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Original question:

ISOW1432: ISOW1432 VISOOUT power supply

ISOW1412: Supports an external load of 50mA when RS-485 bus has no termination

KrnB
Intellectual 640 points
Part Number: ISOW1412

Hello,

My application has only 2 devices on RS485 bus (bus has no termination). But I need to power external load of 50mA worst-case.

I see that ISOW1412 only provides 20mA for external loads while it powers RS485 bus.

Though my requirement of external load current is higher, my application's RS485 bus will only consume less than 1mA. Can ISOW1412 work for my application ? 

  • 0
    TI__Guru 55815 points

    Hi KrnB,

    Thank you for reaching out and seeking clarification regarding external load support.

    Since you do not have a termination resistor on RS-485 bus, the VISOOUT of ISOW1412 can support an external load upto 50mA without any issues. Let me know if you have any further questions, thanks.


    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    Intellectual 640 points

    Thank you for prompt response. It looks like the limiting factor for current drawn from VISOOUT pin is not fixed as 20mA but it depends on the overall load on VISOOUT regulator. 

  • +1 in reply to KrnB
    TI__Guru 55815 points

    Hi Karan,

    Yes, your understanding is correct that the 20mA is not a fixed limit rather this is what we believe the device is capable of supporting in addition to standard RS-485 load. When RS-485 is not loaded/terminated, VISOOUT can take that additional load in place of the RS-485 termination. Thanks.


    Regards,
    Koteshwar Rao