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THVD1420: THVD1420 output current is smaller than ADI device

Jiandong Liu
Intellectual 1801 points
Part Number: THVD1420


Hi expert,

I recommend my customer to use THVD1420 to replace ADM3485EARZ. However, the output current of THVD1420 is much smaller than ADM3485EARZ. Could you please comment:

1. Is there any risk if using THVD1420 to directly replace ADI?

2. Do we have any device with larger output current?

Thanks.

THVD1420:

ADM3485EARZ:

Regards,

Jared.

  • 0
    Guru 318030 points

    The RS-485 specification requires that a driver is able to generate a voltage drop of 1.5 V over a 54 Ω load. Both the ADM3485E and the THVD1420 meet this requirement.

    The RS-485 specification requires that the short-circuit current does not exceed 250 mA. Both the ADM3485E and the THVD1420 meet this requirement. (It's |IOS| in section 5.7 of the THVD1420 datasheet.)

    The THVD1420 datasheet specifies that the recommended maximum output current is 60 mA (which corresponds to a load much smaller than 54 Ω). The ADM3485E datasheet does not specify this value; its implied maximum is the 27.8 mA over the specified 54 Ω load.

  • 0
    TI__Guru 52652 points

    Hi Jared,

    Clemens is correct. Those are two different specs ADI device spec is the short circuit current (what happens when the differential bus shorts) which isn't the same as the standard differential current. Both devices would be RS-485 compliant and should work in the same applications. RS-485 under normal conditions isn't likely to be passing that much current (regardless of the device - the application generally doesn't call more that much current as Clemens alluded to.)

    Please let me know if you have any other questions!

    Best,

    Parker Dodson