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How to use DAC7760 as loop powered 4-20mA transmitter

pochkumar malyala
Prodigy 160 points
Other Parts Discussed in Thread: DAC7760, XTR117, DAC161S997, XTR115, XTR116

I have successfully interface 2 DAC7760 to micro controller through SPI and observed output is performing good.

I want to use this DAC4-20mA output as loop powered 4-20mA output.

To measure DAC output signal we need to connect Operating Voltage, Ground and Out signal.

Where as in Loop Powered 4-20mA transmitter Operating Voltage and Output Signal enough.

Is any possibility to meet this requirement, if there is a chance please share me application details.

And I also want know about the performance of both DAC7760 4-20 mA output and Loop Powered 4-20 mA transmitter.

Let me know which best mechanism for industrial (pharma) applications, either DAC7760 4-20 mA output or Loop Powered 4-20 mA transmitter.

Awaiting for your valuable response.

Thanks & Regards,

Poch

  • 0
    TI__Genius 10615 points

    Hello Poch,

    Apologies with the delay of this response. I thought I had already answered a previous thread. Maybe the forum post didn't go through like I intended.

    Loop powered 4-20 mA transmitters are analogous to “2-wire transmitters” (ie. loop+ and loop-). The DAC7760 is not designed to be used in 2-wire transmitters but in 3-wire transmitters (Supply, Out, Gnd) and 4-wire (Supply, Gnd1, Out, Gnd2). One of the critical requirements for the design of a 4-20 mA 2-wire transmitter is that the components must consume < 4 mA of current. In current mode, the DAC7760 already exceeds this with AIDD + DIDD ≥4 mA.

     

    If you are interested in designing a 2-wire loop transmitter, I recommend that you take a look at TIPD158. The document focuses on the design of a low-cost isolated 2-wire transmitter. You can use this as a guide for your design and interchange parts to fit your requirements.

    If you want more information on 2-wire vs 3 wire DACs take a look at this blog about Industrial analog outputs and architectures.

    I would also suggest an industrial DAC series.

    Regarding some alternative devices for there architectures you could take a look at XTR115, XTR116, XTR117, and the DAC161S997.

    pochkumar malyala said:
    Let me know which best mechanism for industrial (pharma) applications, either DAC7760 4-20 mA output or Loop Powered 4-20 mA transmitter.

    All architectures are very common in the space. Generally, the difference lies, in if the sensor requires more than 4 mA, you mus use 3-wire or 4-wire.

    If you can share some of the details of what you hope to accomplish with this design. Maybe I can suggest alternatives.