bd9153muv ROHM Co. Ltd., bd9153muv Datasheet - Page 12

• Manufacturer Part Number: bd9153muv
• Description: Output 1.5a Or Less High Efficiency Step-down Switching Regulator With Built-in Power Mosfet
• Manufacturer: ROHM Co. Ltd.

●Selection of components externally connected
© 2009 ROHM Co., Ltd. All rights reserved.
BD9153MUV
www.rohm.com
I
1. Selection of inductor (L)
L
2. Selection of output capacitor (C
※Current exceeding the current rating of the inductor results in magnetic saturation of the inductor, which decreases efficiency.
If V
※Select the inductor of low resistance component (such as DCR and ACR) to minimize dissipation in the inductor for
Fig.35 Output ripple current
Fig.36 Output capacitor
The inductor must be selected allowing sufficient margin with which the peak current may not exceed its current rating.
better efficiency.
CC
=5.0V, V
V
CC
V
L
CC
L=
IL
L
OUT
V
(5-1.2)×1.2
0.45×5×1.0M
OUT
=1.2V, f=1.0MHz, ΔI
ΔI
Co
L
ESR
Co
V
OUT
O
)
=2.02μ → 2.2[μH]
Output capacitor should be selected with the consideration on the stability region
and the equivalent series resistance required to smooth ripple voltage.
Output ripple voltage is determined by the equation (4)：
ΔV
(ΔI
※Rating of the capacitor should be determined allowing sufficient margin against
L
=0.3×1.5A=0.45A, for example,(BD9153MUV)
output voltage. A 22µF to 100μF ceramic capacitor is recommended.
Less ESR allows reduction in output ripple voltage.
OUT
L
: Output ripple current, ESR: Equivalent series resistance of output capacitor)
=ΔI
L
×ESR [V]・・・(4)
The inductance significantly depends on output ripple current.
As seen in the equation (1), the ripple current decreases as the
inductor and/or switching frequency increases.
Appropriate ripple current at output should be 20% more or less of
the maximum output current.
12/18
ΔI
ΔI
(ΔI
L
L
L=
L
=
=0.2×I
: Output ripple current, and f: Switching frequency)
(V
(V
CC
CC
OUT
L×V
ΔI
-V
-V
OUT
max. [A]・・・(2)
OUT
L
×V
CC
)×V
)×V
×f
CC
×f
OUT
OUT
[A]・・・(1)
[H]・・・(3)
Technical Note
2009.08 - Rev.A