The high-side switch driver circuit requires a bias voltage higher than VIN to ensure the HS switch is turned ON. The capacitor connected between BOOT and SW works as a charge pump to boost voltage on the BOOT terminal to (SW+VCC). The boot diode is integrated on the LMR436x0-Q1 die to minimize physical solution size. A 100-nF capacitor rated for 10 V or higher is recommended for CBOOT. The BOOT rail has a UVLO setting. This UVLO has a threshold of VBOOT-UVLO and is typically set at 2.1 V. If the CBOOT capacitor is not charged above this voltage with respect to the SW pin, then the part initiates a charging sequence, turning on the low-side switch before attempting to turn on the high-side device.