ZHCSO70A march 2023 – may 2023 LMR36501 , LMR36502
PRODUCTION DATA
If other voltages are desired, VOUT / FB can be connected to a feedback resistor divider network to set the output voltage. 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 VOUT / FB pin equal to the internal reference voltage, VREF. The converter determines whether fixed output voltage or adjustable output voltage is required by sensing the resistance of the feedback path during start-up. To ensure that the converter regulates to the desired output voltage, the typical minimum value for the parallel combination of RFBT and RFBB is 5 kΩ while the typical maximum value is 10 kΩ as shown in Equation 6. Equation 7 can be used as a starting point to determine the value of RFBT. Reference Table 9-4 for a list of acceptable resistor values for various output voltages.
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 maximum value for RFBT is 200 kΩ. For a 3.3-V example, LMR36502F3RPE
output pin
(VOUT / FB) can connect directly to the
output capacitor.
| VOUT (V) | RFBT (1) (kΩ) | RFBB (1) (kΩ) |
|---|---|---|
| 1.2 | 10.2 | 51.1 |
| 2.5 | 24.9 | 16.5 |
| 3.3 | 33.2 | 14.3 |
| 5 | 49.9 | 12.4 |
| 12 | 110 | 10 |
| 24 | 200 | 8.66 |