AAT1157IVN-T1 View Datasheet(PDF) - Analog Technology Inc
Part Name
Description
MFG CO.
'AAT1157IVN-T1' PDF : 14 Pages View PDF
Design Example
Specifications
IOUT 1.2A
IRIPPLE 330mA
VOUT 2.5V
VIN 3.0V to 4.2V
FS
1MHz
TAMB = 85°C
Maximum Input Capacitor Ripple:
IRMS = IO ·
VO · ⎛1- VO ⎞ = 0.59Arms
VIN ⎝ VIN ⎠
P = esr · IRMS2 = 5mΩ · 0.592 A = 1.7mW
AAT1157
1MHz 1.2A Buck DC/DC Converter
Inductor Selection:
L
=
VOUT
∆IPP ⋅ F
⋅
⎛⎝1
-
VOUT⎞
VIN ⎠
=
2.5V
0.33A ⋅ 1MHz
⋅
⎛⎝1 -
2.5V⎞
4.2V⎠
= 3.07µH
Select Sumida inductor CDRH5D28 3.0µH.
∆I =
VO
L⋅F
⋅
⎛⎝1
-
VO
VIN
⎞
⎠
=
2.5V
3.0µH ⋅ 1MHz
⋅ ⎛⎝1-
2.5V⎞
4.2V⎠
= 340mA
IPK
=
IOUT
+
∆I
2
=
1.2A
+
0.17A
=
1.37A
P = IO2 ⋅ DCR = (1.2A)2 ⋅ 31mΩ = 45mW
Output Capacitor Ripple Current:
IRMS =
1
2·
·
3
(VOUT) · (VIN - VOUT)
L · F · VIN
=
1·
2· 3
2.5V · (4.2V - 2.5V)
3.0µH · 1MHz · 4.2V
= 97.4mArms
Pesr = esr · IRMS2 = 5mΩ · (97.4mA)2 = 47.4µW
1157.2005.11.1.4
11
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