A voltage divider between output voltage and the FB pin is used to adjust output voltage. See Figure 8-1.
The LM6x4xx-Q1 uses a 1-V reference for control to derive Equation 1. This equation can be used to determine RFBB for a desired output voltage and a given RFBT. Usually, RFBT is limited to a maximum value of 100 kΩ to prevent shifting due to PCB leakage under harsh conditions. A larger resistance of up to 1 MΩ can be used to improve light load efficiency in cleaner environments, or the fixed output voltage options under harsher conditions.
In addition, a feedforward capacitor CFF can be used to optimize the transient response.