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ISO7720: Load Capabilities

Jason Lamb
Prodigy 60 points
Part Number: ISO7720
Other Parts Discussed in Thread: ISO1500, ISO1410

What is the max load that this isolator can drive into? The datasheet shows an example load of 15pF, what cable does this represent? 

  • 0
    TI__Genius 17100 points

    Hi Jason,

    Thank you for posting, and welcome to E2E!

    The ISO77xx family of isolators should be configured to output a recommended current of up to 4mA in systems. This applies to all operating conditions.

    "Low capacitance" cables typically have capacitances of 12 - 16pF/ft, however the switching characteristics of this device are defined for 15pF loads since cables of various lengths, types, and terminations can be configured to <15pF values.

    Which cable are you interested in using?


    Respectfully,
    Manuel Chavez

  • 0 in reply to Manuel Chavez
    Prodigy 60 points

    Hi Manuel,

    We are trying to drive a wiegand output through this isolator  and into a receiver. The end user will be responsible for cable selection but in most cases will be using a phoenix 5-conductor M12 CAN cable. The cable length will be in the 10-100 ft range. Is this isolator capable of driving into this cable?

    Thanks for your help,

    Jason 

  • 0 in reply to Jason Lamb
    TI__Mastermind 49445 points

    Hi Jason,

    ISO7720 accepts and outputs single-ended CMOS logic inputs/outputs and such logic signals are typically limited to traces on PCBs. Whenever there are cables and longer communications distances are involved, differential communication interfaces like RS-485 and CAN are used.

    If you require communication in the range of 10-100 ft then I recommend using RS-485 transceiver on both ends of the cable. If you require isolation as well then you can use isolated RS-485 device. ISO1410 and ISO1500 are two of our latest isolated RS-485 transceivers that offer best overall performance. Let me know if this is something you would like to use. Thanks.

    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    TI__Mastermind 49445 points

    Hi Jason,

    Hope my inputs have answered your questions. I will go ahead and mark this as closed, if you do have any question then you reply to this E2E thread. Thanks.

    Regards,
    Koteshwar Rao