AAT1157
1MHz 1.2A Buck DC/DC Converter
1157.2005.11.1.4 1
SwitchReg
™
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
•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
• HDD MP3 Players
• Notebook Computers
• PDAs
• Point-of-Load Regulation
• Set Top Boxes
• Smart Phones
• Wireless Notebook Adapters
Typical Application
3.0µH
L1
2x 22µF
C3-C4
10µF
C1
100
R1
0.1µF
C2
2.5V3.3V
187k
R3
59k
R4
LX
14
N/C
6
EN
7
VCC
9
VP
10
N/C
8
LX
13
PGND
3
VP
12
VP
11
FB
4
LX
15
PGND
2
PGND
1
SGND
5
N/C
16
AAT1157
U1