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DS91M040: Maximum Capacitive Load

Martin Seeger
Expert 5411 points
Part Number: DS91M040

Dear Team,

quick question regarding the DS91M040.

> What is the maximum capacitive load on multidrop bus for the DS91M040TSQ?

The device would run in a system with 100MHz square wave clock.

Thanks and best regards
Martin

  • 0
    TI__Mastermind 43795 points

    Hi Martin,

    This is a difficult question to answer with a specific number.  There are a few other important variables which determine the maximum rate of operation.

    1. Stub length ( for 100 MHz operation I recommend stub length < 12.5mm )

    2. Number of device loads (likely will be 10 or less)

    3. Density of device loads ( keep devices spaced at or greater than 2.5 cm apart )

    3. Termination location

    Do you have access to an IBIS tool like HyperLynx?

    The DS91M040 IBIS model would be the best tool to determine how this multi-drop bus will perform

    Regards,

    Lee

  • 0 in reply to Lee Sledjeski
    TI__Expert 5411 points

    Hi Lee,

    thanks for the swift reply and thanks for the hint for the IBIS mode.

    Below some feedback from the customer:

    1) Thanks for the hint!
    2) 7 devices = 1x TX and 6x RX
    3) Distance is expected to be 5...10cm
    4) Termination is placed at the end of the bus

    Best Regards
    Martin

  • 0 in reply to Martin Seeger
    TI__Expert 5411 points

    Hi Lee,

    I was wondering if you have more suggestions for the customer's use case?

    Thanks and best regard
    Martin

  • 0 in reply to Martin Seeger
    TI__Mastermind 43795 points

    Hi Martin,

    I think 6 device loads should run at 100 MHz with the termination at the end of the multidrop connection.

    It is always recommended to look at an IBIS simulation to help guide the solution. 

    Regards,

    Lee