I am designing a sensor with a 4-20mA output and I plan to use the XTR115. I know the the XTR115 has an internal 5V regulator, but my sensor circuitry requires at least 7V. If I connect a load between the V+ pin and IRET pins, will the XTR115 still operate correctly? If so, I can connect the VIN pin of an external 7V regulator to V+ and the GND pin of the regulator to IRET and create the 7V that I need.
Yes, the circuit you describe will operate properly. If you return all the current drawn from the V+ terminal to the Iret pin, it will be accurately included in the output current of the transmitter. This must include the ground current of the 7V regulator and its load current.
The total current drawn from V+ by your circuitry (including any current drawn from Vreg and Vref) cannot exceed 3.7mA. Exceeding this 3.7mA total current would prevent the output current from achieving its 4mA output current at low scale input.
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