DR73-4R7-R [SKYWORKS]
12V, 1.5A Step-Down DC/DC Converter; 12V ， 1.5A降压型DC / DC转换器
| 型号： | DR73-4R7-R |
| 厂家： | 
SKYWORKS SOLUTIONS INC. |
| 描述： | 12V, 1.5A Step-Down DC/DC Converter |
| 文件： | 总19页 (文件大小：2637K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
DATA SHEET
AAT1162
12V, 1.5A Step-Down DC/DC Converter
Features
General Description
The AAT1162 is an 800kHz high efficiency step-down
DC/DC converter. With a wide input voltage range of
4.0V to 13.2V, the AAT1162 is an ideal choice for dual-
cell Lithium-ion battery-powered devices and mid-pow-
er-range regulated 12V-powered industrial applications.
The internal power switches are capable of delivering up
to 1.5A to the load.
• Input Voltage Range: 4.0V to 13.2V
• Up to 1.5A Load Current
• Fixed or Adjustable Output:
Output Voltage: 0.6V to VIN
▪
• Low 150μA No-Load Operating Current
• Less than 1μA Shutdown Current
• Up to 96% Efficiency
• Integrated Power Switches
• 800kHz Switching Frequency
• Soft Start Function
• Short-Circuit and Over-Temperature Protection
• Minimum External Components
• TDFN34-16 Package
The AAT1162 is a highly integrated device, simplifying
system-level design. Minimum external components are
required for the converter.
The AAT1162 optimizes efficiency throughout the entire
load range. It operates in a combination PWM/Light Load
mode for improved light-load efficiency. The high switch-
ing frequency allows the use of small external compo-
nents. The low current shutdown feature disconnects the
load from VIN and drops shutdown current to less than
1μA.
• Temperature Range: -40°C to +85°C
Applications
• Distributed Power Systems
• Industrial Applications
• Laptop Computers
• Portable DVD Players
• Portable Media Players
• Set-Top Boxes
The AAT1162 is available in a Pb-free, space-saving,
thermally-enhanced 16-pin TDFN34 package and is
rated over an operating temperature range of -40°C to
+85°C.
• TFT LCD Monitors and HDTVs
Typical Application
Output:
L1
0.6V min,
1.5A max
Input:
4.0V ~ 13.2V
IN
LX
FB
2.2 to 4.7μH
C2
0.1μF
R4
10
C6
10μF
EN
DGND
AIN
AAT1162
C8
1μF
C3
22μF
PGND
AGND
COMP
LDO
R5
24k
C7
330pF
C9
1μF
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DATA SHEET
AAT1162
12V, 1.5A Step-Down DC/DC Converter
Pin Descriptions
Pin #
Symbol Function
Power switching node. LX is the drain of the internal P-channel switch and N-channel synchronous recti-
fier. Connect the output inductor to the two LX pins and to EP2. A large exposed copper pad under the
package should be used for EP2.
1, 2, EP2
3, 12
LX
N/C
IN
Not connected.
Power source input. Connect IN to the input power source. Bypass IN to DGND with a 22μF or greater
capacitor. Connect both IN pins together as close to the IC as possible. An additional 100nF ceramic
capacitor should also be connected between the two IN pins and DGND, pin 6
4, 5
Exposed Pad 1 Digital Ground, DGND. The exposed thermal pad (EP1) should be connected to board
ground plane and pins 6, 13, and 14. The ground plane should include a large exposed copper pad under
the package for thermal dissipation (see package outline).
Internal analog bias input. AIN supplies internal power to the AAT1162. Connect AIN to the input source
voltage and bypass to AGND with a 0.1μF or greater capacitor. For additional noise rejection, connect to
the input power source through a 10 or lower value resistor.
Internal LDO bypass node. The output voltage of the internal LDO is bypassed at LDO. The internal
circuitry of the AAT1162 is powered from LDO. Do not draw external power from LDO. Bypass LDO to
AGND with a 1μF or greater capacitor.
Output voltage feedback input. FB senses the output voltage for regulation control. For fixed output
versions, connect FB to the output voltage. For adjustable versions, drive FB from the output voltage
through a resistive voltage divider. The FB regulation threshold is 0.6V.
6, 13,
14, EP1
DGND
AIN
7
8
9
LDO
FB
10
11
COMP
AGND
Control compensation node. Connect a series RC network from COMP to AGND, R = 51k and C = 150pF.
Analog signal ground. Connect AGND to PGND at a single point as close to the IC as possible.
Active high enable input. Drive EN high to turn on the AAT1162; drive it low to turn it off. For automatic
startup, connect EN to IN through a 4.7k resistor. EN must be biased high, biased low, or driven to a
logic level by an external source. Do not let the EN pin float when the device is powered.
15
16
EN
PGND
Power ground. Connect AGND to PGND at a single point as close to the IC as possible.
Pin Configuration
TDFN34-16
(Top View)
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
PGND
EN
LX
LX
EP2
EP1
N/C
IN
DGND
DGND
N/C
IN
AGND
DGND
AIN
LDO
COMP
FB
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DATA SHEET
AAT1162
12V, 1.5A Step-Down DC/DC Converter
Absolute Maximum Ratings1
Symbol
Description
Value
Units
VIN, VAIN
VLX
VFB
VEN
TJ
Input Voltage
LX to GND Voltage
FB to GND Voltage
EN to GND Voltage
-0.3 to 14
V
V
V
V
°C
-0.3 to VIN + 0.3
-0.3 to VIN + 0.3
-0.3 to VIN + 0.3
-40 to 150
Operating Junction Temperature Range
Thermal Information3
Symbol
Description
Maximum Power Dissipation4
Thermal Resistance
Value
Units
PD
JA
2.7
37
W
°C/W
1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions other than the operating conditions
specified is not implied. Only one Absolute Maximum Rating should be applied at any one time.
2. Based on long-term current density limitation.
3. Mounted on an FR4 board.
4. Derate 2.7mW/°C above 25°C.
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DATA SHEET
AAT1162
12V, 1.5A Step-Down DC/DC Converter
Electrical Characteristics1
4.0V < VIN < 13.2V. CIN = COUT = 22μF; L = 2.2 or 3.8μH, TA = -40°C to +85°C, unless otherwise noted. Typical values
are at TA = 25°C.
Symbol Description
Conditions
Min Typ Max Units
VIN
Input Voltage Range
4.0
13.2
4.0
V
Rising
VUVLO
Input Under-Voltage Lockout
V
Hysteresis
No Load
VEN = GND
0.3
150
IQ
ISHDN
Supply Current
Shutdown Current
300
1
μA
μA
0.94
VIN
2.5
VOUT
Output Voltage Range
Output Voltage Accuracy
Line Regulation
0.6
V
%
VOUT
VOUT
VOUT/VIN
VOUT
IOUT = 0A to 1.5A
-2.5
/
VIN = 4.5V to 13.2V
0.023 0.100
0.4
%/V
/
Load Regulation
VIN = 12V, VOUT = 5V, IOUT = 0A to 1.5A
%
V
IOUT
VFB
Feedback Reference Voltage (adjustable version) No Load, TA = 25°C
0.59 0.60
0.61
0.2
Adjustable Version
Fixed Version
IFBLEAK
FOSC
FB Leakage Current
VOUT = 1.2V
μA
2
0.8
200
PWM Oscillator Frequency
Foldback Frequency
Maximum Duty Cycle
Minimum Turn-On Time
Soft-Start Time
0.6
1
MHz
kHz
%
ns
ms
DC
TON
TS
94
100
2
VIN = 12V
VIN = 6V
VIN = 12V
VIN = 6V
0.12
0.15
0.06
0.08
90
RDS(ON)H
RDS(ON)L
P-Channel On Resistance
N-Channel On Resistance
ILIM
ILXLEAK
TSD
THYS
VIL
Efficiency
PMOS Current Limit
LX Leakage Current
Over-Temperature Shutdown Threshold
Over-Temperature Shutdown Hysteresis
EN Logic Low Input Threshold
EN Logic High Input Threshold
EN Input Current
VIN = 12V, VOUT = 5V, IOUT = 1.5A
%
A
μA
°C
°C
V
4.0
6.0
VIN = 13.2V, VLX = 0 to VIN
1
140
25
0.4
1.0
VIH
IEN
1.4
-1.0
V
μA
VEN = 0V, VEN = 13.2V
1. The AAT1162 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured by design, characterization, and correla-
tion with statistical process controls.
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DATA SHEET
AAT1162
12V, 1.5A Step-Down DC/DC Converter
Typical Characteristics
Test circuit of Figure 2, unless otherwise specified.
Efficiency vs. Output Current
(VOUT = 5V)
Load Regulation
(VOUT = 5V)
100
90
80
70
60
50
0.5
VIN = 6V
0.4
VIN = 8.4V
0.3
VIN = 10V
0.2
VIN = 12V
VIN = 13.2V
0.1
0
VIN = 6V
40
-0.1
-0.2
-0.3
-0.4
-0.5
VIN = 8.4V
VIN = 10V
VIN = 12V
VIN = 13.2V
30
20
10
0
0.0001
0.001
0.01
0.1
1
10
0.0001
0.001
0.01
0.1
1
10
Output Current (A)
Output Current (A)
Efficiency vs. Output Current
(VOUT = 3.3V)
Load Regulation
(VOUT = 3.3V)
0.6
0.4
100
VIN = 5V
90
80
70
60
50
40
30
20
10
0
VIN = 8.4V
VIN = 10V
VIN = 12V
VIN = 13.2V
0.2
0.0
VIN = 5V
-0.2
-0.4
-0.6
VIN = 8.4V
VIN = 10V
VIN = 12V
VIN = 13.2V
1
10
100
1000
10000
0.0001
0.001
0.01
0.1
1
10
Output Current (A)
Output Current (A)
Line Regulation
(VOUT = 5V)
Line Regulation
(VOUT = 3.3V)
0.4
0.3
0.2
0.1
0
0.05
0.04
0.03
0.02
0.01
0
1.5A
1mA
10mA
100mA
-0.1
-0.2
-0.3
-0.4
-0.01
-0.02
-0.03
-0.04
1.5A
1mA
10mA
100mA
6
7
8
9
10
11
12
5
6
7
8
9
10
11
12
Input Voltage (V)
Input Voltage (V)
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DATA SHEET
AAT1162
12V, 1.5A Step-Down DC/DC Converter
Typical Characteristics
Test circuit of Figure 2, unless otherwise specified.
Supply Current vs. Input Voltage
(VOUT = 5V)
Switching Current vs. Temperature
(VOUT = 5V)
170
160
150
140
170
160
150
140
130
130
85°C
VIN = 12V
VIN = 6V
120
120
110
25°C
-40°C
110
6
7
8
9
10
11
12
-40
-15
10
35
60
85
Input Voltage (V)
Temperature (°C)
N-Channel RDS(ON) vs. Temperature
P-Channel RDS(ON) vs. Temperature
(VIN = 6V)
120
100
80
60
40
20
0
200
180
160
140
120
100
80
60
40
VIN = 12V
VIN = 6V
VIN = 6V
VIN = 12V
20
0
-40
-15
10
35
60
85
-40
-15
10
35
60
85
Temperature (°C)
Temperature (°C)
Switching Frequency vs. Temperature
Start-up Time
(VOUT = 5.0V; CFF = 100pF; RLOAD = 1.5A;
CIN = 10µF; COUT = 22µF; L = 3.8µH)
810
805
800
795
790
785
780
775
770
6
5
4
3
2
1
0
6
5
4
3
2
1
0
VEN
V
OUT
ILOAD
VIN = 6V
VIN = 12V
-40
-15
10
35
60
85
Temperature (°C)
Time (500µs/div)
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DATA SHEET
AAT1162
12V, 1.5A Step-Down DC/DC Converter
Typical Characteristics
Test circuit of Figure 2, unless otherwise specified.
Line Transient
(VOUT = 5.0V; CFF = 100pF; VIN = 7.6V to 11V;
IOUT = 1.5A; CIN = 10µF; COUT = 22µF; L = 3.8µH)
Load Transient
(VOUT = 3.3V; CFF = 100pF; COUT = 66µF)
3.6
3.4
3.2
12
11
10
9
5.30
5.25
5.20
5.15
5.10
5.05
5.00
4.95
4.90
3
1.5A
2.8
8
10mA
2.6
2.4
2.2
2
7
6
5
4
Time (100µs/div)
Time (50µs/div)
Load Transient
(VOUT = 3.3V; COUT = 66µF; No CFF
Load Transient
(VOUT = 5V; CFF = 100pF; COUT = 66µF)
)
3.6
3.4
3.2
3
5.4
5.1
4.8
4.5
4.2
3.9
3.6
3.3
3
1.5A
1.5A
2.8
2.6
2.4
2.2
2
10mA
10mA
Time (50µs/div)
Time (50µs/div)
Load Transient
(VOUT = 5V; COUT = 66µF; No CFF
VOUT vs. Temperature
(VOUT = 3.3V; ILOAD = 1.5A)
)
5.4
5.1
4.8
4.5
4.2
3.9
3.6
3.3
3
1
0.8
0.6
0.4
0.2
0
1.5A
10mA
-0.2
-0.4
-0.6
-0.8
-40 -30 -20 -10
0
10 20 30 40 50 60 70 80 90
Time (50µs/div)
Temperature (°C)
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DATA SHEET
AAT1162
12V, 1.5A Step-Down DC/DC Converter
Typical Characteristics
Test circuit of Figure 2, unless otherwise specified.
Load Transient
(VOUT = 3.3V; CFF = 100pF; COUT = 22µF)
Load Transient
(VOUT = 3.3V; COUT = 22µF; No CFF)
3.9
3.6
3.3
3.7
3.3
2.9
2.5
2.1
1.7
1.3
0.9
0.5
3
1.5A
1.5A
2.7
2.4
2.1
1.8
1.5
10mA
10mA
Time (50µs/div)
Time (50µs/div)
Load Transient
(VOUT = 5V; CFF = 100pF; COUT = 22µF)
Load Transient
(VOUT = 5V; COUT = 22µF; No CFF)
5.4
5.4
5.1
4.8
4.5
4.2
3.9
3.6
3.3
3
5.1
4.8
4.5
4.2
3.9
3.6
3.3
3
1.5A
1.5A
10mA
10mA
Time (50µs/div)
Time (50µs/div)
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DATA SHEET
AAT1162
12V, 1.5A Step-Down DC/DC Converter
Functional Block Diagram
LDO
AIN
IN
Note1
FB
LDO
Current
Sense Amp
+
-
+
-
+
Error
Amp
Control
Logic
Current
Mode
-
LX
Comparator
Reference
PGND
AGND
EN
DGND
COMP
.
Note1: For fixed output voltage versions, FB is connected to the
error amplifier through the resistive voltage divider shown.
back for improved short-circuit performance, and ther-
mal overload protection to prevent damage in the event
of an external fault condition.
Functional Description
The AAT1162 is a current-mode step-down DC/DC con-
verter that operates over a wide 4V to 13.2V input volt-
age range and is capable of supplying up to 1.5A to the
load with the output voltage regulated as low as 0.6V.
Both the P-channel power switch and N-channel syn-
chronous rectifier are internal, reducing the number of
external components required. The output voltage is
adjusted by an external resistor divider; fixed output
voltage versions are available upon request. The regula-
tion system is externally compensated, allowing the cir-
cuit to be optimized for each application. The AAT1162
includes cycle-by-cycle current limiting, frequency fold-
Control Loop
The AAT1162 regulates the output voltage using con-
stant frequency current mode control. The AAT1162
monitors current through the high-side P-channel
MOSFET and uses that signal to regulate the output volt-
age. This provides improved transient response and
eases compensation. Internal slope compensation is
included to ensure the current “inside loop” stability.
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DATA SHEET
AAT1162
12V, 1.5A Step-Down DC/DC Converter
High efficiency is maintained under light load conditions
by automatically switching to variable frequency Light
Load control. In this condition, transition losses are
reduced by operating at a lower frequency at light
loads.
Applications Information
Setting the Output Voltage
Figure 1 shows the basic application circuit for the
AAT1162 and output setting resistors. Resistors R1 and
R2 program the output to regulate at a voltage higher
than 0.6V. To limit the bias current required for the
external feedback resistor string while maintaining good
noise immunity, the minimum suggested value for R2 is
5.9kΩ. Although a larger value will further reduce quies-
cent current, it will also increase the impedance of the
feedback node, making it more sensitive to external
noise and interference. Table 1 summarizes the resistor
values for various output voltages with R2 set to either
5.9kΩ for good noise immunity or 59kΩ for reduced no
load input current.
Short-Circuit Protection
The AAT1162 uses a cycle-by-cycle current limit to pro-
tect itself and the load from an external fault condition.
When the inductor current reaches the internally set
3.0A current limit, the P-channel MOSFET switch turns
off and the N-channel synchronous rectifier is turned on,
limiting the inductor and the load current.
During an overload condition, when the output voltage
drops below 50% of the regulation voltage (0.3V at FB),
the AAT1162 switching frequency drops by a factor of 4.
This gives the inductor current ample time to reset dur-
ing the off time to prevent the inductor current from
rising uncontrolled in a short-circuit condition.
L1
EP2
VOUT
VIN 4.5V- 13.2V
R4
C6
10μF
3.8μH
5V, 1.5A
LX
3
4
1
2
LX
LX
EN
IN
C1
100pF
R3
10Ω
5
7
C3
22μF
Thermal Protection
C2
0.1μF
432kΩ
IN
9
AAT1162
FB
AIN
10
11
C8
1μF
R6
COMP
AGND
The AAT1162 includes thermal protection that disables
the regulator when the die temperature reaches 140ºC.
It automatically restarts when the temperature decreas-
es by 25ºC or more.
59kΩ
6
13
16
R5
24kΩ
DGND
DGND
PGND
14
8
DGND
LDO
DGND
EP1
C7
330pF
C9
1μF
Figure 1: Typical Application Circuit.
The adjustable feedback resistors, combined with an
external feed forward capacitor (C1 in Figure 1), deliver
enhanced transient response for extreme pulsed load
applications. The addition of the feed forward capacitor
typically requires a larger output capacitor C3 for stabil-
ity. Larger C1 values reduce overshoot and undershoot
during startup and load changes. However, do not
exceed 470pF to maintain stable operation.
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DATA SHEET
AAT1162
12V, 1.5A Step-Down DC/DC Converter
The external resistors set the output voltage according
to the following equation:
Where ∆IL is inductor ripple current. Large value induc-
tors lower ripple current and small value inductors result
in high ripple currents. Choose inductor ripple current
approximately 32% of the maximum load current 1.5A,
or ∆IL = 480mA. For output voltages above 3.3V, the
minimum recommended inductor is 3.8μH. For 3.3V and
below, use a 2 to 3.8μH inductor. For optimum voltage-
positioning load transients, choose an inductor with DC
series resistance in the 15mꢀ to 20mꢀ range. For
higher efficiency at heavy loads (above 1A), or minimal
load regulation (but some transient overshoot), the
resistance should be kept below 18mꢀ. The DC current
rating of the inductor should be at least equal to the
maximum load current plus half the ripple current to
prevent core saturation (1.5A + 280mA). Table 2 lists
some typical surface mount inductors that meet target
applications for the AAT1162.
⎛
R1⎞
R2⎠
V
OUT = 0.6V 1 +
⎝
or
V
⎛
⎝
⎞
-1 · R2
⎠
OUT
R1 =
V
REF
Table 1 shows the resistor selection for different output
voltage settings.
R2 = 5.9(kΩ)
R1 (kΩ)
R2 = 59(kΩ)
R1 (kΩ)
VOUT (V)
0.8
0.9
1.0
1.1
1.2
1.3
1.4
1.5
1.8
1.85
2.0
2.5
3.3
5.0
1.96
2.94
3.92
4.99
5.90
6.81
7.87
8.87
11.8
12.4
13.7
18.7
26.7
43.2
19.6
29.4
39.2
49.9
59.0
68.1
78.7
88.7
118
124
137
187
267
Manufacturer’s specifications list both the inductor DC
current rating, which is a thermal limitation, and the
peak current rating, which is determined by the satura-
tion characteristics. The inductor should not show any
appreciable saturation under normal load conditions.
Some inductors may meet the peak and average current
ratings yet result in excessive losses due to a high DCR.
Always consider the losses associated with the DCR and
its effect on the total converter efficiency when selecting
an inductor. For example, the 4.7ꢁH WE-TPC series
inductor selected from Wurth has an 38mΩ DCR and a
2.4ADC current rating. At full load, the inductor DC loss
is 85mW which gives only a 1.1% loss in efficiency for a
1.5A, 5V output.
432
Table 1: Resistor Selection for Different Output
Voltage Settings. Standard 1% Resistors are
Substituted for Calculated Values.
Input Capacitor Selection
The input capacitor reduces the surge current drawn
from the input and switching noise from the device. The
input capacitor impedance at the switching frequency
shall be less than the input source impedance to prevent
high frequency switching current passing to the input. A
low ESR input capacitor sized for maximum RMS current
must be used. Ceramic capacitors with X5R or X7R
dielectrics are highly recommended because of their low
ESR and small temperature coefficients. A 10μF ceramic
capacitor is sufficient for most applications.
Inductor Selection
For most designs, the AAT1162 operates with inductors
of 2μH to 4.7μH. Low inductance values are physically
smaller, but require faster switching, which results in
some efficiency loss. The inductor value can be derived
from the following equation:
VOUT
L1 =
· 3.8µH
3.3
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DATA SHEET
AAT1162
12V, 1.5A Step-Down DC/DC Converter
Max DCR
(mΩ)
Rated DC
Current (A)
Size WxLxH
(mm)
Manufacturer
Part Number
L (μH)
Sumida
Sumida
Coilcraft
CDRH103RNP-2R2N
CDR7D43MNNP-3R7NC
MSS1038-382NL
DR73-4R7-R
2.2
3.7
3.8
4.7
4.7
16.9
18.9
13
29.7
38
5.10
4.3
4.25
3.09
2.40
10.3x10.5x3.1
7.6x7.6x4.5
10.2x7.7x3.8
6.0x7.6x3.55
5.8x5.8x2.8
Cooper Bussman
Wurth
7440530047
Table 2: Typical Surface Mount Inductors.
To estimate the required input capacitor size, determine
the acceptable input ripple level (VPP) and solve for C.
The calculated value varies with input voltage and is a
maximum when VIN is double the output voltage.
IO
2
IRMS(MAX)
=
VO
⎛
VO
1 -
⎞
⎠
·
VIN
⎝
VIN
The term
appears in both the input voltage
ripple and input capacitor RMS current equations and is
at maximum when VO is twice VIN. This is why the input
voltage ripple and the input capacitor RMS current ripple
are a maximum at 50% duty cycle. The input capacitor
provides a low impedance loop for the edges of pulsed
current drawn by the AAT1162. Low ESR/ESL X7R and
X5R ceramic capacitors are ideal for this function. To
minimize stray inductance, the capacitor should be
placed as closely as possible to the IC. This keeps the
high frequency content of the input current localized,
minimizing EMI and input voltage ripple. The proper
placement of the input capacitor (C6) can be seen in the
evaluation board layout in Figure 3. Additional noise fil-
tering for proper operation is accomplished by adding a
small 0.1μF capacitor on the IN pins (C2).
VO
⎛
VO ⎞
VIN ⎠
· 1 -
⎝
VIN
CIN =
⎛ VPP
⎝ IO
⎞
⎠
- ESR ·FOSC
VO
⎛
VO ⎞
VIN ⎠
1
· 1 -
⎝
=
for VIN = 2 · VO
VIN
4
1
CIN(MIN)
=
⎛ VPP
⎝ IO
⎞
⎠
- ESR · 4 · FOSC
Always examine the ceramic capacitor DC voltage coef-
ficient characteristics when selecting the proper value.
For example, the capacitance of a 10ꢁF, 16V, X5R ceram-
ic capacitor with 12V DC applied is actually about 8.5ꢁF.
A laboratory test set-up typically consists of two long
wires running from the bench power supply to the eval-
uation board input voltage pins. The inductance of these
wires, along with the low-ESR ceramic input capacitor,
can create a high Q network that may affect converter
performance. This problem often becomes apparent in
the form of excessive ringing in the output voltage dur-
ing load transients. Errors in the loop phase and gain
measurements can also result. Since the inductance of a
short PCB trace feeding the input voltage is significantly
lower than the power leads from the bench power sup-
ply, most applications do not exhibit this problem. In
applications where the input power source lead induc-
tance cannot be reduced to a level that does not affect
the converter performance, a high ESR tantalum or alu-
minum electrolytic should be placed in parallel with the
low ESR, ESL bypass ceramic. This dampens the high Q
network and stabilizes the system.
The maximum input capacitor RMS current is:
VO
⎛
VO ⎞
VIN ⎠
IRMS = IO ·
· 1 -
⎝
VIN
The input capacitor RMS ripple current varies with the
input and output voltage and will always be less than or
equal to half of the total DC load current:
VO
⎛
VO ⎞
VIN ⎠
1
· 1 -
⎝
=
D · (1 - D) = 0.52 =
VIN
2
for VIN = 2 · VO
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DATA SHEET
AAT1162
12V, 1.5A Step-Down DC/DC Converter
The maximum output capacitor RMS ripple current is
given by:
Output Capacitor Selection
The output capacitor is required to keep the output volt-
age ripple small and to ensure regulation loop stability.
The output capacitor must have low impedance at the
switching frequency. Ceramic capacitors with X5R or
X7R dielectrics are recommended due to their low ESR
and high ripple current. The output ripple VOUT is deter-
mined by:
1
V
OUT · (VIN(MAX) - VOUT
)
IRMS(MAX)
=
·
L · FOSC · VIN(MAX)
2 · 3
Dissipation due to the RMS current in the ceramic output
capacitor ESR is typically minimal, resulting in less than
a few degrees rise in hot-spot temperature.
VOUT · (VIN - VOUT
)
⎛
1
⎞
ΔVOUT
≤
· ESR +
Compensation
VIN · FOSC · L
⎝
8 · FOSC · COUT
⎠
The AAT1162 step-down converter uses peak current
mode control with slope compensation scheme to main-
tain stability with lower value inductors for duty cycles
greater than 50%. The regulation feedback loop in the
IC is stabilized by the components connected to the
COMP pin, as shown in Figure 1.
The output capacitor limits the output ripple and pro-
vides holdup during large load transitions. A 10ꢁF to
47ꢁF X5R or X7R ceramic capacitor typically provides
sufficient bulk capacitance to stabilize the output during
large load transitions and has the ESR and ESL charac-
teristics necessary for low output ripple. The output volt-
age droop due to a load transient is dominated by the
capacitance of the ceramic output capacitor. During a
step increase in load current, the ceramic output capac-
itor alone supplies the load current until the loop
responds. Within two or three switching cycles, the loop
responds and the inductor current increases to match
the load current demand. The relationship of the output
voltage droop during the three switching cycles to the
output capacitance can be estimated by:
To optimize the compensation components, the following
equations can be used. The compensation resistor RCOMP
(R5) is calculated using the following equation:
2πVOUT · COUT
10GEA · GCOMP · VFB
·
FOSC
RCOMP (R5)=
Where VFB = 0.6V, GCOMP = 40.1734 and GEA = 9.091 ·
10-5.
FOSC is the switching frequency and COUT is based on the
output capacitor calculation. The CCOMP value can be
determined from the following equation:
3 · ΔILOAD
DROOP · FOSC
COUT
=
V
4
Once the average inductor current increases to the DC
load level, the output voltage recovers. The above equa-
tion establishes a limit on the minimum value for the
output capacitor with respect to load transients. The
internal voltage loop compensation also limits the mini-
mum output capacitor value to 22ꢁF. This is due to its
effect on the loop crossover frequency (bandwidth),
phase margin, and gain margin. Increased output capac-
itance will reduce the crossover frequency with greater
phase margin.
CCOMP (C7) =
⎛FOSC
⎞
2πRCOMP (R5) ·
⎝ 10 ⎠
The feed forward capacitor CFF (C1) provides faster
transient response for pulsed load applications. The
addition of the feed forward capacitor typically requires
a larger output capacitor C1 for stability. Larger C1 val-
ues reduce overshoot and undershoot during startup
and line/load changes. The CFF value can be from 100pF
to 470pF, but do not exceed 470pF to maintain stable
operation.
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DATA SHEET
AAT1162
12V, 1.5A Step-Down DC/DC Converter
4. The input capacitors (C9 and C1) should be con-
nected as close as possible to IN (Pins 4 and 5) and
DGND (Pin 6) to get good power filtering.
5. Keep the switching node LX away from the sensitive
FB node.
6. The feedback trace for the FB pin should be separate
from any power trace and connected as closely as
possible to the load point. Sensing along a high-
current load trace will degrade DC load regulation.
The feedback resistors should be placed as close as
possible to the FB pin (Pin 9) to minimize the length
of the high impedance feedback trace.
7. The output capacitors C3, 4, and 5 and L1 should be
connected as close as possible and there should not
be any signal lines under the inductor.
Layout Guidance
Figure 2 is the schematic for the evaluation board. When
laying out the PC board, the following layout guideline
should be followed to ensure proper operation of the
AAT1162:
1. Exposed pad EP1 must be reliably soldered to PGND/
DGND/AGND. The exposed thermal pad should be
connected to board ground plane and pins 6, 11, 13,
14 and 16. The ground plane should include a large
exposed copper pad under the package for thermal
dissipation.
2. The power traces, including GND traces, the LX
traces and the VIN trace should be kept short, direct
and wide to allow large current flow. The L1 connec-
tion to the LX pins should be as short as possible.
Use several via pads when routing between layers.
3. Exposed pad pin EP2 must be reliably soldered to the
LX pins 1 and 2. The exposed thermal pad should be
connected to the board LX connection and the induc-
tor L1 and also pins 1 and 2. The LX plane should
include a large exposed copper pad under the pack-
age for thermal dissipation.
8. The resistance of the trace from the load return to
the PGND (Pin 16) should be kept to a minimum.
This will help to minimize any error in DC regulation
due to differences in the potential of the internal
signal ground and the power ground.
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DATA SHEET
AAT1162
12V, 1.5A Step-Down DC/DC Converter
JP1
Enable
TP1
GND
TP14
GND
R1
4.75K
R2
4.75K
TP2
LX
TP3
Enable
U1
VOUT
TP4
L1
3.8μH
VIN
15
1
TP5
EN
IN
LX
LX
FB
4
5
3
2
C1
VOUT
TP6
AAT1162
R3
9
10
100pF
VIN
TP7
IN
C2
0.1μF
432K
R4
N/C
COMP
10Ω
7
11
12
VOUT
TB2
R5
C3
22μF
C4
NP
C5
NP
AIN
AGND
N/C
VIN
24K
6
13
R6
DGND
DGND
C6
10μF
TB1
VIN
14
8
59K
DGND
LDO
16
C7
330pF
PGND
VOUT
TP8
C8
1μF
C9
1μF
TP9
*
TP11
GND
GND
TP12
GND
TP13
GND
GND
DGND
*Note: Connect GND, DGND, and AGND at IC EP1
Figure 2: AAT1162 Evaluation Board Schematic.
Figure 3: AAT1162 Evaluation Board
Component Side Layout.
Figure 4: AAT1162 Evaluation Board
Solder Side Layout.
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DATA SHEET
AAT1162
12V, 1.5A Step-Down DC/DC Converter
Design Example
Specifications
VOUT
VIN
5V @ 1.5A, Pulsed Load ILOAD = 1.5A
12V nominal
FOSC
TAMB
800kHz
85°C in TDFN34-16 Package
Output Inductor
VOUT
L =
· 3.8µH = 5.75µH; use 4.7µH (see Table 2)
3.3
ΔIL = 0.32 · ILOAD = 480mA
For Cooper Bussman inductor DR73-4R7-R 4.7μH DCR = 29.7mW max.
⎛
⎞
⎠
VOUT
VO1
5
V
5V
⎛
⎞
⎠
ΔI1 =
⋅ 1 -
⎝
=
⋅ 1 -
= 480mA
⎝
L1 ⋅ FOSC
VIN
4.7µH ⋅ 800kHz
12V
ΔI1
2
IPK1 = ILOAD
+
= 1.5A + 0.480A = 1.98A
2
PL1 = ILOAD ⋅ DCR = 3A2 ⋅ 13mΩ = 117mW
Output Capacitor
VDROOP = 0.2V
3 · ΔILOAD
VDROOP · FOSC
3 · 1.5A
COUT
=
=
= 28µF; use 22µF
0.2V · 800kHz
(VOUT) · (VIN(MAX) - VOUT
)
1
5V · (12V - 5V)
1
·
= 139mArms
IRMS(MAX)
=
·
=
4.7µH · 800kHz · 12V
L · FOSC · VIN(MAX)
2· 3
2· 3
Pesr = esr · IRMS2 = 5mΩ · (277mA)2 = 384µW
Input Capacitor
Input Ripple VPP = 50mV
1
1
CIN =
=
= 11µF; use 10µF
⎛ VPP
⎝ ILOAD
⎞
⎛ 50mV
⎝ 1.5A
⎞
⎠
- ESR · 4 · FOSC
- 5mΩ · 4 · 800kHz
⎠
ILOAD
IRMS(MAX)
=
= 0.75Arms
2
P = esr · IRMS2 = 5mΩ · (0.75A)2 = 2.81mW
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DATA SHEET
AAT1162
12V, 1.5A Step-Down DC/DC Converter
AAT1162 Losses
Total losses can be estimated by calculating the dropout (VIN = VO) losses where the power MOSFET RDS(ON) will be at
the maximum value. All values assume an 85°C ambient temperature and a 140°C junction temperature with the TDFN
37°C/W package.
PLOSS = ILOAD2 · RDS(ON)H = 1.5A2 · 0.158Ω = 0.355W
TJ(MAX) = TAMB + ΘJA · PLOSS = 85°C + (37°C/W) · 355mW = 96.6°C
The total losses are also investigated at the nominal input voltage (12V). The simplified version of the RDS(ON) losses
assumes that the N-channel and P-channel RDS(ON) are equal.
PTOTAL = ILOAD2 · RDS(ON) + [(tsw · FOSC · ILOAD + IQ) · VIN]
= 1.5A2 · 100mΩ + [(5ns · 800kHz · 1.5A + 150µA) · 12V] = 299mW
TJ(MAX) = TAMB + ΘJA · PLOSS = 85°C + (37°C/W) · 299mW = 96°C
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DATA SHEET
AAT1162
12V, 1.5A Step-Down DC/DC Converter
Ordering Information
Package
Marking1
Part Number (Tape and Reel)2
AAT1162IRN-0.6-T1
TDFN34-16
YYXYY
Skyworks Green™ products are compliant with
all applicable legislation and are halogen-free.
For additional information, refer to Skyworks
Definition of Green™, document number
SQ04-0074.
Package Information
TDFN34-163
1.600 0.050
R0.15 (REF)
Pin 1 ID
3.000 0.050
Index Area
0.25 REF
0.430 0.050
1.600 0.050
Top View
Bottom View
+ 0.100
-0.000
0
0.230 0.050
Side View
All dimensions in millimeters.
1. XYY = assembly and date code.
2. Sample stock is generally held on part numbers listed in BOLD.
3. The leadless package family, which includes QFN, TQFN, DFN, TDFN and STDFN, has exposed copper (unplated) at the end of the lead terminals due to the manufacturing
process. A solder fillet at the exposed copper edge cannot be guaranteed and is not required to ensure a proper bottom solder connection.
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DATA SHEET
AAT1162
12V, 1.5A Step-Down DC/DC Converter
Copyright © 2012, 2013 Skyworks Solutions, Inc. All Rights Reserved.
Information in this document is provided in connection with Skyworks Solutions, Inc. (“Skyworks”) products or services. These materials, including the information contained herein, are provided by Skyworks as a
service to its customers and may be used for informational purposes only by the customer. Skyworks assumes no responsibility for errors or omissions in these materials or the information contained herein. Sky-
works may change its documentation, products, services, specifications or product descriptions at any time, without notice. Skyworks makes no commitment to update the materials or information and shall have no
responsibility whatsoever for conflicts, incompatibilities, or other difficulties arising from any future changes.
No license, whether express, implied, by estoppel or otherwise, is granted to any intellectual property rights by this document. Skyworks assumes no liability for any materials, products or information provided here-
under, including the sale, distribution, reproduction or use of Skyworks products, information or materials, except as may be provided in Skyworks Terms and Conditions of Sale.
THE MATERIALS, PRODUCTS AND INFORMATION ARE PROVIDED “AS IS” WITHOUT WARRANTY OF ANY KIND, WHETHER EXPRESS, IMPLIED, STATUTORY, OR OTHERWISE, INCLUDING FITNESS FOR A PARTICULAR
PURPOSE OR USE, MERCHANTABILITY, PERFORMANCE, QUALITY OR NON-INFRINGEMENT OF ANY INTELLECTUAL PROPERTY RIGHT; ALL SUCH WARRANTIES ARE HEREBY EXPRESSLY DISCLAIMED. SKYWORKS DOES
NOT WARRANT THE ACCURACY OR COMPLETENESS OF THE INFORMATION, TEXT, GRAPHICS OR OTHER ITEMS CONTAINED WITHIN THESE MATERIALS. SKYWORKS SHALL NOT BE LIABLE FOR ANY DAMAGES, IN-
CLUDING BUT NOT LIMITED TO ANY SPECIAL, INDIRECT, INCIDENTAL, STATUTORY, OR CONSEQUENTIAL DAMAGES, INCLUDING WITHOUT LIMITATION, LOST REVENUES OR LOST PROFITS THAT MAY RESULT FROM
THE USE OF THE MATERIALS OR INFORMATION, WHETHER OR NOT THE RECIPIENT OF MATERIALS HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
Skyworks products are not intended for use in medical, lifesaving or life-sustaining applications, or other equipment in which the failure of the Skyworks products could lead to personal injury, death, physical or en-
vironmental damage. Skyworks customers using or selling Skyworks products for use in such applications do so at their own risk and agree to fully indemnify Skyworks for any damages resulting from such improper
use or sale.
Customers are responsible for their products and applications using Skyworks products, which may deviate from published specifications as a result of design defects, errors, or operation of products outside of pub-
lished parameters or design specifications. Customers should include design and operating safeguards to minimize these and other risks. Skyworks assumes no liability for applications assistance, customer product
design, or damage to any equipment resulting from the use of Skyworks products outside of stated published specifications or parameters.
Skyworks, the Skyworks symbol, and “Breakthrough Simplicity” are trademarks or registered trademarks of Skyworks Solutions, Inc., in the United States and other countries. Third-party brands and names are for
identification purposes only, and are the property of their respective owners. Additional information, including relevant terms and conditions, posted at www.skyworksinc.com, are incorporated by reference.
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