850kHz 1A Synchronous Buck DC/DC Converter
General Description
The AAT1152 SwitchReg™ is a member of
AnalogicTech™'s Total Power Management™ IC
product family. The Step-down switching converter
is ideal for applications where high efficiency, small
size, and low ripple are critical. Able to deliver 1A
with internal Power MOSFETs, the current-mode
controlled IC provides high efficiency using syn-
chronous rectification. Fully internally compensat-
ed, the AAT1152 simplifies system design and low-
ers external part count.
The AAT1152 features a Power Good (POK) func-
tion which monitors the output, alerting the system
if the output voltage falls out of regulation.
The AAT1152 is available in MSOP-8 package,
rated over -40 to 85°C.
AAT1152
Features
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
SwitchReg
™
5.5V max supply input
Fixed output voltage: 1.1V–4.2V with 100 mV
increment
1A output current
Integrated low on resistance power switches
Synchronous rectification
Up to 95% efficiency
Power Good signal
Internally compensated current mode control
High initial accuracy: ±1%
850kHz switching frequency
Constant PWM mode
Low output ripple with light load
Internal softstart
Current limit protection
Over-Temperature protection
MSOP-8 package
Preliminary Information
Applications
•
•
•
•
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Computer Peripherals
Set Top Boxes
Network Cards
Cable/DSL Modems
High efficiency conversion from 5V or 3.3V
supply
Typical Application
INPUT
100k
10µF
V
P
AAT1152
POK
FB
4.1µH
LX
ENABLE
100Ω
V
CC
OUTPUT
SGND
0.1µF
P
GND
47µF
1152.2003.01.0.9
1
850kHz 1A Synchronous Buck DC/DC Converter
Pin Descriptions
Pin #
1
2
3
4
5
6
7
8
AAT1152
Symbol
FB
SGND
EN
V
CC
V
P
LX
POK
PGND
Function
Feedback input pin
Signal Ground
Converter enable pin
Small Signal Filtered Bias Supply
Input supply for converter power stage
Inductor connection pin
Power Good indicator. Open-drain output is low when V
OUT
falls
out of regulation.
Power ground return for output stage
Pin Configuration
MSOP-8
FB
SGND
EN
V
CC
1
2
8
7
3
4
6
5
PGND
POK
LX
V
P
1
2
2
1152.2003.01.0.9
850kHz 1A Synchronous Buck DC/DC Converter
Absolute Maximum Ratings
Symbol
V
CC
, V
P
V
LX
V
FB
V
EN
, V
POK
T
J
T
LEAD
V
ESD
AAT1152
(T
A
=25°C unless otherwise noted)
Value
6
-0.3 to V
P
+0.3
-0.3 to V
CC
+0.3
-0.3 to 6
-40 to 150
300
3000
Description
V
CC
, V
P
to GND
LX to GND
FB to GND
POK, EN to GND
Operating Junction Temperature Range
Maximum Soldering Temperature (at leads, 10 sec)
ESD Rating
1
- HBM
Units
V
V
V
V
°C
°C
V
Note: Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at con-
ditions other than the operating conditions specified is not implied. Only one Absolute Maximum rating should be applied at any one time.
Note 1: Human body model is a 100pF capacitor discharged through a 1.5K resistor into each pin.
Thermal Characteristics
Symbol
Θ
JA
P
D
Description
Maximum Thermal Resistance (MSOP-8)
Maximum Power Dissipation (MSOP-8)
2
2
Value
150
833
Units
°C/W
mW
Note 2: Mounted on a demo board.
Recommended Operating Conditions
Symbol
T
Description
Ambient Temperature Range
Rating
-40 to +85
Units
°C
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850kHz 1A Synchronous Buck DC/DC Converter
Electrical Characteristics
values are at T
A
= 25°C)
Symbol
V
IN
V
OUT
I
LIM
I
Q
∆V
OUT
(V
OUT
*∆V
IN
)
∆V
OUT
/V
OUT
F
OSC
R
DSON(H)
R
DSON(L)
V
EN(H)
V
EN(L)
I
EN
V
UVLO
V
UVLO(hys)
T
SD
T
HYS
I
SHDN
V
TH(POK)
R
POK
AAT1152
(V
IN
= V
CC
= V
P
= 5V, T
A
= -40 to 85°C unless otherwise noted. Typical
Description
Operation Voltage
DC Output Voltage Tolerance
Current Limit
Quiescent Supply Current
Load Regulation
Line Regulation
Oscillator frequency
High-side Switch On-resistance
Low-side Switch On-resistance
Enable input high voltage
Enable input low voltage
Enable Pin Leakage Current
Undervoltage Lockout
Undervoltage Lockout Hysteresis
Over Temp Shutdown Threshold
Over Temp Shutdown Hysteresis
Shutdown current
Power Good Threshold
Power Good Pull-Down
On-Resistance
Conditions
I
OUT
= 500mA
T
A
= 25°C
Full temp
Min
2.7
-1.0
-2.0
1.2
Typ
Max
5.5
+1.0
+2.0
Units
V
%
A
µA
%
%/V
kHz
mΩ
mΩ
V
V
µA
V
mV
°C
°C
µA
% of
V
FB
Ω
T
A
= 25°C
No load, V
FB
= 0
V
IN
= 4.2V, I
LOAD
= 0 to 1A
V
IN
= 2.7 to 5.5V
T
A
= 25°C
T
A
= 25°C
T
A
= 25°C
V
IN
= 2.7 to 5.5V
V
IN
= 2.7 to 5.5V
V
EN
= 5.5V
V
IN
rising
V
IN
falling
700
160
3
0.2
850
110
100
300
1000
150
150
0.6
1
2.5
1.4
1.2
250
140
15
V
EN
= 0, V
IN
= 5.5V
V
FB
Ramping Up
V
FB
Ramping Down
1
90
88
4
4
1152.2003.01.0.9
850kHz 1A Synchronous Buck DC/DC Converter
Typical Characteristics
High Side R
DS(ON)
vs. Temperature
170
150
170
AAT1152
Low Side R
DS(ON)
vs. Temperature
3.6V
2.7V
R
DS(ON)
(mΩ)
150
130
110
90
70
-20
R
DS(ON)
(mΩ)
130
110
90
70
-20
3.6V
2.7V
5.5V
4.2V
0
20
40
60
80
100
120
4.2V
5.5V
0
20
40
60
80
100
120
Temperature (°C)
Temperature (°C)
R
DS(ON)
vs. Input Voltage
130
1.2
120
Enable Threshold vs. Input Voltage
Enable Threshold (V)
High Side
R
DS(ON)
(mΩ)
110
100
1.1
V
EN
(H)
1
0.9
0.8
90
80
2.5
3
3.5
4
Low Side
V
EN
(L)
4.5
5
5.5
0.7
2.5
3
3.5
4
4.5
5
5.5
Input Voltage (V)
Input Voltage (V)
Oscillator Frequency Variation vs.
Supply Voltage
3.5
2.5
Oscillator Frequency Variation vs. Temperature
V
IN
=3.6V
10
6
Variation (%)
1.5
0.5
-0.5
-1.5
2.5
3
3.5
4
4.5
5
5.5
Variation (%)
2
-2
-6
-10
-20
0
20
40
60
80
100
Supply Voltage (V)
Temperature (°C)
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PCB Design
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