SwitchReg
TM
AAT1151
850kHz 700mA Synchronous Buck DC/DC Converter
1151.2005.11.1.4
1
General Description
The AAT1151 SwitchRegTM is a member of
AnalogicTech's Total Power Management ICTM
(TPMICTM) product family. The step-down switching
converter is ideal for applications where high effi-
ciency is required over the full range of output load
conditions. The 2.7V to 5.5V input voltage range
makes the AAT1151 ideal for single-cell lithium-
ion/polymer battery applications. Capable of more
than 700mA with internal MOSFETs, the current-
mode controlled IC provides high efficiency using
synchronous rectification. Fully integrated compen-
sation simplifies system design and lowers external
parts count.
The device operates at a fixed 850kHz switching fre-
quency and enters PFM mode for light load current
to maintain high efficiency across all load conditions.
The AAT1151 is available in MSOP-8 and QFN33-16
packages and is rated over the -40C to +85C tem-
perature range.
Features
V
IN
Range: 2.7V to 5.5V
Up to 95% Efficiency
High Initial Accuracy 1%
110m
R
DS(ON)
Internal Switches
<1A Shutdown Current
850kHz Switching Frequency
Fixed V
OUT
or Adjustable V
OUT
1.0V
Integrated Power Switches
Synchronous Rectification
Current Mode Operation
Internal Compensation
Stable with Ceramic Capacitors
PWM and PFM for Optimum Efficiency for All
Load Conditions
Internal Soft Start
Over-Temperature Protection
Current Limit Protection
MSOP-8 and QFN33-16 Packages
-40C to +85C Temperature Range
Applications
Cellular Phones
Digital Cameras
MP3 Players
Notebook Computers
PDAs
USB-Powered Equipment
Wireless Notebook Adapters
Typical Application
OUTPUT
3.0
H
2x 22
F
10
F
0.1
F
100
LX
VP
INPUT
FB
SGND
AAT1151
ENABLE
VCC
PGND
AAT1151
850kHz 700mA Synchronous Buck DC/DC Converter
2
1151.2005.11.1.4
Pin Descriptions
Pin Configuration
MSOP-8
QFN33-16
(Top view)
(Top view)
VP
VP
VP
NC
PGND
PGND
PGND
1
2
3
4
SGND
SGND
EN
16
15
14
13
5
6
7
8
12
11
10
9
NC
VCC
LX
LX
LX
FB
1
2
LX
PGND
LX
VP
FB
SGND
EN
VCC
1
2
3
4
8
7
6
5
Pin #
MSOP-8
QFN33-16
Symbol
Function
1
4
FB
Feedback input pin. This pin is connected to the converter output. It
is used to set the output of the converter to regulate to the desired
value via an internal resistive divider. For an adjustable output, an
external resistive divider is connected to this pin on the 1V model.
2
5, 6
SGND
Signal ground. Connect the return of all small signal components to
this pin. (See board layout rules.)
3
7
EN
Enable input pin. A logic high enables the converter; a logic low
forces the AAT1151 into shutdown mode reducing the supply current
to less than 1A. The pin should not be left floating.
4
9
VCC
Bias supply. Supplies power for the internal circuitry. Connect to input
power via low pass filter with decoupling to SGND.
5
10, 11, 12
VP
Input supply voltage for the converter power stage. Must be closely
decoupled to PGND.
6, 7
13, 14, 15
LX
Connect inductor to these pins. Switching node internally connected
to the drain of both high- and low-side MOSFETs.
8
1, 2, 3
PGND
Main power ground return pin. Connect to the output and input
capacitor return. (See board layout rules.)
8, 16
NC
Not internally connected.
EP
Exposed paddle (bottom); connect to PGND directly beneath package.
AAT1151
850kHz 700mA Synchronous Buck DC/DC Converter
1151.2005.11.1.4
3
Absolute Maximum Ratings
1
Thermal Characteristics
3
Recommended Operating Conditions
Symbol
Description
Value
Units
T
Ambient Temperature Range
-40 to 85
C
Symbol
Description
Value
Units
JA
Thermal Resistance (MSOP-8)
150
C/W
P
D
Maximum Power Dissipation (MSOP-8) (T
A
= 25C)
4
667
mW
JA
Thermal Resistance (QFN33-16)
50
C/W
P
D
Maximum Power Dissipation (QFN33-16) (T
A
= 25C)
5
2.0
W
Symbol
Description
Value
Units
V
CC
, V
P
V
CC
, V
P
to GND
6
V
V
LX
LX to GND
-0.3 to V
P
+0.3
V
V
FB
FB to GND
-0.3 to V
CC
+0.3
V
V
EN
EN to GND
-0.3 to 6
V
T
J
Operating Junction Temperature Range
-40 to 150
C
V
ESD
ESD Rating
2
- HBM
3000
V
1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at condi-
tions other than the operating conditions specified is not implied. Only one Absolute Maximum Rating should be applied at any one time.
2. Human body model is a 100pF capacitor discharged through a 1.5k
resistor into each pin.
3. Mounted on a demo board.
4. Derate 6.7mW/C above 25C.
5. Derate 20mW/C above 25C.
AAT1151
850kHz 700mA Synchronous Buck DC/DC Converter
4
1151.2005.11.1.4
Electrical Characteristics
1
V
IN
= V
CC
= V
P
= 5V, T
A
= -40C to 85C, unless otherwise noted. Typical values are at T
A
= 25C.
Symbol
Description
Conditions
Min
Typ
Max Units
V
IN
Input Voltage Range
2.7
5.5
V
V
OUT
Output Voltage Tolerance
V
IN
= V
OUT
+ 0.2 to 5.5V,
-3.0
+3.0
%
I
OUT
= 0 to 700mA
V
UVLO
Under-Voltage Lockout
V
IN
Rising
2.5
V
V
IN
Falling
1.2
V
UVLO(HYS)
Under-Voltage Lockout Hysteresis
250
mV
I
IL
Input Low Current
V
IN
= V
FB
= 5.5V
1.0
A
I
IH
Input High Current
V
IN
= V
FB
= 0 V
1.0
A
I
Q
Quiescent Supply Current
No Load, V
FB
= 0 V, V
IN
= 4.2V
210
300
A
T
A
= 25C
I
SHDN
Shutdown Current
V
EN
= 0 V, V
IN
= 5.5V
1.0
A
I
LIM
Current Limit
T
A
= 25C
1.2
A
R
DS(ON)H
High Side Switch On Resistance
T
A
= 25C
110
150
m
R
DS(ON)L
Low Side Switch On Resistance
T
A
= 25C
100
150
m
Efficiency
I
OUT
= 300mA, V
IN
= 3.5V
92
%
V
OUT
(V
OUT
*
V
IN
)
Load Regulation
V
IN
= 4.2V, I
LOAD
= 0 to 700mA
0.9
%
V
OUT
/V
OUT
Line Regulation
V
IN
= 2.7V to 5.5V
0.1
%/V
F
OSC
Oscillator Frequency
T
A
= 25C
600
850
1200
KHz
V
EN(L)
Enable Threshold Low
0.6
V
V
EN(H)
Enable Threshold High
1.4
V
T
SD
Over-Temperature Shutdown
140
C
Threshold
T
HYS
Over-Temperature Shutdown
15
C
Hysteresis
1. The AAT1151 is guaranteed to meet performance specifications over the -40C to +85C operating range and is assured by design,
characterization, and correlation with statistical process controls.
Typical Characteristics
AAT1151 Efficiency
(V
OUT
= 2.5V; L = 4.2
H)
Output Current (mA)
Efficiency (%)
50
55
60
65
70
75
80
85
90
95
100
1
10
100
1000
10000
Switching Frequency vs. Temperature
0
200
400
600
800
1000
1200
-40
-20
0
20
40
60
80
100
Temperature (
C)
Frequency (kHz)
Load and Line Regulation
Load Current (mA)
V
OUT
Error (%)
-3.0
-2.0
-1.0
0.0
1.0
2.0
3.0
1
10
100
1000
V
IN
= 3.6V
V
IN
= 4.2V
V
IN
= 2.7V
Output Voltage vs. Temperature
1.78
1.782
1.784
1.786
1.788
1.79
1.792
1.794
-40
-20
0
20
40
60
80
100
Temperature (
C)
Output Voltage (V)
Frequency vs. Input Voltage
850
860
870
880
890
2.5
3
3.5
4
4.5
5
5.5
Input Voltage (V)
Frequency (kHz)
No Load Supply Current vs. Input Voltage
2.5
3
3.5
4
4.5
5
5.5
Input Voltage (V)
Supply Current (
A)
0
50
100
150
200
250
300
T = 85
C
T = -40
C
T = 25
C
AAT1151
850kHz 700mA Synchronous Buck DC/DC Converter
1151.2005.11.1.4
5
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