SNVSCJ0A November 2023 – February 2024 LMR38025-Q1
PRODUCTION DATA
In an adjustable output voltage version, pin 5 of the device is FB. The output voltage of the LMR38025-Q1 is externally adjustable using an external resistor divider network. The divider network is comprised of RFBT and RFBB 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, VREF. 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 RFBT is 100kΩ with a maximum value of 1MΩ. After RFBT is selected, Equation 9 is used to select RFBB. VREF is nominally 1V.
For this 5V example, RFBT = 100kΩ and RFBB = 24.9kΩ is chosen.