In synchronous rectification using Nch MOSFETs on both the high side and the low side, why is it that operation at a 100% duty cycle is not possible as with a high-side Pch MOSFET, and that the maximum duty cycle is limited?|FAQ|ROHM Semiconductor

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In synchronous rectification using Nch MOSFETs on both the high side and the low side, why is it that operation at a 100% duty cycle is not possible as with a high-side Pch MOSFET, and that the maximum duty cycle is limited?
- In order to drive a high-side Nch MOSFET, the gate voltage must be higher than the drain voltage. For this reason a bootstrap circuit is provided, but in order to charge the chargeup capacitor with electric charge, the low-side MOSFET must be turned on and the switching pin must be low. Because this requires some time, there is a limit to the maximum duty cycle.