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  • TI Thinks Resolved

XTR115: Loop Current Changes with Loop voltage

Part Number: XTR115

Hello,

I am using XTR115 in my application and the circuit works fine (except some non linearity) with 4 to 20mA output. when I changed Vloop from 16V to 24V, the DC loop current jumped to 30mA from 4mA. 

The other question I have is, if Rload always required or we can just measure current using a meter connected in sereies with Vloop.

Thanks.

  • Hi Naresh,

    It sounds like there may be an issue with your connection or schematic as 30mA is close to the short circuit output current of the XTR115. There is no reason that increasing the supply voltage would force the output into the short circuit current limit so there may be an issue on the input or you might be making a connection between the loop supply ground and IRET. If you can share more details and ideally a schematic I can assist you further.

    Rload is not required, so long as you have a closed loop. Using a meter as Rload should work just fine.

    Regards,

    Zak Kaye
    Precision Amplifiers Applications 

  • In reply to Zak Kaye:

    Zak,

    Thank you for your reply. Please find my schematic below, it shows only relevant portion. It gets signal from a sensor.

    If XTR115's output ever gets above 30mA, does it permanently damage the chip?

    Thanks.

  • In reply to Naresh Patel2:

    Hi Naresh,

    I apologize for the delayed response on this, have you been able to resolve this issue?

    I don't see anything wrong with the schematic. Please be sure that the ground used for IRET is not shared on the output side. If for example you are measuring the output with one of the leads of your probe connected to the same ground as IRET, then the current loop will be broken. The input sensor will also need to be referenced to IRET, and shouldn't provide any path to the supply ground.

    Is there anything else that has changed other than the supply value? Was the board re-soldered at any point?

    With regards to the current, the XTR115 internally limits the current to a maximum of 32mA. This can be adjusted as described in the datasheet, but if you force current in excess of 45mA through the device then you may begin to damage the part.

    Regards,

    Zak Kaye
    Precision Amplifiers Applications 

  • In reply to Zak Kaye:

    Hello Zak,

    I had resoldered a potentiometer at one point and added a load resistor to get Voltage output. I will put together a new board and see if the issue is resolved. Other than that, everything looks fine.

    Thank you for your support.

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