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DAC161P997: Suggestion to use 4 DAC161P997 in a single system with Common 24V Loop+

Karan Thawani
Prodigy 50 points
Part Number: DAC161P997
Other Parts Discussed in Thread: XTR117, DAC8775, DAC80504

7024.DocScanner 10-Sep-2022 9-44 am.pdf

Hello Everyone.

A very good morning.

We are planning to use 4 DAC161P997 in a single board to provide accurate 4-20mA output. We will be happy to hear your inputs regarding whether we require 4 separate +24V Loop+ supply or we can use the single one. I have attached  proposed block diagram.

Can we use this kind of configuration to control 4 separate current control loops with Loop+ Shared among them. Please advise for the same,

  • 0
    Prodigy 50 points

    Hello TI team,

    Our design is on hold due to this point. Please advise us on this so we can continue our design.

    Regards,

    Karan Thawani

  • 0 in reply to Karan Thawani
    TI__Guru 53283 points

    The DAC161P997 is design to be a remote transmitter on a 4-20mA bus.  In your figure, it seems like you are trying to make it the current output of a controller.  That could potentially work, but keep in mind that this device creates its own ground reference relative to VLOOP+ and VLOOP-.   You have multiple loads which means that he local "VLOOP-" for each DAC might be a different voltage as compared to common VLOOP+.  So it really depends on how your are configuring your system.  Are you planning to use a common controller for all 4 DACs? You would probably need isolators on each DAC because their GROUND values would all be different. 

    If you are trying to design a system where you have a controller that produces 4 unique current outputs that can be used on different loads, then consider a DAC8775 or maybe a DAC80504 with a separate XTR device, like the XTR117.

    Thanks,

    Paul

  • 0 in reply to Paul_Frost
    Prodigy 50 points

    Yes, We are planning to use common Micro Controller(MCU). There will be OPTO Isolators between Each DAC's DIN channel and MCU. So Input side of each OPTO will be controlled by 4 different GPIOs of our MCU and they will share the MCU ground. But, Output side of each OPTO will go to to their respected separate DAC DIN with respect to each DAC's own ground (They will not be shared means COMA,COMD of all DACs will not be connected)