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| AAT1123 Datasheet, PDF (16/20 Pages) Advanced Analogic Technologies – 1MHz Step-Down Converter | |||
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AAT1123
1MHz Step-Down Converter
Input Capacitor
Input Ripple VPP = 25mV
1
1
CIN =
â
â
VPP
IO
- ESRââ · 4 · FS
=
â 25mV
â 0.4A
- 5mΩââ · 4 · 1MHz
= 4.75µF
IRMS =
IO
2
= 0.2Arms
P = esr · IRMS2 = 5mΩ · (0.2A)2 = 0.2mW
AAT1123 Losses
PTOTAL
=
IO2
·
(RDSON(HS)
·
VO
+ RDSON(LS)
VIN
·
[VIN
-VO])
+ (tsw · F · IO + IQ) · VIN
0.42 · (0.725Ω · 1.8V + 0.7Ω · [4.2V - 1.8V])
=
4.2V
+ (5ns · 1.0MHz · 0.4A + 50μA) · 4.2V = 122mW
TJ(MAX) = TAMB + ÎJA · PLOSS = 85°C + (160°C/W) · 122mW = 104.5°C
16
1123.2006.05.1.5
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