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AAT2550 Datasheet, PDF (33/35 Pages) Advanced Analogic Technologies – Total Power Solution for Portable Applications | |||
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AAT2550
Total Power Solution for Portable Applications
2.5V Output Capacitor
COUT
=
3 · ÎILOAD
VDROOP · FS
=
3 · 0.3A
0.2V · 1.4MHz
= 3.2μF
IRMS(MAX)
=
1
2·
3
·
(VOUT) · (VIN(MAX) - VOUT)
L · FS · VIN(MAX)
=
1 · 2.5V · (4.2V - 2.5V)
2· 3 10μH · 1.4MHz · 4.2V
= 21mArms
Pesr = esr · IRMS2 = 5mΩ · (21mA)2 = 2.2μW
1.8V Output Capacitor
COUT
=
3 · ÎILOAD
VDROOP · FS
=
3 · 0.3A
0.2V · 1.4MHz
= 3.2μF
IRMS(MAX)
=
1
2·
3
·
(VOUT) · (VIN(MAX) - VOUT)
L · FS · VIN(MAX)
=
1 · 1.8V · (4.2V - 1.8V) = 45mArms
2· 3 4.7μH · 1.4MHz · 4.2V
Pesr = esr · IRMS2 = 5mΩ · (45mA)2 = 10μW
Input Capacitor
Input Ripple VPP = 25mV.
CIN =
â VPP
â IO1 + IO2
1
-
ESRâ
â
·
4
·
FS
=
â 25mV
â 0.8A
1
= 6.8μF
- 5mΩââ · 4 · 1.4MHz
I = RMS(MAX)
IO1 + IO2
2
= 0.4Arms
P = esr · IRMS2 = 5mΩ · (0.4A)2 = 0.8mW
2550.2006.07.1.0
33
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