850kHz 1A Buck DC/DC Converter
General Description
The AAT1152 SwitchReg is a step-down switching
converter ideal for applications where high efficien-
cy, small size, and low ripple are critical. Able to
deliver 1A with internal power MOSFETs, the cur-
rent mode controlled IC is internally compensated
for simplified system design and low external parts
count.
The AAT1152 features a Power-OK (POK) function
which monitors the output, alerting the system if
the output voltage falls out of regulation.
The AAT1152 is available in a Pb-free MSOP-8
package and is rated over the -40°C to +85°C tem-
perature range.
AAT1152
Features
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
SwitchReg
™
5.5V Max Supply Input
Fixed or Adjustable V
OUT
1.0V to 4.2V
1A Output Current
Integrated Low On Resistance Power Switches
Up to 95% Efficiency
Power-OK Signal
Internally Compensated Current Mode Control
High Initial Accuracy: ±1%
850kHz Switching Frequency
Constant Pulse Width Modulation (PWM)
Mode
Low Output Ripple with Light Load
Internal Soft Start
Current Limit Protection
Over-Temperature Protection
MSOP-8 Package
-40°C to +85°C Temperature Range
Applications
•
•
•
•
•
Cable/DSL Modems
Computer Peripherals
High Efficiency Conversion from 5V or 3.3V
Supply
Network Cards
Set-Top Boxes
Typical Application
INPUT
100k
10μF
VP
AAT1152
POK
FB
4.1μH
LX
ENABLE
100Ω
VCC
SGND
0.1μF
PGND
3 x 22μF
OUTPUT
1152.2006.09.1.7
1
850kHz 1A Buck DC/DC Converter
Pin Descriptions
Pin #
1
2
3
4
5
6
7
8
AAT1152
Symbol
FB
SGND
EN
VCC
VP
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-OK 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
VCC
1
8
PGND
POK
LX
VP
1
2
7
2
3
6
4
5
2
1152.2006.09.1.7
850kHz 1A Buck DC/DC Converter
Absolute Maximum Ratings
1
T
A
= 25°C, unless otherwise noted.
Symbol
V
CC
, V
P
V
LX
V
FB
V
EN
, V
POK
T
J
T
LEAD
V
ESD
AAT1152
Description
VCC, VP 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
2
- HBM
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
Units
V
V
V
V
°C
°C
V
Thermal Characteristics
3
Symbol
Θ
JA
P
D
Description
Maximum Thermal Resistance (MSOP-8)
Maximum Power Dissipation (MSOP-8)
Value
150
833
Units
°C/W
mW
Recommended Operating Conditions
Symbol
T
Description
Ambient Temperature Range
Rating
-40 to +85
Units
°C
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 1.5kΩ resistor into each pin.
3. Mounted on a demo board.
1152.2006.09.1.7
3
850kHz 1A Buck DC/DC Converter
Electrical Characteristics
V
IN
= V
CC
= V
P
= 5V, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= 25°C.
Symbol
V
IN
V
OUT
I
LIM
I
Q
ΔV
OUT
(V
OUT
*ΔV
IN
)
ΔV
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
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
Under-Voltage Lockout
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
T
A
= 25°C
No Load, V
FB
= 0
V
IN
= 4.2V, I
LOAD
= 0 to 1A
V
IN
= 2.7V to 5.5V
T
A
= 25°C
T
A
= 25°C
T
A
= 25°C
V
IN
= 2.7V to 5.5V
V
IN
= 2.7V 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
1
90
88
4
Under-Voltage Lockout Hysteresis
Over-Temperature Shutdown
Threshold
Over-Temperature Shutdown
Hysteresis
Shutdown Current
V
EN
= 0, V
IN
= 5.5V
V
FB
Ramping Up
Power-OK Threshold
V
FB
Ramping Down
Power-OK Pull-Down
On Resistance
μA
% of
V
FB
Ω
4
1152.2006.09.1.7
850kHz 1A Buck DC/DC Converter
Typical Characteristics
Efficiency vs. Output Current
(V
OUT
= 1.5V)
100
80
170
AAT1152
High Side R
DS(ON)
vs. Temperature
2.7V
R
DS(ON)
(mΩ)
150
3.6V
2.7V
Efficiency (%)
60
130
110
90
70
-20
4.2V
40
20
0
10
100
1000
3.6V
4.2V
5.5V
0
20
40
60
80
100
120
Output Current (mA)
Temperature (°C)
Low Side R
DS(ON)
vs. Temperature
170
150
130
120
R
DS(ON)
vs. Input Voltage
R
DS(ON)
(mΩ)
R
DS(ON)
(mΩ)
High Side
110
100
90
80
2.5
3
3.5
4
4.5
5
5.5
130
110
90
70
-20
3.6V
2.7V
5.5V
4.2V
0
20
40
60
80
100
120
Low Side
Temperature (°C)
Input Voltage (V)
Enable Threshold vs. Input Voltage
1.2
3.5
Oscillator Frequency Variation vs.
Supply Voltage
Enable Threshold (V)
1.1
1
Variation (%)
V
EN(H)
2.5
1.5
0.5
-0.5
-1.5
0.9
0.8
V
EN(L)
0.7
2.5
3
3.5
4
4.5
5
5.5
2.5
3
3.5
4
4.5
5
5.5
Input Voltage (V)
Supply Voltage (V)
1152.2006.09.1.7
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