bd91361muv ROHM Co. Ltd., bd91361muv Datasheet - Page 9

• Manufacturer Part Number: bd91361muv
• Description: Single-chip Type With Built-in Fet Switching Regulators
• Manufacturer: ROHM Co. Ltd.

●Switching regulator efficiency
BD91361MUV
© 2010 ROHM Co., Ltd. All rights reserved.
www.rohm.com
Efficiency ŋ may be expressed by the equation shown below:
η=
Efficiency may be improved by reducing the switching regulator power dissipation factors P
Dissipation factors:
1) ON resistance dissipation of inductor and FET : PD(I
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(I
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)=
4)PD(ESR)=I
5)PD(IC)=Vin×I
ON resistance of FET, I
V
OUT
2
Vin×Iin
R)=I
×I
OUT
Vin
OUT
RMS
2
2
×(R
CC
×C
2
×ESR (I
×100[%]=
RSS
I
COIL
(I
DRIVE
CC
×I
+R
[A] : Circuit current.)
OUT
OUT
ON
RMS
[A] : Output current.)
) (R
P
×f
Pin
OUT
[A] : Ripple current of capacitor, ESR[Ω] : Equivalent series resistance.)
COIL
×100[%]=
(C
[Ω] : DC resistance of inductor, R
RSS
[F]:Reverse transfer capacitance of FET, I
P
OUT
P
2
OUT
R)
+P
9/17
D
α
×100[%]
ON
[Ω] :
DRIVE
D
[A]:Peak current of gate.)
α as follows:
Technical Note
2010.06 - Rev.A