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AAT1112 Datasheet, PDF (16/19 Pages) Advanced Analogic Technologies – 1.5A, 1.4MHz Step-Down Converter | |||
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Design Example
Specifications
VO 3.3V @ 1.5A, Pulsed Load ïILOAD = 1.5A
VIN 2.7V to 4.2V (3.6V nominal)
FS 1.2MHz
TAMB 85°C in TDFN33-12 Package
Output Inductor
L1 = VO(μH) = 3.3μH; see Table 2.
For Sumida inductor CDRH4D28 3.3μH DCR = 49.2mï max.
ÎI1 =
VO
L1 â
FS
â
ââ1 -
VO1â
VIN â
=
3.3V
3.3µH â
1.2MHz
â
â
â1 -
3.3V â
4.2V â
= 179mA
IPK1
=
IO1
+
ÎI1
2
=
1.5A
+
0.089A
=
1.59A
PL1 = IO12 â
DCR = 1.5A2 â
49.2mΩ = 110mW
DATA SHEET
AAT1112
1.5A, 1.4MHz Step-Down Converter
Output Capacitor
VDROOP = 0.2V
COUT
=
3 · ÎILOAD
VDROOP · FS
=
3 · 1.5A
0.2V · 1.2MHz
= 18.8µF; use 22µF
IRMS(MAX)
=
1
2·
3
· (VOUT) · (VIN(MAX) - VOUT)
L · FS · VIN(MAX)
=
1
2·
3
·
3.3V · (4.2V - 3.3V)
3.3µH · 1.2MHz · 4.2V
= 52mArms
Pesr = esr · IRMS2 = 5mΩ · (52mA)2 = 13.3µW
Input Capacitor
Input Ripple VPP = 50mV
1
1
CIN =
â
â
VPP
IO1 + IO2
-
ESRââ
·
4
·
FS
=
â 50mV
â 1.5A
= 7.3µF; use 10µF
- 5mΩââ · 4 · 1.2MHz
I = RMS(MAX)
IO
2
= 0.75Arms
P = esr · IRMS2 = 5mΩ · (0.75A)2 = 3mW
Skyworks Solutions, Inc. ⢠Phone [781] 376-3000 ⢠Fax [781] 376-3100 ⢠sales@skyworksinc.com ⢠www.skyworksinc.com
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201972B ⢠Skyworks Proprietary Information ⢠Products and Product Information are Subject to Change Without Notice. ⢠March 15, 2013
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