BMTL is the effective burst mode
threshold (entering and exiting) from system level. BMTL and FBreplica are the
inputs for the pick higher block.
Internally, for digital state machine, BMTL is the burst mode entering threshold
and BMTH is the burst mode exiting threshold. When Vcomp is between BMTL and
BMTH, the switching pulses are continuous.
ZCS protection disabled when Fbreplica is lower than BMTH. So BMTH can be
adjusted to prevent nuisance ZCS protection.