The driver of the power switch (HS switch) requires bias higher than VIN when the HS switch is ON. The capacitor connected between CBOOT and SW works as a charge pump to boost voltage on the BOOT pin to (VSW + VCC). The boot diode is integrated on the LM76002/LM76003 die to minimize physical size. TI recommends a 0.47-µF, 6.3-V or higher capacitor for CBOOT. The VBOOT_UVLO threshold is typically 2.2 V. If the CBOOT capacitor is not charged above this voltage with respect to SW, the device initiates a charging sequence using the low-side FET.