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AAT2550 Datasheet, PDF (32/35 Pages) Advanced Analogic Technologies – Total Power Solution for Portable Applications | |||
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AAT2550
Total Power Solution for Portable Applications
Step-Down Converter Design Example
Specifications
VO1 = 2.5V @ 400mA (adjustable using 0.6V version), pulsed load ÎILOAD = 300mA
VO2 = 1.8V @ 400mA (adjustable using 0.6V version), pulsed load ÎILOAD = 300mA
VIN = 2.7V to 4.2V (3.6V nominal)
FS = 1.4MHz
TAMB = 85°C
2.5V VO1 Output Inductor
L1
=
3
μsec
A
â
VO1
=
3
μsec
A
â
2.5V = 7.5μH
(see Table 5)
For Sumida inductor CDRH3D16, 6.8µH, DCR = 170mΩ.
ÎI1 =
VO
L1 â
FS
â
ââ1
-
VO1â
VINâ
=
2.5V
6.8μH â
1.4MHz
â
ââ1
-
2.5Vâ
4.2Vâ
=
106mA
IPK1
=
IO1
+
ÎI1
2
=
0.4A
+
0.053A
=
0.453A
PL1 = IO12 â
DCR = 0.452 â
170mΩ = 0.452A2 â
170mΩ = 34mW
1.8V VO2 Output Inductor
L2
=
3
μsec
A
â
VO2
=
3
μsec
A
â
1.8V = 5.4μH
(see Table 5)
For Sumida inductor CDRH3D16, 4.7µH, DCR = 105mΩ.
ÎI2 =
VO2
L â
FS
â
â1
â
-
VO2â
VIN â
=
1.8V
4.7μH â
1.4MHz
â
ââ1
-
1.8V â
4.2Vâ
= 156mA
IPK2
=
IO2
+
ÎI2
2
=
0.4A
+
0.078A
=
0.48A
PL2 = IO22 â
DCR = 0.4A2 â
105mΩ = 17mW
32
2550.2006.07.1.0
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