APS1056 View Datasheet(PDF) - Advanced Analogic Technologies
Part Name
Description
MFG CO.
'APS1056' PDF : 20 Pages View PDF
APS1056
Fast Transient 600mA Step-Down Converter
Step-Down Converter Design Example
Specifications
VO = 1.8V @ 600mA (adjustable using 0.6V version), Pulsed Load ∆ILOAD = 300mA
VIN = 2.7V to 4.2V (3.6V nominal)
FS
= 1.4MHz
TAMB = 85°C
1.8V Output Inductor
µsec
L1 = 3 A
⋅
VO2
=
3
µsec
A
⋅ 1.8V = 5.4µH
(use 4.7µH; see Table 1)
For Sumida inductor CDRH3D16, 4.7µH, DCR = 105mΩ.
∆IL1 =
VO
L1 ⋅ F
⋅
⎛⎝1
-
VO ⎞
VIN ⎠
=
1.8V
4.7µH ⋅ 1.4MHz
⋅
⎛
⎝1 -
1.8V ⎞
4.2V ⎠
= 156mA
IPKL1
=
IO
+
∆IL1
2
=
0.6A
+
0.068A
=
0.668A
PL1 = IO2 ⋅ DCR = 0.6A2 ⋅ 105mΩ = 38mW
1.8V Output Capacitor
VDROOP = 0.1V
COUT
=
3 · ∆ILOAD
VDROOP · FS
=
3 · 0.3A
0.1V · 1.4MHz
= 6.4µF; use 10µF
IRMS
=
1 · (VO) · (VIN(MAX) - VO)
2· 3
L1 · F · VIN(MAX)
=1
2·
·
3
1.8V · (4.2V - 1.8V) = 45mArms
4.7µH · 1.4MHz · 4.2V
Pesr = esr · IRMS2 = 5mΩ · (45mA)2 = 10µW
16
(PRELIMINARY INFORMATION) APS1056.2007.04.0.9
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