Each of the two high-side MOSFET drivers is
biased from its floating bootstrap capacitor, which is normally re-charged by VCC
through both the external and internal bootstrap diodes when the low-side MOSFET is turned on.
When the TPS552882 operates exclusively in the buck or boost regions, one of the high-side
MOSFETs is constantly on. An internal charge path, from VOUT and BOOT2 to BOOT1 or from VIN
and BOOT1 to BOOT2, charges the bootstrap capacitor to VCC so that the high-side
MOSFET remains on.