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© 2019 ROHM Co., Ltd.
No. 62AN124E Rev.001
Dec.2019
Application Note
Power Management IC designed for “NXP® i.MX 8M Mini”
BD71847AMWV 1x22µF Buck Output Capacitor
1. Introduction
This documen t su mmari zes t he BD71847AMWV electr ica l perfor mance w hile reducing the BUCK output cap acitor s from 2pcs x 22µF
to 1pcs.
2. Conclusion
If the BUCK regulators of BD71847AMW V operate in forced PWM mode, the capacitance can be reduced to 1x 22µF each buck in
order to optimize the BOM cost and furthermore reduce the PCB area. The following charac teristics have been confirmed to ensure
that the SoC specifications are met.
- Transient Response
- AC-Ripple Voltage
However, if high efficiency in light load system is r equested, it is recommended to use 2x 22µF and run the BUCKs in Aut o mode.
Power Rail Name
for i.MX 8M Mini Platform
BD71847AMWV VR
Recommended ext ernal
parts
With Forced PWM mode
Recommended ext ernal
parts
With A uto Mode
VDD_ARM
BUCK2
0.9V / 3.0A with DVS
L=0.47uH, Cout=22µF x 1 L=0.47uH, Cout=22µF x
2
VDD_SOC
BUCK1
0.8V / 3.0A with DVS
L=0.47uH, Cout=22µF x 1 L=0.47uH, Cout=22µF x
2
VDD_VPU/GPU/DRAM
BUCK5
1.0V / 3.0A with DVS
L=0.47uH, Cout=22µF x 1 L=0.47uH, Cout=22µF x
2
NVCC_3V3
BUCK6
3.3V / 3.0A
L=1uH, Cout=22µF x 1 L=1uH, Cout=22µF x
2
NVCC_DRAM
BUCK8
1.1V / 3.0A
L=0.47uH, Cout=22µF x
1 L=0.47uH, Cout=22µF x
2
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Application Note
BD71847AMWV 1x22µF Buck Output Capacitor
© 2019 ROHM Co., Ltd.
No. 62AN124E Rev.001
Dec.2019
3. Validation Results (1 x 22μF output capacitor)
3.1 Transient Response summary (1 x 22μF output capacitor)
Ta = -40˚C, 25˚C, 105˚C
VSYS = 3.8V
VR
Typ.
Voltage
[V]
Load
Current
[mA]
Transient Response Results
Worst Case Results
Droop Limit
[mV]
Droop
[mV]
Overshoot
Limit
[mV]
Overshoot
[mV]
BUCK1
0.8
0 to 3000
45
32
350
31
BUCK2
0.9
0 to 3000
45
32
250
33
BUCK5
0.9
0 to 3000
45
34
250
31
BUCK6*
3.3
0 to 3000
300
130
500
118
BUCK7
1.8
0 to 1500
150
42
350
39
BUCK8
1.1
0 to 3000
40
34
40
30
3.2 AC-Ripple summary (1 x 22μF buck output capacitor)
Ta = -40˚C, 25˚C, 105˚C
VSYS = 3.8V
VR Typ.
Load
Current
[mA]
Maximum Ripple Voltage
Worst Case Result
Limit [mV]
AC-Ripple
[mV]
DC-set-point
[mV]
WC [mV]
BUCK1
0.8
0 / 3000
45
+/-9
12.8 / 13.2
15.6
BUCK2
0.9
0 / 3000
45
+/-10
11.6 / 12.4
16.2
BUCK5
0.9
0 / 3000
45
+/-10
10.4 / 11.6
15.8
BUCK6*
3.3
0 / 3000
300
+/-33
12.0 / 12.0
39
BUCK7
1.8
0 / 1500
150
+/-18
12.0 / 12.0
24
BUCK8
1.1
0 / 3000
40
+/-11
14.0 / 13.6
18
4 Revision History
Date
Revision
Number
Description
13
th
.Dec.2019 001 First Release