SNVSBY6 October 2021 LM61430-Q1
The driver of the high-side (HS) switch requires bias higher than VIN. The capacitor, CBOOT, connected between CBOOT and SW works as a charge pump to boost voltage on the CBOOT pin to SW+VCC. A boot diode is integrated on the LM61430-Q1 die to minimize external component count. It is recommended that a 100-nF capacitor rated for 10-V or higher is used. The VBOOT_UVLO threshold (2.1-V typical) is designed to maintain proper HS switch operation. If the CBOOT capacitor voltage drops below VBOOT_UVLO, then the device initiates a charging sequence turning on the low-side switch before attempting to turn on the HS switch.