AAT1120IES-0.6-T1 View Datasheet(PDF) - Advanced Analogic Technologies
Part Name
Description
MFG CO.
'AAT1120IES-0.6-T1' PDF : 20 Pages View PDF
AAT1120
500mA Step-Down Converter
Step-Down Converter Design Example
Specifications
VO = 1.8V @ 250mA, Pulsed Load ΔILOAD = 200mA
VIN = 2.7V to 4.2V (3.6V nominal)
FS
= 1.5MHz
TAMB = 85°C
1.8V Output Inductor
µsec
µsec
L1 = 1.67 A ⋅ VO2 = 1.67 A ⋅ 1.8V = 3µH (use 3.0μH; see Table 1)
For Sumida inductor CDRH2D09-3R0, 3.0μH, DCR = 150mΩ.
ΔIL1 =
VO
L1 ⋅ FS
⋅
⎛⎝1
-
VO ⎞
VIN⎠
=
1.8V
3.0µH ⋅ 1.5MHz
⋅
⎛⎝1 -
1.8V ⎞
4.2V ⎠
= 228mA
IPKL1
=
IO
+
ΔIL1
2
=
250mA
+
114mA
=
364mA
PL1 = IO2 ⋅ DCR = 250mA2 ⋅ 150mΩ = 9.375mW
1.8V Output Capacitor
VDROOP = 0.1V
COUT
=
3 · ΔILOAD
VDROOP · FS
=
3 · 0.2A
0.1V · 1.5MHz
= 4µF (use 4.7µF)
IRMS
=
1 · (VO) · (VIN(MAX) - VO) = 1 ·
2· 3
L1 · FS · VIN(MAX) 2· 3
1.8V · (4.2V - 1.8V) = 66mArms
3.0µH · 1.5MHz · 4.2V
Pesr = esr · IRMS2 = 5mΩ · (66mA)2 = 21.8µW
1120.2007.01.1.0
15
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