AAT1151IKS-1.0-T1 View Datasheet(PDF) - Advanced Analogic Technologies
Part Name
Description
MFG CO.
'AAT1151IKS-1.0-T1' PDF : 16 Pages View PDF
AAT1151
850kHz 700mA Synchronous
Buck DC/DC Converter
Design Example
Specifications
IOUT
IRIPPLE
VOUT
VIN
FS
TAMB
0.7A
40% of Full Load at Max VIN
1.5V
2.7V to 4.2V (3.6V nominal)
850kHz
85°C
Maximum Input Capacitor Ripple
IRMS= IO ·
VO · ⎛1-
VIN ⎝
VO ⎞
VIN ⎠
= 0.35Arms,
VIN
=
2
·
VO
P = esr · IRMS2 = 5mΩ · 0.352 A = 0.6mW
Inductor Selection
L=
VOUT
IO ⋅ k ⋅ FS
⋅ ⎛⎝1
-
VOUT⎞
VIN ⎠
=
0.7A
⋅
1.5V
0.4 ⋅
850kHz
⋅ ⎛⎝1 -
1.5V ⎞
4.2V⎠
=
4.05μH
Select Sumida inductor CDRH3D16 3.3μH 63mΩ 1.8mm height.
ΔI =
L
VO
⋅ FS
⋅
⎛⎝1
-
VO ⎞
VIN⎠
=
1.5V
3.3μH ⋅ 850kHz
⋅
⎛⎝1-
1.5V⎞
4.2V⎠
=
340mA
IPK
=
IOUT
+
ΔI
2
=
0.7A
+
0.17A
=
0.87A
P = IO2 ⋅ DCR = (0.7)2 ⋅ 63mΩ = 31mW
Output Capacitor Ripple Current
IRMS =
1
2·
·
3
VOUT · (VIN - VOUT)
L · FS · VIN
= 1 · 1.5V · (4.2V - 1.5V) = 99mArms
2· 3 3.3μH · 850kHz · 4.2V
Pesr = esr · IRMS2 = 5mΩ · 992 mA = 50μW
1151.2007.01.1.6
13
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