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PDF AAT1184 Data sheet ( Hoja de datos )
| Número de pieza | AAT1184 | |
| Descripción | High Voltage Step-Down Regulator | |
| Fabricantes | AAT | |
| Logotipo |  |
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SwitchRegTM
General Description
The AAT1184 is a single output step-down (Buck) DC
output regulator with an integrated high side MOSFET.
The input range is 6V to 24V making it the ideal power IC
solution for consumer communications equipment oper-
ating from a low cost AC/DC adapter with 12V output.
The step-down regulator provides up to 1.2A output cur-
rent in a small package. 490kHz fixed switching fre-
quency allows small L/C filtering components.
Voltage mode control allows for optimum performance
across the entire output voltage and load range.
The controller includes programmable over-current, inte-
grated soft-start and over-temperature protection.
The AAT1184 is available in the Pb-free, low profile
12-pin TSOPJW package. The rated operating tempera-
ture range is -40°C to 85°C.
PRODUCT DATASHEET
AAT1184
High Voltage Step-Down Regulator
Features
• VIN = 6.0 to 24.0V
• VOUT Adjustable from 1.5V to 5.5V
• IOUT up to 1.2A
• Small Solution Size
• Low-Cost Non-Synchronous Solution
• Shutdown Current <35μA
• High Switching Frequency
• Voltage Mode Control
• PWM Fixed Frequency for Lowest Noise
▪ Programmable Over-Current Protection
• Over-Temperature Protection
• Internal Soft Start
• Low Profile 3x3mm TSOPJW-12 Package
• -40°C to 85°C Temperature Range
Applications
• DSL and Cable Modems
• Notebook Computers
• Satellite Set Top Box
• Wireless LAN Systems
Typical Application
VIN
6V - 24V
TSOPJW -12
IN BST
+
C1
25µF
25V
D1
BAS16
C12
1µF
25V
LX
EN
RS
AAT1184
VL
C3
2.2µF
OS
FB
COMP
GND
C2
0.1µF
L1
4.7µH
D2
B340A
R1
2.32K
C4
68nF
C7
330pF
R7
499
R2
24.3K
C5
220pF
C6
56pF
VOUT
5V/1.2A
R4
44.2k
C8
22µF
R5
6.04k
1184.2008.07.1.0
www.analogictech.com
1
1 page  
SwitchRegTM
Typical Characteristics
Step-Down Converter Efficiency vs. Load
(VOUT = 3.3V; L = 4.7µH)
100
90
80
70
60
50
40 VIN = 6V
30 VIN = 8V
20 VIN = 12V
10
VIN = 18V
VIN = 24V
0
0.1 1
10
100
1000
10000
Output Current (mA)
Step-Down Converter DC Regulation
(VOUT = 3.3V; L = 4.7µH)
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
-2.0
0.1
VIN = 6V
VIN = 8V
VIN = 12V
VIN = 18V
VIN = 24V
1 10 100 1000
Output Current (mA)
10000
Step-Down Converter Line Regulation
(VOUT = 3.3V; L = 4.7µH)
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
6
IOUT = 0.1mA
IOUT = 10mA
IOUT = 100mA
IOUT = 600mA
IOUT = 1200mA
8 10 12 14 16 18 20 22 24
Input Voltage (V)
PRODUCT DATASHEET
AAT1184
High Voltage Step-Down Regulator
Step-Down Converter Efficiency vs. Load
(VOUT = 5V; L = 4.7µH)
100
90
80
70
60
50
40 VIN = 6V
30 VIN = 8V
20 VIN = 12V
VIN = 18V
10 VIN = 24V
0
0.1 1
10
100
1000
10000
Output Current (mA)
Step-Down Converter DC Regulation
(VOUT = 5V; L = 4.7µH)
3.0
2.5
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
-2.0
-2.5
-3.0
0.1
VIN = 6V
VIN = 8V
VIN = 12V
VIN = 18V
VIN = 24V
1
10
100
1000
10000
Output Current (mA)
Step-Down Converter Line Regulation
(VOUT = 5V; L = 4.7µH)
2.0
1.5
1.0
0.5
0.0
-0.5
-1.0
-1.5
-2.0
-2.5
-3.0
-3.5
-4.0
6
IOUT = 0.1mA
IOUT = 10mA
IOUT = 100mA
IOUT = 600mA
IOUT = 1200mA
8 10 12 14 16 18 20 22 24
Input Voltage (V)
1184.2008.07.1.0
www.analogictech.com
5
5 Page 
SwitchRegTM
Applications Information
The high voltage DC/DC step-down converter provides
an output voltage from 1.5V to 5.5V. The integrated
high-side n-channel MOSFET device provides up to 1.2A
output current1. Input voltage range is 6.0V to 24.0V.
The step-down converter utilizes constant frequency
(PWM-mode) voltage mode control to achieve high oper-
ating efficiency while maintaining extremely low output
noise across the operating range. High 490kHz (nominal)
switching frequency allows small external filtering com-
ponents, achieving minimum cost and solution size.
External compensation allows the designer to optimize
the transient response while achieving stability across
the operating range.
Output Voltage and Current
The output voltage is set using an external resistor
divider as shown in Table 1. Minimum output voltage is
1.5V and maximum output voltage is 5.5V. Typical max-
imum duty cycle is 85%.
VOUT (V)
1.5
1.8
1.85
2.0
2.5
3.0
3.3
5.0
R5 = 6.04kΩ
R4 (kΩ)
9.09
12.1
12.4
14.0
19.1
24.3
27.4
44.2
Table 1: Feedback Resistor Values.
Alternatively, the feedback resistor may be calculated
using the following equation:
R4 =
(VOUT - 0.6) · R5
0.6
R4 is rounded to the nearest 1% resistor value.
Buck Regulator Output
Capacitor Selection
A 22μF ceramic output capacitor is required to filter the
inductor current ripple and supply the load transient cur-
rent for IOUT = 1.2A. The 1206 package with 10V mini-
mum voltage rating is recommended for the output
PRODUCT DATASHEET
AAT1184
High Voltage Step-Down Regulator
capacitors to maintain a minimum capacitance drop with
DC bias.
Output Inductor Selection
The step-down converter utilizes constant frequency
(PWM-mode) voltage mode control. A 4.7μH inductor
value is selected to maintain the desired output current
ripple and minimize the converter’s response time to
load transients. The peak switch current should not
exceed the inductor saturation current, the MOSFET or
the external Schottky rectifier peak current ratings.
Rectifier Selection
When the high-side switch is on, the input voltage will be
applied to the cathode of the Schottky diode. The recti-
fier's rated reverse breakdown voltage must be chosen
at least equal to the maximum input voltage of the step-
down regulator.
When the high-side switch is off, the current will flow
from the power ground to the output through the
Schottky diode and the inductor. The power dissipation
of the Schottky diode during the time-off can be deter-
mined by the following equation:
PD = IOUT · VD ·
1 - VOUT
VIN
Where VD is the voltage drop across the Schottky diode.
Input Capacitor Selection
For low cost applications, a 100μF/25V electrolytic
capacitor is selected to control the voltage overshoot
across the high side MOSFET. A small ceramic capacitor
with voltage rating at least 1.05 times greater than the
maximum input voltage is connected as close as possible
to the input pin (Pin 14) for high frequency decoupling.
Feedback and Compensation Networks
The transfer function of the Error Amplifier is dominated
by the DC Gain and the L COUT output filter of the regula-
tor. This output filter and its equivalent series resistor
(ESR) create a double pole at FLC and a zero at FESR in the
following equations:
Eq.
1:
FLC
=
2
·
π
·
1
L
·
COUT
1. Output current capability may vary and is dependent on package selection, maximum ambient temperature, airflow and PCB heatsinking.
1184.2008.07.1.0
www.analogictech.com
11
11 Page | ||
| Páginas | Total 19 Páginas | |
| PDF Descargar | [ Datasheet AAT1184.PDF ] | |
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