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xtr117 is not working, power supply is 12VDC serial with a 510 ohm resisitor, but Vreg is 1.2 V respect to Iret.

Bin Sun
Intellectual 360 points
Other Parts Discussed in Thread: XTR117

As I said in the title. The regulator is not working. When I link the circuit as showed in picture and turned the resistor, the Io is not changing.

Does Anyone know why?

  • 0
    TI__Guru 63225 points
    Hi Bin,

    This sounds like a compliance voltage issue where the supply voltage is not high enough to support the load resistor and output current. We wrote a blog about this subject which you can read here: e2e.ti.com/.../two-wire-4-20-ma-transmitters-background-and-common-issues

    Try reducing the load resistor to 0 or 10Ohms or increase the supply current to >20V and see if the output current reacts as expected.
  • 0 in reply to Collin Wells
    Intellectual 360 points
    Thanks. Learned a lot in the blog. But when I used 1 ohm as load resistor before, the Io is 20 mA minimum. Do you have any idea about this?
  • 0 in reply to Collin Wells
    Intellectual 360 points

    I changed the load resistor to 200. The power is 12V. The Io is 40 mA without input cause I removed the Vreg, and the Vreg was 2.3 V. Everything is not right.

    Please help me out of here.

  • 0 in reply to Bin Sun
    TI__Guru 63225 points

    Hi Bin,

    Try using the attached SPICE simulation file to debug and understand your system better.  The model uses some ideal components so it should be used to check basic understanding and operating functions of the XTR117 product.  If you notice very large voltages or currents, then it's likely something is not connected properly.

    I suggest you double-check all of your circuit connections because the circuit should provide basic functionality as you've drawn it. This is shown in the SPICE simulations below:

    XTR117_Potentiometer.TSC