The output voltage is set by an external resistor divider (R1, R2 in Figure 8-1). When the output voltage is regulated, the typical voltage at the FB pin is V_REF. Thus the resistor divider is determined by Equation 4.

Equation 4.

where

• V_OUT is the regulated output voltage
• V_REF is the internal reference voltage at the FB pin

For best accuracy, keep R2 smaller than 300 kΩ to ensure the current flowing through R2 is at least 100 times larger than the FB pin leakage current. Changing R2 towards a lower value increases the immunity against noise injection. Changing the R2 towards a higher value reduces the quiescent current for achieving highest efficiency at low load currents.