SLUSEI6 November 2021 UCC28781-Q1
PRODUCTION DATA
As VCST drops to VCST(MIN), UCC28781-Q1 enters into SBP1 mode and PWMH continues to stay disabled. The purpose of SBP1 is to lower fBUR in order to minimize power loss. SBP1 fixes NSW at two and VCST to VCST(MIN), while the burst off-time is adjusted to regulate the output voltage. As fBUR is well below fLPM, the switching-related loss can be minimized. In addition, lowering fBUR forces both the isolated gate driver and controller to remain in wait states longer to minimize the static power loss. The equivalent static current of the controller in SBP can be represented as