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TLIN1029-Q1: Why LIN master has 1k pull up and slave has 30k pullup?

DAYYAN SHERIFF
Prodigy 20 points
Part Number: TLIN1029-Q1

Why do we need use 1k pull up for master and 30k pull up for slave.

  • 0
    Guru 316690 points
    Because the LIN specification says so.

    LIN uses an open-drain line, so it needs to be pulled up to get a valid high-level voltage. The pull-up resistor needs to be small enough so that rising edges are fast enough, and large enough so that no power is wasted. The 1 kΩ value is chosen so that these parameters are correct for the LIN protocol.

    There needs to be exactly one 1 kΩ pullup on the bus, and there is exactly one master, so that is the obvious place to place it. (In theory, it could be placed anywhere else on the bus.)

    The 30 kΩ resistors at the slaves just ensure a valid voltage level if the connection to the master is broken. (Note: the TLIN1029-Q1 has an integrated slave resistor.)