ZHCSKA2A September 2019 – February 2020 LMR36520
PRODUCTION DATA.
The output voltage of LMR36520 is externally adjustable using a resistor divider network. The range of recommended output voltage is found in the Recommended Operating Conditions. 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 100 kΩ with a maximum value of 1 MΩ. If a 1 MΩ is selected for RFBT, then a feedforward capacitor must be used across this resistor to provide adequate loop phase margin (see the CFF Selection section). Once RFBT is selected, use Equation 3 to select RFBB. VREF is nominally 1 V.
For this 5-V example, values are: RFBT = 100 kΩ and RFBB = 24.9 kΩ.