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TXB0104: Use of TXB familly with component with internal pullups

Giuliano FRANCHETTO
Intellectual 380 points
Part Number: TXB0104
Other Parts Discussed in Thread: SN74LVC125A

Hi,

We need to shift a bunch of 3V signals to 1.8V.

We first chose to use the TXB family to do, but the component connected to the low power side (VCCA) has internal pull-ups ont its IO line.

The internal pullups are 11k resistors, which are below the 50k recommended limit.

Would the TXB work in this condition? If not, how could I fix the issue?

Regards

Giuliano

  • 0
    Guru 317450 points

    This will not work. To allow automatic bidirectional level shifting, the TXB has weak outputs buffers, which might not be strong enough to override those pull-up resistors.

    For unidirectional downshifting, use a plain buffer with overvoltage-tolerant inputs, e.g., the SN74LVC125A.