ZHCSPC5 October 2022 LM51231-Q1
PRODUCTION DATA
Boost converters have a natural pass-through path from the supply to the load through the high-side MOSFET body diode when the supply voltage is greater than the target load voltage. During this operating condition, the high-side MOSFET dissipates power due to the forward voltage drop of the body diode. To reduce the power dissipation the high-side MOSFET (HO) is driven at 100% duty cycle and VLOAD is approximately equal to VSUPPLY. This mode of operation is called bypass mode.
The device behaves differently in bypass mode based on the selected light load switching mode operation, the sensed inductor current, and the input voltage. To enter bypass mode; the OVP status must be triggered for at least 30 μs (VOVTH-DLY), see Section 7.3.8 and the voltage between CSP and CSN must be greater than 6 mV (VCS-FWD). To exit bypass mode either the OVP status is cleared, or VSW-SENSE is less than bypass mode zero cross threshold. The bypass mode zero cross threshold is dependent on the selected light-load switching mode operation and detailed in Section 7.4.1.4.1 and Section 7.4.1.4.2, for DE mode and FPWM respectively.