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4-20 mA Isolation

Siva Nageswara Bandreddy
Prodigy 10 points

Other Parts Discussed in Thread: ISO1212, ISO1211, ISO7741, ISO7742

Hi,

In our circuit we are using HART protocol(4 to 20mA), which is generated by DAC ,this 4 to 20mA output directly connected to external system.

 Now we need to isolated 4 to 20mA from DAC output to external system.

Can you please suggest the isolator part number.

Thanks in advance

Regards,

siva

  • 0
    TI__Genius 17100 points

    Hi Siva,

    Thank you for posting to E2E! Our ISO1212 or ISO1211 devices can be used to isolate 4-20mA analog signals and achieve a digital output.*

    Can you please share details of the signal to isolate (analog input, corresponding output?) and a block diagram of this system? In the meantime, please do expect a follow up response from TI during normal business hours M - F.


    Thank you,
    Manuel Chavez

    *Post was updated to remove suggestion of using ISO121x devices for isolating HART signals directly

  • 0 in reply to Manuel Chavez
    TI__Genius 17100 points

    Hi Silva,

    I apologize, but ISO121x is not suited for HART applications as it accepts analog inputs and outputs only binary digital signals. I will correct my previous post. However, isolating digital signals over analog signals preserves signal integrity, so a simple and reliable solution with TI isolation is to use a digital isolator in between the DAC and MCU, FPGA, or PLC it is communicating with.

    An example of this topology is shown below, with the isolation blocks (using TI's ISO7741 and ISO7742 devices) highlighted. Instead of isolating HART signals, the isolation barrier is placed in the UART/SPI communication paths:



    Is this helpful for your project? The block diagram above is from TI-Design 060020, and TI does recommend the ISO774x devices for general digital isolation.


    Thank you for your time, and welcome to E2E!

    Manuel Chavez