XTR115: Loop Current Changes with Loop voltage

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.

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.

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.