bd8301muv ROHM Co. Ltd., bd8301muv Datasheet - Page 8

• Manufacturer Part Number: bd8301muv
• Description: High-efficiency Step-up/down Switching Regulators With Built-in Power Mosfet
• Manufacturer: ROHM Co. Ltd.

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BD8301MUV
c
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Reference Application Data
(1) Output inductor
2009 ROHM Co., Ltd. All rights reserved.
100
90
80
70
60
50
40
30
20
10
0
⊿IL=
⊿IL=
⊿IL=
1
Fig.19 Power conversion efficiency
* Current over the coil rating flowing in the coil brings the coil into magnetic saturation, which may lead to lower
efficiency or output oscillation. Select an inductor with an adequate margin so that the peak current does not exceed
the rated current of the coil.
VBAT=2.8V
(η: Efficiency, ∆IL: Output ripple current, f: Switching frequency)
As a guide, output ripple current should be set at about 20 to 50% of the maximum output current.
Ipeak =Iout ×(Vout/VIN) /η+ ∆IL/2 [A]
A shielded inductor that satisfies the current rating (current value, Ipeak as shown in the drawing below) and has a
low DCR (direct current resistance component) is recommended.
Inductor values affect output ripple current greatly.
Ripple current can be reduced as the coil L value becomes larger and the
switching frequency becomes higher as the equations shown below.
(Vin-Vout)
|(Vin-Vout)|
(Vout-Vin)
OUTPUT CURRENT [mA]
10
VBAT=4.2V
L
L
L
VBAT=3.7V
×
×
100
×
Vout
Vout
Vin
Vin
Vout×2×0.85
(Vin+Vout)
1000
×
×
1
1
f
f
[A] (in step-down mode)
[A] (in step-up mode)
3.33
3.32
3.31
3.30
3.29
3.28
3.27
×
2.0
1
f
Io=600mA
Fig.20 Line regulation
[A] (in step-up/down mode)
3.0
INPUT VOLTAGE [V]
8/13
4.0
(1)
5.0
(4)
6.0
(2)
3.33
3.32
3.31
3.30
3.29
3.28
3.27
Fig. 22 Ripple current
1
(3)
VBAT=3.7V
Fig.21 Load regulation
OUTPUT CURRENT [mA]
10
Technical Note
2009.05 - Rev.B
Δ I
L
100
1000