A precision 1.0-V reference voltage (V_REF) is used to maintain a tightly regulated output voltage over the entire operating temperature range. The output voltage is set by a resistor divider from the output voltage to the FB pin. TI recommends to use 1% tolerance resistors with a low temperature coefficient for the FB divider. Select the bottom-side resistor R_FBB for the desired divider current and use Equation 1 to calculate the top-side resistor R_FBT. TI recommends R_FBT in the range from 10 kΩ to 100 kΩ for most applications. A lower R_FBT value can be used if static loading is desired to reduce V_OUT offset in PFM operation. Lower R_FBT reduces efficiency at very light load. Less static current goes through a larger R_FBT and can be more desirable when light-load efficiency is critical. TI does not recommend R_FBT larger than 1 MΩ because it makes the feedback path more susceptible to noise. Larger R_FBT values require more carefully designed feedback path on the PCB. The tolerance and temperature variation of the resistor dividers affect the output voltage regulation.

Figure 8-2 Output Voltage Setting