The TPS715 family contains an adjustable version, the TPS71501, which sets the output voltage using an external resistor divider as shown in Figure 8-2. The output voltage operating range is 1.205 V to 15 V, and is calculated using:

Equation 2.

where:

• V_REF = 1.205 V (typical)

Choose resistors R1 and R2 allows approximately 1.5 μA of current through the resistor divider. Lower value resistors can be used for improved noise performance, but consume more power. Avoid higher resistor values because leakage current into or out of FB across R1 / R2 creates an offset voltage that is proportional to V_OUT divided by V_REF. The recommended design procedure is to choose R2 = 1 MΩ to set the divider current at 1.5 μA, and then calculate R1 using Equation 3:

Figure 8-2 depicts this configuration.