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Teilenummer | AAT1184 |
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Beschreibung | High Voltage Step-Down Regulator | |
Hersteller | AAT | |
Logo | ||
Gesamt 19 Seiten 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
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1
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Typical Characteristics
Step-Down Converter Output Ripple
(VIN = 12V; VOUT = 3.3V; IOUT = 1mA)
12V
0V
3.31
3.30
3.29
0.2
0.1
0.0
Time (2µs/div)
Step-Down Converter Output Ripple
(VIN = 12V; VOUT = 3.3V; IOUT = 1.2A)
12V
0V
3.31
3.30
3.29
Time (1µs/div)
2
1
0
Step-Down Converter Load Transient Response
(IOUT = 0.12A to 1.2A; VIN = 12V; VOUT = 3.3V; COUT = 2x22µF)
1.5
1.2A
1.0
0.12A
0.5
0.0
3.7
3.5
3.3
3.1
2.9
Time (100µs/div)
PRODUCT DATASHEET
AAT1184
High Voltage Step-Down Regulator
Step-Down Converter Output Ripple
(VIN = 12V; VOUT = 5V; IOUT = 1mA)
12V
5.02
5.00
4.98
0V
0.2
0.1
0.0
Time (2µs/div)
Step-Down Converter Output Ripple
(VIN = 12V; VOUT = 5V; IOUT = 1.2mA)
12V
0V
5.0
4.0
3.0
2.0
1.0
0.0
5.02
5.00
4.98
Time (1µs/div)
Step-Down Converter Load Transient Response
(IOUT = 0.12A to 1.2A; VIN = 12V; VOUT = 5V; COUT = 2x22µF)
1.5
1.2A
1.0
0.12A
0.5
0.0
5.2
5.0
4.8
4.6
Time (100µs/div)
6
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PRODUCT DATASHEET
AAT1184
High Voltage Step-Down Regulator
Eq.
2:
FESR
=
2
·
π
·
1
ESR
·
COUT
The feedback and compensation networks provide a
closed loop transfer function with the highest 0dB cross-
ing frequency and adequate phase margin for system
stability. Equations 3, 4, 5 and 6 relate the compensa-
tion network’s poles and zeros to the components R2,
R3, R4, C5, C6, and C7:
Eq.
3:
FZ1
=
2
·
π
1
· R2
·
C5
Eq.
4:
FZ2
=
2
·
π
·
1
(R7 +
R4)
·
C7
1
Eq. 5: FP1 =
2 · π · R2 ·
C5 · C6
C5 + C6
Eq. 6: FP2 =
1
2 · π · R7 · C7
Components of the feedback, feed forward, compensa-
tion, and current limit networks need to be adjusted to
maintain system stability for different input and output
voltage applications as shown in Table 2.
C6
C5 R2
C7 R7 VOUT
COMP
R4
FB
R5
REF
Figure 1: AAT1184 Feedback and Compensation Networks for Type III Voltage-Mode Control Loop.
Network
Feedback
Feed-forward
Compensation
Current Limit
Components
R4
R5
C7
R7
C5
C6
R2
C4
R1
R3
R6
R8
VOUT = 3.3V
27.4kΩ
6.02kΩ
330pF
499Ω
470pF
56pF
24.3kΩ
68nF
2.32kΩ
0kΩ
Open
Open
VOUT = 5.0V
44.2kΩ
6.02kΩ
330pF
499Ω
220pF
56pF
24.3kΩ
68nF
2.32kΩ
0kΩ
Open
Open
Table 2: AAT1184 Feedback and Compensation Network Components for VOUT = 3.3V and VOUT = 5.0V.
12
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1184.2008.07.1.0
12 Page | ||
Seiten | Gesamt 19 Seiten | |
PDF Download | [ AAT1184 Schematic.PDF ] |
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