VIN: This input is a conventional, noninverting, high-impedance input of the internal operational amplifier (OPA). The internal circuitry is protected by clamp diodes to supplies. An additional clamp connected to approximately 18V protects internal circuitry. Place a small resistor in series with the input to limit the current into the protection if voltage can be present without the XTR111 being powered. Consider a resistor value equal to R_SET for bias current cancellation.

SET: The total resistance connected between this pin and VIN reference sets the transconductance. Additional series resistance can degrade accuracy and drift. The voltage on this pin must not exceed 14V because this pin is not protected to voltages greater than this level.

IS: This output pin is connected to the transistor source of the external FET. The accuracy of the output current to IS is achieved by dynamic error correction in the current mirror. Keep this pin within 6.5V the positive supply. An internal clamp is provided to protect the circuit; however, the internal clamp must be externally current-limited to less than 50mA.

VG: The gate drive for the external FET is protected against shorts to the supply and GND. The circuit is clamped to stay within 18V of the positive supply. Protect the external FET if the FET gate has the potential to exceed specified ratings.

REGF: The output of the regulator buffer can source up to 5mA of current, but has very limited sinking capability; less than 50μA. The maximum short-circuit current is in the range of 15mA to 25mA, changing over temperature.

REGS: This pin is the sense input of the voltage regulator and is referenced to an internal 3V reference circuit. The input bias current can be up to 2μA. Avoid capacitive loading of REGS that can compromise the loop stability of the voltage regulator.

VSP: The supply voltage of up to a maximum of 44V allows operation in harsh industrial environment and provides headroom for easy protection against overvoltage. Use a large enough bypass capacitor (> 100nF) and eventually a damping inductor or a small resistor (5Ω) to decouple the XTR111 supply from the noise typically found on the 24V supplies.

EF: The active‑low error flag (logic output) is intended for use with an external pullup resistor to logic-high for reliable operation when this output is used. However, this pin has a weak internal pullup resistor to 5V; leave unconnected if not used.

OD: This control input has a 4μA internal pullup resistor disabling the output. A pulldown resistor or short to GND is required to activate the output. Control OD to reduce output glitches during power on and power off. This logic input controls the output. If not used, connect this pin to GND. The regulator is not affected by OD.