SNVSBW1C December 2021 – August 2024 LM63440-Q1 , LM63460-Q1
PRODUCTION DATA
The gate driver of the high-side (HS) switch requires a bias voltage higher than VIN. The bootstrap capacitor, CBOOT, connected between CBOOT and SW, works as a charge pump to boost the voltage on CBOOT to a level of VCC above the SW voltage. The LM634x0-Q1 has an integrated bootstrap diode to minimize external component count. Use a 100nF bootstrap capacitor rated for 10V or higher. The VBOOT-UVLO threshold (2.1V typical) is designed to maintain proper HS switch operation. If the bootstrap capacitor voltage drops below VBOOT-UVLO, then the converter initiates a charging sequence, turning on the low-side switch before attempting to turn on the HS switch.