JAJSE40A October 2017 – February 2018 UCC28780
PRODUCTION DATA.
As VCST drops to VCST(MIN), UCC28780 enters into SBP mode and PWMH continues to stay disabled. The purpose of SBP is to lower fBUR in order to minimize standby power. SBP 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 gate driver and UCC28780 to remain in wait states longer to minimize the static power loss. The equivalent static current of the UCC28780 in SBP can be represented as