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DAC161S997: Multi Channel 2wire current Loop

Fabian Hladik
Prodigy 70 points

Part Number: DAC161S997

Dear TI Support Team,

we are currently develloping a new sensor-product featuring 3 analog outputs and would kindly ask for your assistance (with component selection)

Requirements for analog outputs:
 -  2-Wire current loops (Shared positive supply)
 -  Output current: 4-20mA
 -  Accuracy: < 10µA
 -  Resolution: <=2µA
 - Temperature depencende: <2µA/°C

The product must be supplied by one (or possibly all three current loops).

Since GND is at "LOOP-" of every output chanel (and the potential of LOOP- varies with output current), digital isulation is neccecairy. 

Please see the attatched concept-drawing.

1) Is the DAC161S997 suitable for this usecase / alternative suggestions

2) Do you have any practical experience with this multi-channel concept, or any suggestions?

Thanks a lot in advance

grafik.png

  • 0
    TI__Expert 5570 points

    Hi Fabian,

    In my understanding, when trying to have multiple loops regulated in a two wire setup, each DAC116S997 will need its own loop supply. If not, you will have each DAC trying to regulate the loop current from the shared supply, causing errors in the current value. The 24V from the PLC is a shared power supply in your diagram, correct?

    If using a 3-wire configuration where the analog signal current is separate from the power supply loop, you can have a single shared power supply for multiple current output loops.
    Industrial DACs: An overview of analog outputs and architectures 

    Thank you,
    Lucas