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When selecting an N-FET, three important parametersare the total gate charge (Qg), on-resistance (rDS(ON)),and reverse transfer capacitance (CRSS).Qg takes into account all capacitances associated withcharging the gate. Use the typical Qg value for bestresults; the maximum value is usually grossly overspecifiedsince it is a guaranteed limit and not the measuredvalue. The typical total gate charge should be50nC or less. With larger numbers, the EXT pins maynot be able to adequately drive the gate. The EXTrise/fall time varies with different capacitive loads asshown in the Typical Operating Characteristics.The two most significant losses contributing to theN-FET’s power dissipation are I2R losses and switchinglosses. Select a transistor with low rDS(ON) and lowCRSS to minimize these losses.