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ISOW7841: Does ISOW7841 iso power can support 4 pcs RS-485 device?

Jimmy WANG
Genius 3055 points
Part Number: ISOW7841
Other Parts Discussed in Thread: ISOW7741

Hi team,

Does ISOW7841 iso power can support 4 pcs RS-485 device?

  • 0
    TI__Guru 51940 points

    Hi Jimmy,

    Thank you for reaching out.

    Assuming that you are asking if the RS-485 bus at the SN75ALS176ADR bus pins can support connection of 4 RS-485 devices, I believe the answer is yes. Most RS-485 transceiver support connecting multiple devices on the bus. I can notify the team that supports SN75ALS176ADR to confirm on this.

    If I have misunderstood your question, then please elaborate your question on how you are looking to connect 4 devices so that I can answer your question better.

    ISOW7841 is our first-generation device family while we now have second-generation device ISOW7741 which offers significantly improved overall performance including radiated emissions performance. If customer is currently evaluating ISOW7841 for a new project then we recommend that they consider ISOW7741 for their design. Thanks.


    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    Genius 3055 points

    Hi Koteshwar,

    You may misunderstand. I mean the power supply capability of the IC. Due to the customer use four devices on secondary side.

    They want to know if the IC power supply capability is sufficient. ISOW has an integrated power inside.

  • 0 in reply to Jimmy WANG
    TI__Guru 51940 points

    Hi Jimmy,

    Apologies for the misunderstanding and thank you for the clarification.

    The output current of VISO pin on ISOW7841 is sufficient to power only one RS-485 transceiver when the total bus termination is 60Ω (120Ω + 120Ω). If customer RS-485 bus doesn't have any termination due to low number of nodes and shorter distances between them, then one ISOW7841 should be able to power 4 RS-485 devices.

    The max output current of ISOW7841 is 130mA when the device is operated in 5V input to 5V output configuration, customer can also consider this current and determine how many they can connect based on the RS-485 transceiver max current consumption.

    Let me know if this answers your question, thanks.


    Regards,
    Koteshwar Rao