AAT2554
Total Power Solution for Portable Applications
Input Capacitor
Input Ripple VPP = 25mV
1
1
CIN =
=
= 1.38µF (use 4.7µF)
⎛
⎝
VPP
IO
⎞
⎠
⎛
⎝
25mV
0.2A
⎞
- ESR
·
4
·
FS
- 5mΩ
· 4 · 1.5MHz
⎠
IO
IRMS
=
= 0.1Arms
2
P = esr
·
IRMS2 = 5mΩ
·
(0.1A)2 = 0.05mW
AAT2554 Losses
IO2 · (RDSON(H) · VO + RDSON(L) · [VIN -VO
]
)
PTOTAL
=
VIN
+ (tsw · FS · IO + IQ) · VIN
0.22 · (0.59
Ω
·
1.8V + 0.42Ω
4.2V
· [4.2V - 1.8V])
=
+ (5ns · 1.5MHz · 0.2A + 30µA) · 4.2V = 26.14mW
TJ(MAX) = TAMB + ΘJA · PLOSS = 85°C + (50°C/W) · 26.14mW = 86.3°C
2554.2007.01.1.2
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