The adjustable output voltage device variant of LM62440-Q1 is externally adjustable using a resistor divider network. The range of recommended output voltage is found in Section 8.3. The divider network is comprised of R_FBT and R_FBB, and closes the loop between the output voltage and the converter. The converter regulates the output voltage by holding the voltage on the FB pin equal to the internal reference voltage, V_REF. The resistance of the divider is a compromise between excessive noise pickup and excessive loading of the output. Smaller values of resistance reduce noise sensitivity but also reduce the light load efficiency. The recommended value for R_FBT is 100 kΩ with a maximum value of 1 MΩ. If 1 MΩ is selected for R_FBT, then a feedforward capacitor must be used across this resistor to provide adequate loop phase margin (see Section 10.2.2.10). Once R_FBT is selected, Equation 2 is used to select R_FBB. V_REF is nominally 1 V. For this 5-V example, R_FBT = 100 kΩ and R_FBB = 24.9 kΩ are chosen.

For the fixed output voltage versions, FB is connected directly to the output voltage node, preferably, near the top of the output capacitor. If the feedback point is located further away from the output capacitors (that is, remote sensing), then a small 100-nF capacitor can be needed at the sensing point.