The value of resistors R2 and R3 establish the undervoltage lockout level as shown in Figure 26. Include a small level of capacitance (approximately 0.1 µF) at the UVLO pin for noise immunity. If the application does not require drop-out operation (operation when VIN approximates VLED) program a UVLO level allows no switching to occur until there is adequate input voltage available.
Select the desired amount of voltage hysteresis and the desired turn-ON threshold (VIN-RISE_THRESHOLD). Because of the small amount of fixed-voltage hysteresis and fixed-hysteresis current, some combinations of turn-ON and turn-OFF thresholds are not possible. If the calculation results in values that are zero or negative, the combinations selected are not possible. After selecting a turn-ON point and desired amount of voltage hysteresis (VHYST) use Equation 13 and Equation 14 to calculate R3 and R2.