29/46
Application Note
BD71837MWV Platform Design Guide
© 2018 ROHM Co., Ltd.
No. 61AN002E Rev.001
May.2018
5.3.4. BUCK4 (VDD_VPU)
BUCK4 is a high-efficiency buck converter which converts VSYS (2.7V to 5.5V) voltage to a regulated voltage. This VR can
dynamically change its output voltage setting using the I2C interface. BUCK4 output voltage range is from 0.7V to 1.3V by 10mV
step.
5.3.4.1. Schematic Example
Figure 5.13 BUCK4 Schematic Example
5.3.4.2. Schematic Checklist
Table 5.5 BUCK4 schematic checklist
Pin Names
Dir.
Notes (Unit of parts size : mm)
Check
BUCK4 (VDD_VPU)
BUCK4_VIN
I
Connect to the 5V power supply in the system.
As a decoupling capacitor, use
one 4.7μF
.
Select the input capacitor with the capacitance
≧
1.88μF
including the DC bias
effect at VSYS=5.0V.
<The recommended part of capacitor is shown below.>
A.LMK107BJ475MA, size:1608, capacitance: 4.7μF, tolerance:10V
BUCK4_LX
O
Connect to BUCK3 via the inductor.
Connect
one
0.47μH
±20% inductors to BUCK3_LX.
Select the inductor to be used according to board area and cost restrictions.
<The recommended part of inductor is shown below.>
A.MAMK2520HR47M, size: 2520 , Rated DC Current : 5.8A
As output capacitors, use
one
22μF
capacitor.
Select the output capacitors within the capacitance range defined in the datasheet
of BD71837MWV.
<The recommended part of 22μF capacitor is shown below.>
A.GRM188R60J22
6MEA0D, size:1608, capacitance: 22μF, tolerance:6.3V
BUCK4_FB
I
Connect to the sense pin of BUCK4_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.
