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Application Note
BD71837MWV Platform Design Guide
© 2018 ROHM Co., Ltd.
No. 61AN002E Rev.001
May.2018
5.3.2.2. Schematic checklist
Table 5.3 BUCK2 schematic checklist
Pin Names
Dir.
Notes (Unit of parts size : mm)
Check
BUCK2 (VDD_ARM)
BUCK2_VIN[1:0]
I
Connect to the 5V power supply in the system.
As a decoupling capacitor, use
one 10μF
.
Select the input capacitor with the capacitance
≧
3.5μF
including the DC bias effect
at VSYS=5.0V.
<The recommended part of capacitor is shown below.>
A.LMK107BBJ106MALT, size:1608, capacitance: 10μF, tolerance:10V
BUCK2_LX[1:0]
O
Connect to BUCK2 via the inductor.
Connect
one
0.47μH
±20% inductors to BUCK2_LX0 and 1.
Select the inductor to be used according to board area and cost restrictions.
<The recommended part of inductor is shown below.>
A.HMLE32251E-R47MSR, size: 3225 , Rated DC Current : 7.2A
As output capacitors, use
two
22μF
capacitors.
Select the output capacitors within the capacitance range defined in the datasheet
of BD71837MWV.
<The recommended part of 22μF capacitor is shown below.>
A.GRM188R60J226MEA0D, size:1608, capacitance: 22μF, tolerance:6.3V
BUCK2_FB
I
Connect to the sense pin of BUCK2_FB to near output capacitors.
Note: Some dummy pads for output capacitors should be prepared like the reference schematic for the fine tuning in the actual board.
5.3.2.3. Layout Example
About the parts placement for each capacitor around BUCK2, the below reference layout can be referred to.
BUCK2_FB should be connected to near output capacitors.
Figure 5.10 BUCK2 Layout Example (Top Layer)
Output Cap
BUCK2_VIN
BUCK2_LX
Input Cap
Feedback
point
Inductor
