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ISO1450: Replacement for IL485E

Okutsu
Prodigy 190 points
Part Number: ISO1450

Tool/software:

Hi Team,

Our customer is considering replacing their NVE IL485E with an ISO1450DW and would like to know if there are any concerns regarding this.

Reason for device selection
In a field environment where the communication idle time potential is about 30mV,
IL485E
Positive input threshold voltage max: 200mV
Negative input threshold voltage min: -200mV
In this environment, it is in an undefined range and communication is not possible.

In contrast,
ISO1450DW
Positive input threshold voltage max: -10mV
Negative input threshold voltage min: -200mV
By putting the communication idle time potential outside the undefined range, communication is improved, so this device was selected.

Terminal 10 of the IL485E is not used, so there are no problems with functionality.
Could you please let me know if you have any other concerns regarding this replacement?

Best regards,

  • 0
    TI__Mastermind 22345 points

    Hello Okutsu, 

    Thank you for reaching out. ISO1450 would be a good fit for this application with the smaller intermediate range.  30mV does not leave a lot of margins from the VIT+ spec and could lead to potential errors in the real application. Please keep in mind that standard RS-485 communication thresholds are +/-200mV according to the standard. However, the ISO1450 should improve the communication since the idle 30mV is no longer in the indetermined/undefined region. 

    Best,
    Andrew 

  • 0 in reply to Andrew J
    Prodigy 190 points

    Hello Andrew-san,

    Thank you for your reply.

    The customer has also asked the following additional questions:

    Currently, the transmission distance is 1.2km, and the baud rate is 1200/2400/4800 (standard)/9600bps.
    I would appreciate it if you could let me know if the "ISO1450DW" is suitable, or if there are any other models you would recommend.

    Best regards,

  • 0 in reply to Okutsu
    TI__Mastermind 22345 points

    Hello Okutsu,

    Yes, ISO1450DW would be suitable for the cable length of 1.2km at 9600 BAUD and lower data rates. 

    The RS-485 Design Guide (Rev. D)

    Best,
    Andrew