Datasheet

Dynamic Switching of the MOSFETs
UCC27200 , UCC27201
SLUS746B – DECEMBER 2006 – REVISED NOVEMBER 2008 ....................................................................................................................................... www.ti.com
The true behavior of MOSFETS presents a dynamic capacitive load primarily at the gate to source threshold
voltage. Using the turn off case as the example, when the gate to source threshold voltage is reached the drain
voltage starts rising, the drain to gate parasitic capacitance couples charge into the gate resulting in the turn off
plateau. The relatively low threshold voltages of many MOSFETS and the increased charge that has to be
removed (Miller charge) makes good driver performance necessary for efficient switching. An open loop half
bridge power converter was utilized to evaluate performance in actual applications. The schematic of the
half-bridge converter is shown in Figure 30 . The turn off waveforms of the UCC27200 driving two MOSFETs in
parallel is shown in Figure 28 and Figure 29 .
Figure 28. V
LO
Fall Time in Half-Bridge Converter Figure 29. V
HO
Fall Time in Half-Bridge Converter
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