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TXS0108E external pull-up spec

Johnny Lau
Intellectual 2465 points
Other Parts Discussed in Thread: TXS0108E

Team,

Customer wants to use the TXS0108E for an MDIO level shift from 1.2V to 2.5V.  They 2.5V side is an unknown connection from an external source and will have a pull-up on that side.  What is the lowest value pull-up that we can tolorate?  Can a 1ku be used on the 2.5V side?

Also, for example if there is a 1ku pull-up on the 2.5V side do you also need the same value pull-up on the 1.2V side?

Speed is 1Mb's and ideally they would like 4Mb/s but if they need to always be 1Mb/s than that is ok.

Volume is ~ 100ku and this MDIO is becoming a common need we should look into.

 

 

  • 0
    TI__Genius 9085 points

    Johnny,

    A 1kOhm resistor can be used on the 2.5V side if the driver can pull enough current through the parallel 1kOhm and internal 40kOhm resistances to drive the line low.

    So, for 2.5V, and 975Ohm this is 2.6mA.    You do not need the same size pull-up on the other side.

    Speed is heavily dependent on the loading of the line. Is MDIO an open drain driver application?