BD8963EFJ-E2(2010) データシートの表示（PDF） - ROHM Semiconductor

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BD8963EFJ-E2
(Rev.:2010)

Low Noise High-efficiency Switching Regulator with Built-in Power MOSFET

ROHM Semiconductor 

BD8963EFJ

Technical Note

●Switching regulator efficiency

Efficiency ŋ may be expressed by the equation shown below:

η= VOUT×IOUT ×100[%]= POUT ×100[%]=

Vin×Iin

Pin

POUT

×100[%]

POUT+PDα

Efficiency may be improved by reducing the switching regulator power dissipation factors PDα as follows:

Dissipation factors:

1) ON resistance dissipation of inductor and FET：PD(I2R)

2) Gate charge/discharge dissipation：PD(Gate)

3) Switching dissipation：PD(SW)

4) ESR dissipation of capacitor：PD(ESR)

5) Operating current dissipation of IC：PD(IC)

1)PD(I2R)=IOUT2×(RCOIL+RON) (RCOIL[Ω]：DC resistance of inductor, RON[Ω]：ON resistance of FET, IOUT[A]：Output

current.)

2)PD(Gate)=Cgs×f×V (Cgs[F]：Gate capacitance of FET, f[H]：Switching frequency, V[V]：Gate driving voltage of FET)

3)PD(SW)= Vin2×CRSS×IOUT×f

IDRIVE

(CRSS[F]：Reverse transfer capacitance of FET, IDRIVE[A]：Peak current of gate.)

4)PD(ESR)=IRMS2×ESR (IRMS[A]：Ripple current of capacitor, ESR[Ω]：Equivalent series resistance.)

5)PD(IC)=Vin×ICC (ICC[A]：Circuit current.)

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2010.06 - Rev.A

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