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LSF0108: Pull up resistor

K.Hamamoto
Guru 12155 points
Part Number: LSF0108

Hi

I get confused about pull up resistor.On Figure at page 17,there is no pull up resistor at Vref_A side.

At the section 9.2.1.2.1, it is mentioned that it does not need the pull up rsistor if the master has the push pull output.

On the other hand,there is no any explain about what is the output type of this device at datasheet.So that, I understand as below.

   If the master (unidirection) is the open drain output , the pull up resistor need.

   If the master (unidirection) is the push pull output, the pull up resistor does not need.

   At the output of this device need the pull up resistor always.

Is my understanding correct?

Best regards,

Koji Hamamoto

  • 0
    TI__Guru 59750 points
    Hi Koji san,

    your understanding is correct.

    If the input to the LSF is pushpull ; i.e the line is able to go low and high from the output drivers, there is no need for pullup resistors.
    If the input to LSF is open drain i.e, the line is only able to go low on its own, but since internal PFET is missing, it is not able to maintain a high state, it would require pullup resistors to define the appropriate high level.
    The output of the LSF requires pullup resistors for up translation.

    Please watch the videos for more information on LSF translation.
    training.ti.com/tlm-lsf-intro