AS1324
Data Sheet - Application Information
The total losses of the coil have a strong impact on the efficiency of the dc/dc conversion and consist of both the losses
in the dc resistance and the following frequency-dependent components:
1. The losses in the core material (magnetic hysteresis loss, especially at high switching frequencies)
2. Additional losses in the conductor from the skin effect (current displacement at high frequencies)
3. Magnetic field losses of the neighboring windings (proximity effect)
4. Radiation losses
Table 5. Recommended Inductors
Part Number
L
DCR
97mΩ
150mΩ
175mΩ
110mΩ
35mΩ
50mΩ
72mΩ
105mΩ
Current Rating Dimensions (L/W/T)
Manufacturer
Murata
www.murata.com
LQH32CN2R2M33
LQH32CN4R7M33
LPS3008-222MLC
LPS3015-222MLC
MOS6020-222MLC
MOS6020-472MLC
CDRH3D16NP-2R2N
CDRH3D16ND-4R7N
2.2µH
4.7µH
2.2µH
2.2µH
2.2µH
4.7µH
2.2µH
4.7µH
790mA
650mA
3.2x2.5x2.0mm
3.2x2.5x2.0mm
3.1x3.1x0.8mm
3.1x3.1x1.5mm
6.0x6.8x2.4mm
6.0x6.8x2.4mm
4.0x4.0x1.8mm
4.0x4.0x1.8mm
Coilcraft
www.coilcraft.com
1100mA
2000mA
3260mA
1820mA
1200mA
900mA
Sumida
www.sumida.com
Figure 26. Efficiency Comparison of Different Inductors, VIN = 2.7V, VOUT = 1.8V and 1.2V
95
90
85
80
75
70
95
90
85
80
75
70
VOUT = 1.8V
VOUT = 1.2V
LQH32CN2R2
LPS3015-222
LQH32CN4R7
LPS3008-222
M OS6020-222
M OS6020-472
LQH32CN2R2
LPS3015-222
LQH32CN4R7
LPS3008-222
M OS6020-222
M OS6020-472
1
10
100
1000
1
10
100
1000
Output Current (mA)
Output Current (mA)
Output Capacitor Selection
The advanced fast-response voltage mode control scheme of the AS1324 allows the use of tiny ceramic capacitors.
Because of their lowest output voltage ripple low ESR ceramic capacitors are recommended. X7R or X5R dielectric
output capacitor are recommended.
At high load currents, the device operates in PWM mode and the RMS ripple current is calculated as:
VOUT
--------------
1 –
(EQ 4)
VIN
----------------------- ----------------
1
IRMSC
= VOUT
×
×
OUT
L × f
2 ×
3
While operating in PWM mode the overall output voltage ripple is the sum of the voltage spike caused by the output
capacitor ESR plus the voltage ripple caused by charging and discharging the output capacitor:
VOUT
--------------
1 –
(EQ 5)
VIN
-----------------------
1
⎛
⎝
⎞
--------------------------------
ΔVOUT = VOUT
×
×
+ ESR
⎠
L × f
8 × COUT × f
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Revision 1.03
12 - 20
AMSCO [ AMS(艾迈斯) ]
