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| AAT1110_06 Datasheet, PDF (17/19 Pages) Advanced Analogic Technologies – Fast Transient 800mA Step-Down Converter | |||
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AAT1110
Fast Transient 800mA Step-Down Converter
Input Capacitor
Input Ripple VPP = 25mV
1
CIN =
â
â
VPP
IO
- ESRââ · 4 · FS
=
â 25mV
â 0.6A
1
= 4.87μF; use 4.7μF
- 5mΩââ · 4 · 1.4MHz
IRMS =
IO
2
= 0.3Arms
P = esr · IRMS2 = 5mΩ · (0.3A)2 = 0.45mW
AAT1110 Losses
PTOTAL
=
IO2
·
(RDSON(HS)
·
VO
+ RDSON(LS)
VIN
·
[VIN
-VO])
+ (tsw · F · IO + IQ) · VIN
0.62 · (0.725Ω · 1.8V + 0.7Ω · [4.2V - 1.8V])
=
4.2V
+ (5ns · 1.4MHz · 0.4A + 70μA) · 4.2V = 268mW
TJ(MAX) = TAMB + ÎJA · PLOSS = 70°C + (160°C/W) · 268mW = 113°C
1110.2006.04.1.0
17
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