BD9D321EFJ Datasheet, PDF (15/28 Pages) Rohm – 4.5V to 18V Input, 3.0A Integrated MOSFET 1ch Synchronous Buck DC/DC Converter

BD9D321EFJ
Application Example
Datasheet
Figure 28. Application Circuit
VOUT [V]
1.0
1.05
1.2
1.8
3.3
5.0
7.0
Table 1. Recommended Component values
R1 [kΩ]
R2 [kΩ]
C1 [pF]
6.8
22
- ^{(Note 6)}
8.2
22
- ^{(Note 6)}
12+0.51
22
- ^{(Note 6)}
30
22
- ^{(Note 6)}
68+5.1
22
- ^{(Note 6)}
120+1.8
22
- ^{(Note 6)}
180
22
- ^{(Note 6)}
L [µH] ^{(Note 7)}
1.5
1.5
1.5
2.2
2.2
3.3
3.3
(Note 6) C1 is a feed forward capacitor. The IC can operate normally even if the capacitor is not connected.
Additional phase boost can be achieved by adding the 5pF to 100pF capacitor (C1) in parallel with R1.
(Note 7) Recommended Inductor ・ALPS GLMC series
・TDK SPM6530 series
Selection of Components Externally Connected
(1) Output LC Filter Constant
The DC/DC converter requires an LC filter for smoothing the output voltage in order to supply a continuous current to the
load. Selecting an inductor with a large inductance causes the ripple current ∆I_L that flows into the inductor to be small.
However, decreasing the ripple voltage generated in the output is not advantageous in terms of the load transient
response characteristic. An inductor with a small inductance improves the transient response characteristic but causes the
inductor ripple current to be large which increases the ripple voltage in the output voltage, showing a trade-off relationship.
The recommended inductor values are shown in Table 1.
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TSZ22111•15•001
15/25
TSZ02201-0J3J0AC00490-1-2
07.Aug.2013 Rev.001