Datasheet
UCC27323, UCC27324, UCC27325
UCC37323, UCC37324, UCC37325
SLUS492H –JUNE 2001–REVISED MAY 2013
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The switching load presented by a power MOSFET converts to an equivalent capacitance by examining the gate
charge required to switch the device. This gate charge includes the effects of the input capacitance plus the
added charge needed to swing the drain of the device between the ON and OFF states. Most manufacturers
provide specifications that provide the typical and maximum gate charge, in nC, to switch the device under
specified conditions. Using the gate charge Qg, determine the power that must be dissipated when charging a
capacitor which is done by using the equivalence Qg = CeffV to provide Equation 6 for power:
P = C × V
2
× f = Qg × f (6)
Equation 6 allows a power designer to calculate the bias power required to drive a specific MOSFET gate at a
specific bias voltage.
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