is definitely enough to pull it high and if the open drain output of the micro is high impedance while it is powered off then the system should work fine.

    Regards,

    Nick