AAT1123IJS View Datasheet(PDF) - Skyworks Solutions
Part Name
Description
MFG CO.
'AAT1123IJS' PDF : 18 Pages View PDF
DATA SHEET
AAT1123
1MHz Step-Down Converter
Step-Down Converter Design Example
Specifications
VO = 1.8V @ 400mA (adjustable using 0.6V version), Pulsed Load ILOAD = 300mA
VIN = 2.7V to 4.2V (3.6V nominal)
FS = 1.0MHz
TAMB = 85°C
1.8V Output Inductor
L1
=
3
μsec
A
μsec
⋅ VO2 = 3 A
⋅ 1.8V = 5.4μH
(see
Table
1)
For Sumida inductor CDRH3D16, 4.7μH, DCR = 105m.
ΔIL1 =
VO
L1 ⋅ F
⋅
⎛⎝1
-
VO ⎞
VIN ⎠
=
1.8V
4.7μH ⋅ 1.0MHz
⋅
1
-
⎛
⎝
1.8V⎞
4.2V⎠
=
218mA
IPKL1
=
IO
+
ΔIL1
2
=
0.4A
+
0.11A
=
0.51A
PL1 = IO2 ⋅ DCR = 0.4A2 ⋅ 105mΩ = 17mW
1.8V Output Capacitor
VDROOP = 0.05V
COUT
=
3 · ΔILOAD
VDROOP · FS
=
3 · 0.3A
0.05V · 1MHz
= 18.0μF
IRMS
=
1 · (VO) · (VIN(MAX) - VO) = 1
2· 3
L1 · F · VIN(MAX)
2·
·
3
1.8V · (4.2V - 1.8V) = 63mArms
4.7μH · 1.0MHz · 4.2V
Pesr = esr · IRMS2 = 5mΩ · (63mA)2 = 20μW
Input Capacitor
Input Ripple VPP = 25mV
1
1
CIN = ⎛ VPP
⎝ IO
- ESR⎞⎠ · 4 · FS
=
⎛ 25mV
⎝ 0.4A
- 5mΩ⎞⎠ · 4 · 1MHz
= 4.75µF
IRMS =
IO
2
= 0.2Arms
P = esr · IRMS2 = 5mΩ · (0.2A)2 = 0.2mW
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
14
201975B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 15, 2013
Share Link: 
