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PDF AAT1110 Data sheet ( Hoja de datos )
| Número de pieza | AAT1110 | |
| Descripción | Fast Transient 800mA Step-Down Converter | |
| Fabricantes | AAT | |
| Logotipo |  |
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AAT1110
Fast Transient 800mA Step-Down Converter
General Description
Features
SwitchReg™
The AAT1110 SwitchReg™ is a member of
AnalogicTech's Total Power Management IC™
(TPMIC™) product family. It is a 1.4MHz step-
• VIN Range: 2.7V to 5.5V
• VOUT Fixed or Adjustable from 0.6V to VIN
• 27µA No Load Quiescent Current
down converter with an input voltage range of 2.7V
• Output Current Up to 800mA
to 5.5V and output as low as 0.6V. Its low supply
• 1.4MHz Switching Frequency
current, small size, and high switching frequency
• 120µs Soft Start
make the AAT1110 the ideal choice for portable
• Fast Load Transient
applications.
• Over-Temperature Protection
The AAT1110 is available in either a fixed version
with internal feedback or a programmable version
with external feedback resistors. It can deliver up
to 800mA of load current while maintaining a low
27µA no load quiescent current. The 1.4MHz
• Current Limit Protection
• 100% Duty Cycle Low-Dropout Operation
• <1µA of Shutdown Current
• SC70JW-8 Package
• Temperature Range: -40°C to +85°C
switching frequency minimizes the size of external
components while keeping switching losses low.
The AAT1110 feedback and control delivers excel-
lent load regulation and transient response with a
Applications
small output inductor and capacitor.
The AAT1110 is designed to maintain high efficien-
cy throughout the operating range and provides
fast turn-on time.
www.DataSheet4U.com
•
•
•
•
Cellular Phones
Digital Cameras
Handheld Instruments
Microprocessor / DSP Core / IO Power
The AAT1110 is available in a space-saving
• PDAs and Handheld Computers
2.0x2.1mm SC70JW-8 package and is rated over
• USB Devices
the -40°C to +85°C temperature range.
Typical Application (Fixed Output Voltage)
VIN
C2
4.7μF
U1
AAT1110
3 VIN
LX 4
1 EN
OUT 2
5 AGND PGND 7
8 PGND PGND 6
L1
4.7μH
VO
C1
22μF
1110.2006.04.1.0
1
1 page  
AAT1110
Fast Transient 800mA Step-Down Converter
Typical Characteristics
Efficiency vs. Load
(VOUT = 1.8V; L = 4.7µH)
100
VIN = 2.7V
90
80
VIN = 3.6V VIN = 4.2V
70
60
50
0.1
1 10 100
Output Current (mA)
1000
DC Regulation
(VOUT = 1.8V)
1.0
VIN = 4.2V
0.5
VIN = 3.6V
0.0
-0.5
-1.0
0.1
VIN = 2.7V
1 10 100
Output Current (mA)
1000
Efficiency vs. Load
(VOUT = 2.5V; L = 6.8µH)
100
VIN = 3.0V
90
80 VIN = 4.2V VIN = 5.0V
VIN = 3.6V
70
60
50
0.1
1 10 100
Output Current (mA)
1000
DC Regulation
(VOUT = 2.5V)
2.0
1.5
VIN = 5.0V
1.0
0.5 VIN = 4.2V
0.0
-0.5 VIN = 3.6V
-1.0
-1.5
-2.0
0.1
1
10
VIN = 3.0V
100
1000
Output Current (mA)
Efficiency vs. Load
(VOUT = 3.3V; L = 6.8µH)
100
VIN = 3.6V
90
80 VIN = 5.0V
VIN = 4.2V
70
60
50
0.1
1 10 100
Output Current (mA)
1000
1.0
0.5
0.0
-0.5
-1.0
0.1
DC Regulation
(VOUT = 3.3V; L = 6.8µH)
VIN = 4.2V
VIN = 5.0V
1 10 100
Output Current (mA)
1000
1110.2006.04.1.0
5
5 Page 
AAT1110
Fast Transient 800mA Step-Down Converter
Applications Information
Inductor Selection
The step-down converter uses peak current mode
control with slope compensation to maintain stability
for duty cycles greater than 50%. The output induc-
tor value must be selected so the inductor current
down slope meets the internal slope compensation
requirements. The internal slope compensation for
the adjustable and low-voltage fixed versions of the
AAT1110 is 0.24A/µsec. This equates to a slope
compensation that is 75% of the inductor current
down slope for a 1.5V output and 4.7µH inductor.
m
=
0.75 ⋅
L
VO
=
0.75 ⋅ 1.5V
4.7μH
=
0.24
A
μsec
This is the internal slope compensation for the
adjustable (0.6V) version or low-voltage fixed ver-
sions. When externally programming the 0.6V ver-
sion to 2.5V, the calculated inductance is 7.5µH.
L=
0.75 ⋅ VO
m
=
0.75 ⋅ VO
A
≈
3
μsec
A
⋅
VO
0.24A μsec
=
3
μsec
A
⋅ 2.5V = 7.5μH
In this case, a standard 6.8µH value is selected.
For high-voltage fixed versions (≥2.5V), m = 0.48A/
µsec. Table 1 displays inductor values for the
AAT1110 fixed and adjustable options.
Manufacturer's specifications list both the inductor
DC current rating, which is a thermal limitation, and
the peak current rating, which is determined by the
saturation characteristics. The inductor should not
show any appreciable saturation under normal load
conditions. Some inductors may meet the peak and
average current ratings yet result in excessive loss-
es due to a high DCR. Always consider the losses
associated with the DCR and its effect on the total
converter efficiency when selecting an inductor.
The 4.7µH CDRH3D16 series inductor selected
from Sumida has a 105mΩ maximum DCR and a
900mA DC current rating. At full load, the inductor
DC loss is 67mW which gives a 4.0% loss in effi-
ciency for a 800mA, 2.5V output.
Input Capacitor
Select a 4.7µF to 22µF X7R or X5R ceramic capac-
itor for the input. To estimate the required input
capacitor size, determine the acceptable input rip-
ple level (VPP) and solve for C. The calculated
value varies with input voltage and is a maximum
when VIN is double the output voltage.
VO
VIN
·
⎛⎝1 -
VO ⎞
VIN ⎠
CIN =
⎛ VPP
⎝ IO
- ESR⎞⎠ · FS
VO
VIN
·
⎛⎝1 -
VO ⎞
VIN ⎠
=
1
4
for
VIN
=
2
×
VO
1
CIN(MIN) = ⎛ VPP
⎝ IO
- ESR⎞⎠ · 4 · FS
Always examine the ceramic capacitor DC voltage
coefficient characteristics when selecting the prop-
er value. For example, the capacitance of a 10µF,
6.3V, X5R ceramic capacitor with 5.0V DC applied
is actually about 6µF.
Configuration
0.6V Adjustable With
External Feedback
Fixed Output
1110.2006.04.1.0
Output Voltage
1V, 1.2V
1.5V, 1.8V
2.5V, 3.3V
0.6V to 3.3V
Table 1: Inductor Values.
Inductor
2.2µH
4.7µH
6.8µH
4.7µH
11
11 Page | ||
| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet AAT1110.PDF ] | |
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