The current output stage consists of a preconditioner and a current source as conceptualized in Figure 8-3. This stage provides a current output according to the DAC code. The output range can be programmed as 0 mA to
20 mA, 0 mA to 24 mA, or 4 mA to 20 mA. An external boost transistor can be used to reduce the power dissipation of the device. The maximum compliance voltage on pin IOUT equals (AVDD – 2 V). In single power-supply mode, the maximum AVDD is 36 V, and the maximum compliance voltage is 34 V. After power on, the IOUT pin is in a Hi-Z state.

Figure 8-3 Current Output

Resistor R_SET (used to convert the DAC voltage to current) determines the stability of the output current over temperature. If desired, an external, low-drift, precision 15-kΩ resistor can be connected to the ISET-R pin and used instead of the internal R_SET resistor.

For a 5-V reference, the output can be expressed as shown in Equation 3 through Equation 5.

For a 0-mA to 20-mA output range:

Equation 3.

For a 0-mA to 24-mA output range:

Equation 4.

For a 4-mA to 20-mA output range:

Equation 5.

where

• CODE is the decimal equivalent of the code loaded to the DAC.
• N is the bits of resolution; 16 for DAC8760 and 12 for DAC7760.

The current-output range is normally set according to the value of the RANGE bits in the Control Register. When both the voltage and current outputs are enabled in dual-output mode, the range is set by the IOUT RANGE bits in the Configuration Register. See Section 8.4.1 for more details. For more details on controlling the current output when both the VOUT and IOUT pins are simultaneously enabled, see Section 9.1.1.