AAT1162 View Datasheet(PDF) - Advanced Analogic Technologies
Part Name
Description
MFG CO.
'AAT1162' PDF : 18 Pages View PDF
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PRODUCT DATASHEET
AAT1162
12V, 1.5A Step-Down DC/DC Converter
Design Example
Specifications
VOUT
VIN
FOSC
TAMB
5V @ 1.5A, Pulsed Load ΔILOAD = 1.5A
12V nominal
800kHz
85°C in TDFN34-16 Package
Output Inductor
L=
VOUT
3.3
· 3.8µH = 5.75µH; use 4.7µH (see Table 2)
ΔIL = 0.32 · ILOAD = 480mA
For Cooper Bussman inductor DR73-4R7-R 4.7μH DCR = 29.7mW max.
ΔI1 =
VOUT
L1 ⋅ FOSC
⋅
⎛⎝1
-
VO1
VIN
⎞
⎠
=
5V
4.7µH ⋅ 800kHz
⋅
⎛⎝1
-
5V ⎞
12V⎠
=
480mA
IPK1
=
ILOAD
+
ΔI1
2
=
1.5A
+
0.480A
=
1.98A
PL1
=
I2
LOAD
⋅
DCR
=
3A2
⋅
13mΩ
=
117mW
Output Capacitor
VDROOP = 0.2V
COUT
= 3 · ΔILOAD
VDROOP · FOSC
=
3 · 1.5A
0.2V · 800kHz
= 28µF; use 22µF
I = RMS(MAX)
1 · (VOUT) · (VIN(MAX) - VOUT) = 1 ·
2· 3
L · FOSC · VIN(MAX)
2· 3
5V · (12V - 5V)
4.7µH · 800kHz · 12V
= 139mArms
Pesr = esr · IRMS2 = 5mΩ · (277mA)2 = 384µW
Input Capacitor
Input Ripple VPP = 50mV
1
1
CIN =
⎛
⎝
VPP
ILOAD
-
ESR⎞⎠ · 4
· FOSC
=
⎛ 50mV
⎝ 1.5A
- 5mΩ⎞⎠ · 4 · 800kHz
= 11µF; use 10µF
I = RMS(MAX)
ILOAD
2
=
0.75Arms
P = esr · IRMS2 = 5mΩ · (0.75A)2 = 2.81mW
16
www.analogictech.com
1162.2008.01.1.3
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