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LSF0002: Could we use pull-down register?

Tsuyoshi Nogi
Intellectual 1970 points

Part Number: LSF0002
Other Parts Discussed in Thread: TXU0102, TXU0202

Tool/software:

Hi experts,

datasheet shows some schematics with pull-up resistor as following.

Could we change pull-up resistor to pull-down resistor?

If could, is there anything we should care? 

Thanks and regards,

Tsuyoshi

  • 0
    Guru 324800 points

    The LSF is a passive switch that allows only low-level signals to go through; high-level output voltages are generated by the pull-up resistors. Therefore, pull-ups are always necessary, and pull-downs do not make sense.

    If you do not need an auto-bidirectional translator, then a unidirectional device like the TXU0102/TXU0202 gives you more flexibility regarding all other paramers.

  • 0
    TI__Guru 57481 points

    Hi Tsuyoshi,

    I agree with Clemens' answer here- pulldowns are generally frowned upon when used with the LSF as the device itself is open-drain outputs. The output logic high signals will never fully reach VCC if pulldowns were used.

    Regards,

    Jack