R19AN0047EJ0100
Rev.1.00
Aug. 10, 2017
RAA457100GBM
Selection of the Inductor for DCDC Converter
R19AN0047EJ0100 Rev.1.00
Aug. 10, 2017
Page 1 of 4
APPLICATION NOTE
Table
1. External component values of the RAA457100 DCDC converter
Setting voltage of SYS C
VCC
[uF] C
BAT
[uF] L
DD
[uH] C
DD
[uF] C
SGND
[uF] R
DD
[Ω]
1.2V ,1.5V ,1.8V 4.7 1.0 10 3.3 0.47 0
3.0V 4.7 1.0 10 4.7 1.0 0.33
*
There is a possibility to change the value for improving the performance.
Figure1. The circuit of DCDC converter of the RAA457100
When the inductor current exceeds a rated current, the inductor may cause magnetic saturation. Magnetic saturation will cause the
efficiency decreases and the destruction of IC. Please choose the inductor so that a peak current does not exceed the rated current in
the range of use.
The circuit of DCDC converter of the RAA457100 is shown in Figure1. External component values of DCDC converter are shown in the
Table 1, and Inductor list is shown Table 2.
Table
2. Inductor list
Part Number Manufacturer
Inductance
[uH]
DCR (typ)
[Ω]
Isat (typ)
[mA]
Size [mm]
L(typ) W(typ) T(max)
VLS252008ET-100M-CA
TDK
Corporation
10 1.026 480 2.5 2.0 0.80
VLS252010CX-100M 10 0.483 750 2.5 2.0 1.0
VLS201610CX-100M 10 0.610 620 2.0 1.6 1.0
LQH2HPN100MGR
Murata
Manufacturing
Co., Ltd.
10 0.560 700 2.5 2.0 1.0
LQH2HPN100MDR 10 1.200 420 2.5 2.0 0.60
LQH2MPN100MGR 10 0.880 610 2.0 1.6 0.95
*
DCR: Series resistance
Isat :Saturation current
Table 2 is an example and does not limit inductors. Please consider according to the conditions for use.
Please refer to the inductor maker for the details.
L
DD
C
DD
Step-Down
DCDC Converter
SYS
LX
DFET
R
DD
C
SGND
VCC
C
VCC
RAA457100GBM User system
Power supply
GND
BAT
C
BAT
V
BAT
GND
SGND
VCC
RAA457100GBM Selecting Inductor for DCDC Converter
R19AN0047EJ0100 Rev.1.00
Aug. 10, 2017
Page 2 of 4
Typical performance characteristics of DCDC converter (for reference)
Typical performance characteristics of DCDC converter are shown blow. These values are reference data, and are not guaranteed.
Evaluate the DCDC converter enough, and then select inductor.
Efficiency vs. Output current (V
BAT
=3.8V)
Output Voltage vs. Output current (V
BAT
=3.8V)
40
50
60
70
80
90
100
0.1 1 10 100
Efficiency [%]
Output Current [mA]
VLS252008ET-100M VLS252010CX-100M VLS201610CX-100M
LQH2HPN100MGR LQH2HPN100MDR LQH2MPN100MGR
SYS=1.2V
40
50
60
70
80
90
100
0.1 1 10 100
Efficiency [%]
Output Current [mA]
VLS252008ET-100M VLS252010CX-100M VLS201610CX-100M
LQH2HPN100MGR LQH2HPN100MDR LQH2MPN100MGR
40
50
60
70
80
90
100
0.1 1 10 100
Efficiency [%]
Output Current [mA]
VLS252008ET-100M VLS252010CX-100M VLS201610CX-100M
LQH2HPN100MGR LQH2HPN100MDR LQH2MPN100MGR
40
50
60
70
80
90
100
0.1 1 10 100
Efficiency [%]
Output Current [mA]
VLS252008ET-100M VLS252010CX-100M VLS201610CX-100M
LQH2HPN100MGR LQH2HPN100MDR LQH2MPN100MGR
SYS=1.5V
SYS=1.8V
SYS=3.0V
1.10
1.15
1.20
1.25
1.30
0.1 1 10 100
SYS Voltage [V]
Output Current [mA]
VLS252008ET-100M VLS252010CX-100M VLS201610CX-100M
LQH2HPN100MGR LQH2HPN100MDR LQH2MPN100MGR
1.40
1.45
1.50
1.55
1.60
0.1 1 10 100
SYS Voltage [V]
Output Current [mA]
VLS252008ET-100M VLS252010CX-100M VLS201610CX-100M
LQH2HPN100MGR LQH2HPN100MDR LQH2MPN100MGR
SYS=1.2V
SYS=1.5V
1.70
1.75
1.80
1.85
1.90
0.1 1 10 100
SYS Voltage [V]
Output Current [mA]
VLS252008ET-100M VLS252010CX-100M VLS201610CX-100M
LQH2HPN100MGR LQH2HPN100MDR LQH2MPN100MGR
2.90
2.95
3.00
3.05
3.10
0.1 1 10 100
SYS Voltage [V]
Output Current [mA]
VLS252008ET-100M VLS252010CX-100M VLS201610CX-100M
LQH2HPN100MGR LQH2HPN100MDR LQH2MPN100MGR
SYS=1.8V
SYS=3.0V