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Application Note
BD71837MWV Platform Design Guide
© 2018 ROHM Co., Ltd.
No. 61AN002E Rev.001
May.2018
5.3. BUCK Convertors
In this section, application circuits for each voltage rail are explained.
For more detail information, the document of “BD71837MWV schematic check list” can be referred to.
5.3.1. BUCK1 (VDD_SoC)
BUCK1 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. BUCK1 output voltage range is from 0.7V to 1.3V
by 10mV step.
5.3.1.1. Schematic Example
Figure 5.7 BUCK1 Schematic Example
5.3.1.2. Schematic checklist
Table 5.2 BUCK1 schematic checklist
Pin Names
Dir.
Notes (Unit of parts size : mm)
Check
Buck1 (VDD_SoC)
BUCK1_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
BUCK1_LX[1:0]
O
Connect to BUCK1 via the inductor.
Connect
one
0.47μH
±20% inductors to BUCK1_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
BUCK1_FB
I
Connect to the sense pin of BUCK1_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.
