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ISOW1432: protection against 24V

Isee
Expert 6760 points
Part Number: ISOW1432
Other Parts Discussed in Thread: THVD2410, ISOW7741

I would like to protect the bus (RS-485 A/B) not only against transiensts but also 24V if the customer accidentally applies a voltage there. 

According to datasheet only -12V to 15V are ok.

What happens/can happen if you apply 24V?

How can the pins be protected?Do you have a proposal?

Regards

Andreas

  • 0
    TI__Guru 55885 points

    Hi Andreas,

    Thanks for reaching out.

    If a transient exceeding device rating is applied to RS-485 bus, then a TVS diode can be used to suppress the transient and protect device. But a short 24V DC is going to be a continuous event and protection components like TVS diodes won’t be able to withstand such a stress. The best way to protect against such events is to choose RS-485 devices that are rated for 24V.

    There are non-isolated RS-485 transceivers like THVD2410, you could use ISOW7741 with the non-isolated RS-485 THVD2410 to meet this requirement. No additional protection components are needed to meet your requirement.

    An alternate approach is to use suitable PTC & SIDAC combination on RS-485 bus to protect against sustained voltages. Please see below snapshot and link to the reference design that that implements these protections.

    https://www.ti.com/tool/TIDA-060027


    Regards,
    Koteshwar Rao