AAT1157
1MHz 1.2A Buck DC/DC Converter
General Description
The AAT1157 SwitchReg™ is a member of
AnalogicTech's Total Power Management IC™
(TPMIC™) product family. The step-down switch-
ing converter is ideal for applications where fixed
frequency and low ripple are required over the full
range of load conditions. The 2.7V to 5.5V input
voltage range makes the AAT1157 ideal for single-
cell lithium-ion/polymer battery applications.
Capable of up to 1.2A with internal MOSFETs, the
current-mode controlled IC provides high efficiency
over a wide operating range. Fully integrated com-
pensation simplifies system design and lowers
external parts count. The device operates at a
fixed 1MHz switching frequency across all load
conditions.
The AAT1157 is available in the Pb-free, 16-pin
3x3mm QFN package and is rated over the -40°C
to +85°C temperature range.
Features
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SwitchReg
™
V
IN
Range: 2.7V to 5.5V
Up to 95% Efficiency
110 mΩ R
DS(ON)
Internal Switches
<1µA Shutdown Current
1MHz Buck Switching Frequency
Fixed or Adjustable V
OUT
≥
0.8V
Integrated Power Switches
Current Mode Operation
Internal Compensation
Stable with Ceramic Capacitors
Constant PWM Operation for Low Output
Ripple
Internal Soft Start
Over-Temperature Protection
Current Limit Protection
16-Pin QFN 3x3mm Package
-40°C to +85°C Temperature Range
Applications
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HDD MP3 Players
Notebook Computers
PDAs
Point-of-Load Regulation
Set Top Boxes
Smart Phones
Wireless Notebook Adapters
Typical Application
3.3V
12
U1
AAT1157
VP
VP
VP
EN
VCC
N/C
N/C
FB
LX
LX
LX
N/C
PGND
PGND
4
15
14
13
16
3
2
1
11
10
7
9
6
2.5V
R3
187k
L1
3.0µH
R1
100
C1
10µF
R4
59k
C3-C4
2x 22µF
C2
0.1µF
8
5
SGND PGND
1157.2005.11.1.4
1
ANALOGICTECH [ ADVANCED ANALOGIC TECHNOLOGIES ]
