AAT1149IJS-0.6-T1 View Datasheet(PDF) - Analog Technology Inc
Part Name
Description
MFG CO.
'AAT1149IJS-0.6-T1' PDF : 20 Pages View PDF
AAT1149
3MHz Fast Transient
400mA Step-Down Converter
Step-Down Converter Design Example
Specifications
VO = 1.8V @ 400mA (adjustable using 0.6V version), Pulsed Load ΔILOAD = 300mA
VIN = 2.7V to 4.2V (3.6V nominal)
FS
= 3.0MHz
TAMB = 85°C
1.8V Output Inductor
μsec
μsec
L1 = 1 A ⋅ VO = 1 A ⋅ 1.8V = 1.8μH (use 2.2μH; see Table 1)
For Taiyo Yuden inductor CBC2518T2R2M, 2.2μH, DCR = 130mΩ.
ΔIL1 =
VO
L1 ⋅ FS
⋅
⎛⎝1
-
VO ⎞
VIN ⎠
=
1.8V
2.2μH ⋅ 3.0MHz
⋅
⎛
⎝1 -
1.8V⎞
4.2V⎠
= 156mA
IPKL1
=
IO
+
ΔIL1
2
=
0.4A
+
0.078A
=
0.478A
PL1 = IO2 ⋅ DCR = 0.4A2 ⋅ 130mΩ = 21mW
1.8V Output Capacitor
VDROOP = 0.1V
COUT
=
3 · ΔILOAD
VDROOP · FS
=
3 · 0.3A
0.1V · 3.0MHz
= 3.0μF; use 4.7µF
IRMS
=
1 · (VO) · (VIN(MAX) - VO) = 1 ·
2· 3 L1 · FS · VIN(MAX)
2· 3
1.8V · (4.2V - 1.8V) = 45mArms
2.2μH · 3.0MHz · 4.2V
Pesr = esr · IRMS2 = 5mΩ · (45mA)2 = 10μW
16
1149.2006.11.1.0
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