AS1324 Ver la hoja de datos (PDF) - austriamicrosystems AG
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AS1324 Datasheet PDF : 20 Pages
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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
LQH32CN2R2M33
LQH32CN4R7M33
LPS3008-222MLC
LPS3015-222MLC
MOS6020-222MLC
MOS6020-472MLC
CDRH3D16NP-2R2N
CDRH3D16ND-4R7N
L
2.2µH
4.7µH
2.2µH
2.2µH
2.2µH
4.7µH
2.2µH
4.7µH
DCR
97mΩ
150mΩ
175mΩ
110mΩ
35mΩ
50mΩ
72mΩ
105mΩ
Current Rating Dimensions (L/W/T)
Manufacturer
790mA
650mA
3.2x2.5x2.0mm
3.2x2.5x2.0mm
Murata
www.murata.com
1100mA
2000mA
3.1x3.1x0.8mm
3.1x3.1x1.5mm
Coilcraft
www.coilcraft.com
3260mA
6.0x6.8x2.4mm
1820mA
6.0x6.8x2.4mm
1200mA
900mA
4.0x4.0x1.8mm
4.0x4.0x1.8mm
Sumida
www.sumida.com
Figure 26. Efficiency Comparison of Different Inductors, VIN = 2.7V, VOUT = 1.8V and 1.2V
95
VOUT = 1.8V
95
VOUT = 1.2V
90
90
85
85
80
80
75
70
1
LQH3 2 CN2 R2
LPS3 0 15- 2 2 2
LQH3 2 CN4 R7
LPS3 0 0 8 - 2 2 2
M OS6020-222
M OS6020-472
10
100
Output Current (mA)
1000
75
70
1
LQH3 2 CN2 R2
LPS3 0 15- 2 2 2
LQH3 2 CN4 R7
LPS3 0 0 8 - 2 2 2
M OS6020-222
M OS6020-472
10
100
Output Current (mA)
1000
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:
IRMSCOUT
=
VOUT
×
1-----–--L----V---×--V---O-----fI---U-N------T---
×
-------1---------
2× 3
(EQ 4)
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:
ΔVOUT
=
VOUT
×
1-----–-----V------V---O-----I---U-N------T---
L×f
×
⎛
⎝
---------------1-----------------
8 × COUT × f
+
E
SR⎠⎞
(EQ 5)
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Revision 1.03
12 - 20
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