The high side supply voltage for the gate driver
and as well for the are monitored by an additional boot strap UVLO comparator. This
comparator monitors the differential voltage between SWx and HBx. This protection
supports the two modes in the following manner.
- If the measured voltage
drops below VTH-(BST_UV) in fPWM mode the converter stops
operation after a trimmed amount of switching cycles.
- In PSM i.e. 2 switching phase
buck-boost operation, the BOOT_UV triggers switching of the converter to
re-fresh the boot strap voltage. If the initiated switching does not bring
up the BOOT_UV after the trimmed amount of re-fresh cycles the fPWM
protection deactivates the converter operation.