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PDF AAT2687 Data sheet ( Hoja de datos )
| Número de pieza | AAT2687 | |
| Descripción | PMIC Solution | |
| Fabricantes | Skyworks | |
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DATA SHEET
AAT2687
PMIC Solution for 24V Systems
with 2 High Performance Step-Down Converters
General Description
The AAT2687 provides two independently regulated DC
outputs; consisting of a high voltage step-down regula-
tor and a low input voltage low dropout (LDO) regulator.
The PMIC is optimized for low-cost 12V adapter inputs,
making the device the ideal system-on-a-chip power
solution for consumer communications equipment.
Channel 1 is a step-down regulator with an input voltage
range 6.0 to 24V, providing up to 4.5A output current.
490kHz fixed switching frequency allows small L/C filter-
ing components. Channel 1 utilizes voltage mode control
configured for optimum performance across the entire
output voltage and load range.
Channel 2 is a low-dropout (LDO) regulator providing up
to 600mA output current. The device provides extremely
low output noise, low quiescent current and excellent
transient response.
The controller includes integrated cycle-by-cycle over-
current protection, soft-start and over-temperature dis-
able features. Independent input and enable pins pro-
vide maximum design flexibility.
The AAT2687 is available in the Pb-free, 4x5mm 24-pin
TQFN package. The rated operating temperature range is
-40C to 85C.
Features
• 2-Output Step-Down Converters:
▪ Channel 1 Step-Down: VIN1 = 6V to 24V
• VOUT1 Adjustable from 1.5V to 5.5V
• IOUT1 up to 4.5A
• High Switching Frequency
• Voltage Mode Control
• PWM Fixed Frequency for Low-Ripple
▪ Channel 2 (LDO): VIN2 = 2.7V to 5.5V
• IOUT2 up to 600mA
• 1V Dropout Voltage at 600mA
• High Accuracy ±1.5%
• Small Solution Size
▪ System On a Chip
▪ Ultra-small External L/C
• Shutdown Current <35μA
• Independent Enable Pins
• Programmable Over-Current Protection
• Over-Temperature Protection
• Internal Soft Start
• 4x5mm 24-Pin TQFN Low Profile Thermally Enhanced
Package
• -40°C to 85°C Temperature Range
Applications
• DSL and Cable Modems
• Notebook Computers
• Satellite Settop Box
• Wireless LAN Systems
Typical Application
VIN1
6.0V - 24.0V
J1 2
1
C3
0.1µF
D1
BAS16
C14
2.2µF
+ C1
220µF
25V
VIN2
C13
1µF
25V
C2
2.2µF
LX1
BST
VL1 RS1
OS1
IN1 FB1
L1
4.7µH 5.3A
D2
R2 C4
2k 220nF
C10
2.2nF
R5
450
VOUT1
3.3V/4.5A
R3
8.87k
C7 C8 C9
22µF 22µF 22µF
COMP1
AAT2687
EN1
OUT2
IN2
EN2 GND
TQFN45-24
R1 C5
3.92K 2.2nF
C6
VOUT2 150pF
1.8V/600mA
R4
1.96k
C12
2.2µF
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202033A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 8, 2012
1
1 page  
DATA SHEET
AAT2687
PMIC Solution for 24V Systems
with 2 High Performance Step-Down Converters
Typical Characteristics—Channel 1
Step-Down Converter Efficiency vs. Load Current
100
90
80
70
60
50
40
30
20
10
0
0.001
0.01
0.1
VIN1 = 6V
VIN1 = 7V
VIN1 = 8V
VIN1 = 12V
VIN1 = 18V
VIN1 = 24V
1 10
Load Current (A)
Step-Down Converter Load Regulation
vs. Load Current
2
1.5
1
0.5
0
-0.5
-1
-1.5
-2
0.001
VIN1 = 6V
VIN1 = 7V
VIN1 = 8V
VIN1 = 12V
VIN1 = 18V
VIN1 = 24V
0.01
0.1
1
10
Load Current (A)
Step-Down Converter Line Regulation
vs. Load Current
2
IOUT1 = 0.1µA
1.5 IOUT1 = 2.25A
1 IOUT1 = 3.5A
IOUT1 = 4mA
0.5 IOUT1 = 4.5A
0
-0.5
-1
-1.5
-2
6
9 12 15 18 21 24
Input Voltage (V)
No Load Step-Down Converter Input Current
vs. Input Voltage
650
625
600
575
550
525
500
475
450
6
85°C
25°C
-40°C
9 12 15 18 21 24
Input Voltage (V)
Step-Down Converter Switching Frequency
vs. Input Voltage
(VOUT1 = 3.3V; IOUT1 = 4.5A)
8
85°C
6 25°C
4 -40°C
2
0
-2
-4
-6
-8
6
8 10 12 14 16 18 20 22 24
Input Voltage (V)
Step-Down Converter Output Voltage
vs. Temperature
(VOUT = 3.3V; IOUT1 = 4.5A; COUT1 = 66µF; L = 4.7µH; VIN1 = 12V)
1
0.75
0.5
0.25
0
-0.25
-0.5
-0.75
-1
-40 -15 10 35 60 85
Temperature (°C)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202033A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 8, 2012
5
5 Page 
DATA SHEET
AAT2687
PMIC Solution for 24V Systems
with 2 High Performance Step-Down Converters
Channel 1 Feedback and
Compensation Networks
C6
C5 R1
C10
R5 VOUT1
COMP1
R3
FB1
R4
stability. Equation 3, 4, 5 and 6 relate the compensation
network’s poles and zeros to the components R1, R3,
R5, C5, C6, and C10:
Eq.
3:
FZ1
=
2
·
π
1
· R1
·
C5
Eq.
4:
FZ1
=
2
·
π
·
1
(R3 +
R5)
·
C10
Eq. 5: FP1 =
1
2 · π · R1 ·
C5 · C6
C5 + C6
Eq. 6: FP2 =
1
2 · π · R5 · C10
REF
Figure 1: AAT2687 Feedback and Compensation
Networks for Type III Voltage-Mode Control Loop.
Components of the feedback, feed forward, compensa-
tion, and current limit networks need to be adjusted to
maintain the systems stability for different input and
output voltages applications as shown in Table 1.
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
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
Channel 1 Thermal Protection
The AAT2687 has an internal thermal protection circuit
which will turn on when the device die temperature
exceeds 135°C. The internal thermal protection circuit
will actively turn off the high side regulator output
device to prevent the possibility of over temperature
damage. The Buck regulator output will remain in a
shutdown state until the internal die temperature falls
back below the 135°C trip point. The combination and
interaction between the short circuit and thermal protec-
tion systems allows the Buck regulator to withstand
indefinite short-circuit conditions without sustaining per-
manent damage.
Network
Feedback
Feed-forward
Compensation
Current Limit
Components
R4
R3
C10
R5
C5
C6
R1
C4
R2
R6
R7
R8
VOUT =3.3V
VIN = 6V-24V
1.96kΩ
8.87kΩ
2.2nF
453Ω
2.2nF
150pF
3.92kΩ
220nF
2kΩ
Open
2kΩ
165kΩ
VOUT = 5.0V
VIN = 6V-24V
1.96kΩ
8.87kΩ
2.2nF
453Ω
2.2nF
150pF
3.92kΩ
220nF
2kΩ
Open
2kΩ
165kΩ
Table 1: AAT2687 Feedback, Compensation, and Current Limit Components For VOUT = 3.3V and VOUT = 5.0V.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
202033A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • June 8, 2012
11
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet AAT2687.PDF ] | |
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