AAT2515IWP-AA-T1 [SKYWORKS]
Dual 600mA, Fast Transient High Frequency Buck Converter; 两个600mA ，快速瞬态高频降压转换器
| 型号： | AAT2515IWP-AA-T1 |
| 厂家： | 
SKYWORKS SOLUTIONS INC. |
| 描述： | Dual 600mA, Fast Transient High Frequency Buck Converter |
| 文件： | 总20页 (文件大小：1580K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
DATA SHEET
AAT2515
Dual 600mA, FastTransient High Frequency Buck Converter
Features
General Description
The AAT2515 is a dual channel synchronous buck con-
verter operating with an input voltage range of 2.7V to
5.5V, making it ideal for applications with single-cell
lithium-ion/polymer batteries.
• VIN Range: 2.7V to 5.5V
• Output Current:
Channel 1: 600mA
Channel 2: 600mA
• 98% Efficient Step-Down Converter
• Integrated Power Switches
• 100% Duty Cycle
▪
▪
Both regulators have independent input and enable pins.
Offered with fixed or adjustable output voltages, each
channel is designed to operate with 27μA (typical) of
quiescent current, allowing for high efficiency under light
load conditions.
• 1.4MHz Switching Frequency
• Internal Soft Start
• 150μs Typical Turn-On Time
• Over-Temperature Protection
• Current Limit Protection
• TDFN33-12 Package
The AAT2515 requires only three external components
(CIN, COUT, and LX) for each converter, minimizing cost and
real estate. Both channels are designed to deliver 600mA
of load current and operate with a switching frequency of
1.4MHz, reducing the size of external components.
• -40°C to +85°C Temperature Range
The AAT2515 is available in a Pb-free, 12-pin TDFN33
package and is rated over the -40°C to +85°C tempera-
ture range.
Applications
• Cellular Phones
• Digital Cameras
• Handheld Instruments
• Microprocessor / DSP Core / IO Power
• PDAs and Handheld Computers
Typical Application
VOUT1
VIN1
LX1
L1
4.7μH
VIN2
EN1
FB1
CIN
10μF
VBAT
VOUT2
AAT2515
LX2
FB2
L2
4.7μH
COUT
10μF
EN2
10μF
GND
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DATA SHEET
AAT2515
Dual 600mA, FastTransient High Frequency Buck Converter
Pin Descriptions
Pin #
Symbol Function
Enable pin for Channel 1. Active high. When connected low, it disables the channel and consumes less
than 1μA of current.
1
EN1
Feedback input pin for Channel 1. This pin is connected to the converter output. It is used to see the
output of the converter to regulate to the desired value via an external resistor divider.
Ground.
Enable pin for Channel 2. Active high. When connected low, it disables the channel and consumes less
than 1μA of current.
2
3, 6, 7, 10
4
FB1
GND
EN2
Feedback input pin for Channel 2. This pin is connected to the converter output. It is used to see the
output of the converter to regulate to the desired value via an external resistor divider.
5
FB2
8
9
11
12
LX2
VIN2
LX1
Power switching node for Channel 2. Output switching node that connects to the output inductor.
Input supply voltage for Channel 2. Must be closely decoupled.
Power switching node for Channel 2. Output switching node that connects to the output inductor.
Input supply voltage for Channel 1. Must be closely decoupled.
VIN1
Pin Configuration
TDFN33-12
(Top View)
1
2
3
4
5
6
12
11
10
9
EN1
FB1
VIN1
LX1
GND
EN2
FB2
GND
VIN2
LX2
8
7
GND
GND
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DATA SHEET
AAT2515
Dual 600mA, FastTransient High Frequency Buck Converter
Absolute Maximum Ratings1
Symbol
Description
Value
Units
VIN
VLX
VFB
VEN
TJ
Input Voltages to GND
LX to GND
FB1 and FB2 to GND
EN1 and EN2 to GND
Operating Junction Temperature Range
Maximum Soldering Temperature (at leads, 10 sec)
6.0
V
V
V
V
°C
°C
-0.3 to VIN + 0.3
-0.3 to VIN + 0.3
-0.3 to 6.0
-40 to 150
300
TLEAD
Thermal Information
Symbol
Description
Value
Units
PD
JA
Maximum Power Dissipation
Thermal Resistance2
2.0
50
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. Mounted on an FR4 board.
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DATA SHEET
AAT2515
Dual 600mA, FastTransient High Frequency Buck Converter
Electrical Characteristics1
VIN = 3.6V; TA = -40°C to +85°C, unless otherwise noted. Typical values are TA = 25°C.
Symbol Description
Conditions
Min Typ Max Units
VIN
VOUT
VOUT
Input Voltage
2.7
-3.0
0.6
5.5
3.0
VIN
V
%
V
μA
μA
μA
μA
A
%
MHz
Output Voltage Tolerance
Output Voltage Range
Quiescent Current
Shutdown Current
LX Leakage Current
Feedback Leakage
P-Channel Current Limit
High Side Switch On Resistance
Low Side Switch On Resistance
Line Regulation
IOUT = 0 to 600mA; VIN = 2.7V to 5.5V
IQ
Per Channel
27
70
ISHDN
ILX_LEAK
IFB
EN1 = EN2 = GND
VIN = 5.5V, VLX = 0 to VIN
VFB = 1.0V
1.0
1.0
0.2
ILIM
Both Channels
1.2
0.45
0.40
0.2
RDS(ON)H
RDS(ON)L
VLINE
FOSC
VIN = 2.7V to 5.5V
Oscillator Frequency
1.4
From Enable to Output Regulation; Both
Channels
TS
Start-Up Time
150
μs
TSD
THYS
VEN(L)
VEN(H)
IEN
Over-Temperature Shutdown Threshold
Over-Temperature Shutdown Hysteresis
Enable Threshold Low
Enable Threshold High
Input Low Current
140
15
°C
°C
V
V
μA
0.6
1.0
1.4
-1.0
VIN = VFB = 5.5V
1. The AAT2515 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
AAT2515
Dual 600mA, FastTransient High Frequency Buck Converter
Typical Characteristics
EN1 = VIN; EN2 = GND.
Efficiency vs. Load
(VOUT = 1.8V; L = 4.7μH)
DC Regulation
(VOUT = 1.8V)
100
1.0
VIN = 2.7V
90
0.5
VIN = 4.2V
VIN = 4.2V
80
VIN = 3.6V
0.0
70
60
50
VIN = 3.6V
-0.5
VIN = 2.7V
-1.0
0.1
0.1
0.1
1
1
1
10
100
1000
1000
1000
0.1
1
10
100
1000
Output Current (mA)
Output Current (mA)
Efficiency vs. Load
(VOUT = 2.5V; L = 6.8μH)
DC Regulation
(VOUT = 2.5V)
100
90
80
70
60
50
1.0
0.5
VIN = 2.7V
VIN = 4.2V
VIN = 5.0V
VIN = 5.0V
VIN = 4.2V
0.0
VIN = 3.6V
VIN = 3.6V
-0.5
-1.0
VIN = 3.0V
10
100
0.1
1
10
100
1000
Output Current (mA)
Output Current (mA)
Efficiency vs. Load
(VOUT = 3.3V; L = 6.8μH)
DC Regulation
(VOUT = 3.3V; L = 6.8µH)
100
1.0
0.5
VIN = 3.6V
VIN = 5.0V
VIN = 4.2V
90
80
70
60
50
VIN = 4.2V
0.0
VIN = 5.0V
-0.5
-1.0
VIN = 3.6V
10
100
0.1
1
10
100
1000
Output Current (mA)
Output Current (mA)
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DATA SHEET
AAT2515
Dual 600mA, FastTransient High Frequency Buck Converter
Typical Characteristics
EN1 = VIN; EN2 = GND.
Soft Start
(VIN = 3.6V; VOUT = 1.8V; IOUT = 400mA)
Line Regulation
(VOUT = 1.8V)
0.40
0.30
0.20
0.10
0.00
-0.10
-0.20
-0.30
-0.40
5.0
4.0
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
-0.2
-0.4
VEN
VO
IOUT = 10mA
3.0
2.0
1.0
0.0
-1.0
-2.0
-3.0
-4.0
-5.0
IOUT = 1mA
IOUT = 400mA
IL
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
Time (100μs/div)
Input Voltage (V)
Output Voltage Error vs. Temperature
(VIN = 3.6V; VO = 1.8V; IOUT = 400mA)
Switching Frequency vs. Temperature
(VIN = 3.6V; VOUT = 1.8V)
2.0
1.0
15.0
12.0
9.0
6.0
3.0
0.0
0.0
-3.0
-6.0
-9.0
-12.0
-15.0
-1.0
-2.0
-40
-20
0
20
40
60
80
100
-40
-20
0
20
40
60
80
100
Temperature (°C)
Temperature (°°C)
Frequency vs. Input Voltage
No Load Quiescent Current vs. Input Voltage
2.0
1.0
50
45
40
35
VOUT = 1.8V
0.0
25°C
85°C
-1.0
-2.0
-3.0
-4.0
30
25
20
15
10
VOUT = 2.5V
VOUT = 3.3V
-40°C
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
Input Voltage (V)
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DATA SHEET
AAT2515
Dual 600mA, FastTransient High Frequency Buck Converter
Typical Characteristics
EN1 = VIN; EN2 = GND.
P-Channel RDS(ON) vs. Input Voltage
N-Channel RDS(ON) vs. Input Voltage
750
700
650
600
550
500
450
400
350
300
750
700
650
600
550
500
450
400
350
300
120°C
100°C
120°C
100°C
85°C
85°C
25°C
25°C
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
Input Voltage (V)
Input Voltage (V)
Load Transient Response
(1mA to 300mA; VIN = 3.6V; VOUT = 1.8V;
C1 = 10μF; CFF = 100pF)
Load Transient Response
(300mA to 400mA; VIN = 3.6V;
VOUT = 1.8V; C1 = 4.7μF)
2.0
1.90
1.85
1.80
1.75
1.9
1.8
1.7
VO
VO
IO
IO
300mA
400mA
300mA
1mA
IL
0.4
0.3
0.2
0.1
IL
0
Time (50μs/div)
Time (50μs/div)
Load Transient Response
(300mA to 400mA; VIN = 3.6V;
VOUT = 1.8V; C1 = 10μF)
Load Transient Response
(300mA to 400mA; VIN = 3.6V; VOUT = 1.8V;
C1 = 10μμF; C4 = 100pF)
1.850
1.90
1.85
1.80
1.75
1.825
1.800
1.775
VO
IO
VO
IO
400mA
400mA
300mA
300mA
0.4
0.4
0.3
0.2
0.1
0.3
0.2
0.1
IL
IL
Time (50μs/div)
Time (50μs/div)
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DATA SHEET
AAT2515
Dual 600mA, FastTransient High Frequency Buck Converter
Typical Characteristics
EN1 = VIN; EN2 = GND.
Line Response
(VOUT = 1.8V @ 400mA)
Output Ripple
(VIN = 3.6V; VOUT = 1.8V; IOUT = 1mA)
40
20
0.30
0.25
0.20
0.15
0.10
0.05
0.00
-0.05
-0.10
1.82
1.81
1.80
1.79
1.78
1.77
6.0
5.5
5.0
4.5
4.0
3.5
3.0
VO
0
-20
-40
-60
-80
-100
-120
IL
1.76
Time (25μs/div)
Time (10µs/div)
Output Ripple
(VIN = 3.6V; VOUT = 1.8V; IOUT = 400mA)
40
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
20
VO
0
-20
-40
-60
-80
IL
-100
-120
Time (500ns/div)
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DATA SHEET
AAT2515
Dual 600mA, FastTransient High Frequency Buck Converter
Functional Block Diagram
FB1
VIN1
DH
DL
Comp.
Err.
Amp.
LX1
Logic
Voltage
Reference
Control
Logic
EN1
GND
VIN2
See
Note
GND
FB2
DH
DL
Comp.
Err.
Amp.
LX2
Logic
Voltage
Reference
Control
Logic
EN2
GND
See
Note
GND
Note: Internal resistor divider included for fixed output voltage versions. For low voltage versions, the feedback pin is tied directly to the error amplifier input.
The AAT2515 also features soft-start control to limit
Functional Description
inrush current. Soft start increases the inductor current
The AAT2515 is a high performance power management
limit point in discrete steps when power is applied to the
IC comprised of two buck converters. Each channel has
input or when the enable pins are pulled high. It limits
independent input voltages and enable pins. Designed to
the current surge seen at the input and eliminates out-
operate at 1.4MHz of switching frequency, the converters
put voltage overshoot. The enable input, when pulled
require only three external components (CIN, COUT, and
low, forces the converter into a low power, non-switching
LX), minimizing cost and size of external components.
state consuming less than 1μA of current.
Both converters are designed to operate with an input
For overload conditions, the peak input current is limit-
voltage range of 2.7V to 5.5V. Typical values of the out-
ed. As load impedance decreases and the output voltage
put filter are 4.7μH and 10μF ceramic capacitor. The
falls closer to zero, more power is dissipated internally,
output voltage operates to as low as 0.6V and is offered
raising the device temperature. Thermal protection com-
as both fixed and adjustable. Power devices are sized for
pletely disables switching when internal dissipation
600mA current capability while maintaining over 90%
becomes excessive, protecting the device from damage.
efficiency at full load. Light load efficiency is maintained
The junction over-temperature threshold is 140°C with
at greater than 80% down to 500μA of load current.
15°C of hysteresis. The under-voltage lockout guaran-
Both channels have excellent transient response, load,
tees sufficient VIN bias and proper operation of all inter-
and line regulation. Transient response time is typically
nal circuits prior to activation.
less than 20μs.
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DATA SHEET
AAT2515
Dual 600mA, FastTransient High Frequency Buck Converter
Input Capacitor
Applications Information
Select a 4.7μF to 10μF X7R or X5R ceramic capacitor for
the input. To estimate the required input capacitor size,
determine the acceptable input ripple level (VPP) and
solve for C. The calculated value varies with input volt-
age and is a maximum when VIN is double the output
voltage.
Inductor Selection
The step-down converter uses peak current mode con-
trol with slope compensation to maintain stability for
duty cycles greater than 50%. The output inductor value
must be selected so the inductor current down slope
meets the internal slope compensation requirements.
The internal slope compensation for the adjustable and
low-voltage fixed versions of the AAT2515 is 0.24A/μs.
This equates to a slope compensation that is 75% of the
inductor current down slope for a 1.5V output and 4.7μH
inductor.
VO
⎛
⎝
VO ⎞
VIN ⎠
⋅
1 -
VIN
CIN =
⎛ VPP
⎝ IO
⎞
- ESR
⋅
FS
⎠
This equation provides an estimate for the input capaci-
tor required for a single channel.
0.75 ⋅ VO 0.75 ⋅ 1.5V
= 0.24
A
m =
=
L
4.7µH
µs
Configuration
Output Voltage
Inductor
1V, 1.2V
1.5V, 1.8V
2.5V, 3.3V
0.6V to 3.3V
2.2μH
4.7μH
6.8μH
4.7μH
This is the internal slope compensation for the adjust-
able (0.6V) version or low-voltage fixed version. When
externally programming the 0.6V version to a 2.5V out-
put, the calculated inductance would be 7.5μH.
0.6V Adjustable With
External Feedback
Fixed Output
Table 1: Inductor Values.
0.75 ⋅ VO
m
0.75V
0.24A/µs
µs
L =
=
≈
3
⋅ VO
The equation below solves for input capacitor size for
both channels. It makes the worst-case assumptions
that both converters are operating at 50% duty cycle
and are synchronized.
A
µs
= 3
⋅ 2.5V = 7.5µH
A
In this case, a standard 6.8μH value is selected. For high-
voltage fixed versions (2.5V and above), m = 0.48A/μs.
Table 1 displays inductor values for the AAT2515 fixed
and adjustable options.
1
CIN =
⎛
VPP
⎞
⎠
- ESR · 4 · FS
⎝IO1 + IO2
Because the AAT2515 channels will generally operate at
different duty cycles and are not synchronized, the
actual ripple will vary and be less than the ripple (VPP)
used to solve for the input capacitor in the equation
above.
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.
Always examine the ceramic capacitor DC voltage coef-
ficient characteristics when selecting the proper value.
For example, the capacitance of a 10μF 6.3V X5R ceram-
ic capacitor with 5V DC applied is actually about 6μF.
The maximum input capacitor RMS current is:
The 4.7μH CDRH3D16 series inductor selected from
Sumida has a 105m DCR and a 900mA DC current rat-
ing. At full load, the inductor DC loss is 37.8mW which
gives a 4.2% loss in efficiency for a 600mA 1.5V output.
VO1
⎛
V ⎞
V
⎛
V ⎞
⎛
⎞
⎛
⎞
O1
O2
IRMS = IO1
·
· 1 -
⎝
+ IO2
·
O2 · 1 -
VIN
VIN
V ⎠
IN
⎝
V ⎠
IN
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DATA SHEET
AAT2515
Dual 600mA, FastTransient High Frequency Buck Converter
The input capacitor RMS ripple current varies with the
the power leads from the bench power supply, most
applications do not exhibit this problem.
input and output voltage and will always be less than or
equal to half of the total DC load current of both convert-
ers combined.
In applications where the input power source lead induc-
tance cannot be reduced to a level that does not affect
converter performance, a high ESR tantalum or alumi-
num electrolytic capacitor should be placed in parallel
with the low ESR, ESL bypass ceramic capacitor. This
dampens the high Q network and stabilizes the system.
IO1(MAX) + IO2(MAX)
IRMS(MAX)
=
2
This equation also makes the worst-case assumption
that both converters are operating at 50% duty cycle
and are synchronized. Since the converters are not syn-
chronized and are not both operating at 50% duty cycle,
the actual RMS current will always be less than this.
Losses associated with the input ceramic capacitor are
typically minimal.
Output Capacitor
The output capacitor limits the output ripple and pro-
vides holdup during large load transitions. A 10μF X5R
or X7R ceramic capacitor typically provides sufficient
bulk capacitance to stabilize the output during large load
transitions and has the ESR and ESL characteristics nec-
essary for low output ripple.
VO
⎛
VO
⎞
⎠
·
1 -
⎝
VIN
VIN
The term
appears in both the input voltage
ripple and input capacitor RMS current equations. It is
a 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 output voltage 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 capacitor alone supplies the load current
until the loop responds. As the loop responds, the induc-
tor current increases to match the load current demand.
This typically takes several switching cycles and can be
estimated by:
The input capacitor provides a low impedance loop for the
edges of pulsed current drawn by the AAT2515. Low ESR/
ESL X7R and X5R ceramic capacitors are ideal for this
function. To minimize the 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.
3 · ΔILOAD
=
COUT
VDROOP · FS
The proper placement of the input capacitor (C3 and C8)
can be seen in the evaluation board layout in Figure 2.
Since decoupling must be as close to the input pins as
possible, it is necessary to use two decoupling capaci-
tors. C3 provides the bulk capacitance required for both
converters, while C8 is a high frequency bypass capaci-
tor for the second channel (see C3 and C8 placement in
Figure 2).
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
minimum output capacitor value to 10μF. 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.
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.
The maximum output capacitor RMS ripple current is
given by:
This problem often becomes apparent in the form of
excessive ringing in the output voltage during load tran-
sients. Errors in the loop phase and gain measurements
can also result.
1
V
OUT · (VIN(MAX) - VOUT
)
IRMS(MAX)
=
·
L · F · 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.
Since the inductance of a short printed circuit board
trace feeding the input voltage is significantly lower than
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DATA SHEET
AAT2515
Dual 600mA, FastTransient High Frequency Buck Converter
Adjustable Output Resistor Selection
Thermal Calculations
For applications requiring an adjustable output voltage,
the 0.6V version can be programmed externally. Resistors
R1 through R4 of Table 2 program the output to regulate
at a voltage higher than 0.6V. To limit the bias current
required for the external feedback resistor string, the
minimum suggested value for R2 and R4 is 59k.
Although a larger value will reduce the quiescent cur-
rent, it will also increase the impedance of the feedback
node, making it more sensitive to external noise and
interference. Table 2 summarizes the resistor values for
various output voltages with R2 and R4 set to either
59k for good noise immunity or 221k for reduced no
load input current.
There are three types of losses associated with the
AAT2515 converter: switching losses, conduction losses,
and quiescent current losses. Conduction losses are
associated with the RDS(ON) characteristics of the power
output switching devices. Switching losses are dominat-
ed by the gate charge of the power output switching
devices. At full load, assuming continuous conduction
mode (CCM), a simplified form of the dual converter
losses is given by:
IO12 · (RDSON(HS) · VO1 + RDSON(LS) · [VIN -VO1])
PTOTAL
=
+
VIN
IO22 · (RDSON(HS) · VO2 + RDSON(LS) · [VIN -VO2])
VIN
V
V
1.5V
0.6V
⎛
⎝
⎞
⎛
⎝
⎞
⎠
OUT
R1 =
-1 · R2 =
- 1 · 59kΩ = 88.5kΩ
⎠
REF
+ (tsw · F · [IO1 + IO2] + 2 · IQ) · VIN
The adjustable version of the AAT2515 in combination
with an external feedforward capacitor (C4 and C5 of
Figure 1) delivers enhanced transient response for
extreme pulsed load applications. The addition of the
feedforward capacitor typically requires a larger output
capacitor (C1 and C2) for stability.
IQ is the AAT2515 quiescent current for one channel and
tsw is used to estimate the full load switching losses.
For the condition where channel one is in dropout at
100% duty cycle, the total device dissipation reduces to:
R2, R4 = 59k
R1, R3 (k)
R2, R4 = 221k
PTOTAL = IO12 · RDSON(HS)
VOUT (V)
R1, R3
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
19.6
29.4
39.2
49.9
59.0
68.1
78.7
88.7
118
124
137
187
267
75K
113K
150K
187K
221K
261K
301K
332K
442K
464K
523K
715K
1.00M
IO22 · (RDSON(HS) · VO2 + RDSON(LS) · [VIN -VO2])
+
VIN
+ (tsw · F · IO2 + 2 · IQ) · VIN
Since RDS(ON), quiescent current, and switching losses all
vary with input voltage, the total losses should be inves-
tigated over the complete input voltage range.
Given the total losses, the maximum junction tempera-
ture can be derived from the JA for the TDFN33-12 pack-
age which is 50°C/W.
Table 2: Adjustable Resistor Values
For Use With 0.6V Version.
TJ(MAX) = PTOTAL · ΘJA + TAMB
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DATA SHEET
AAT2515
Dual 600mA, FastTransient High Frequency Buck Converter
3. The feedback trace should be separate from any
power trace and connect as closely as possible to the
PCB Layout
The following guidelines should be used to insure a
proper layout.
load point. Sensing along a high-current load trace
will degrade DC load regulation. If external feedback
resistors are used, they should be placed as closely
as possible to the FB pin. This prevents noise from
being coupled into the high impedance feedback
node.
1. Due to the pin placement of VIN for both converters,
proper decoupling is not possible with just one input
capacitor. The large input capacitor C3 should con-
nect as closely as possible to VIN and GND, as shown
in Figure 2. The additional input bypass capacitor C8
is necessary for proper high frequency decoupling of
the second converter.
2. The output capacitor and inductor should be con-
nected as closely as possible. The connection of the
inductor to the LX pin should also be as short as
possible.
4. The resistance of the trace from the load return to
GND should be kept to a minimum. This will help to
minimize any error in DC regulation due to differ-
ences in the potential of the internal signal ground
and the power ground.
5. For good thermal coupling, PCB vias are required
from the pad for the TDFN paddle to the ground
plane. The via diameter should be 0.3mm to 0.33mm
and positioned on a 1.2 mm grid.
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DATA SHEET
AAT2515
Dual 600mA, FastTransient High Frequency Buck Converter
Design Example
Specifications
VO1 = 2.5V @ 600mA (adjustable using 0.6V version), pulsed load ILOAD = 300mA
VO2 = 1.8V @ 600mA (adjustable using 0.6V version), pulsed load ILOAD = 300mA
VIN = 2.7V to 4.2V (3.6V nominal)
FS
= 1.4 MHz
TAMB = 85°C
2.5V VO1 Output Inductor
µs
µs
(see Table 1)
L1 = 3
⋅ VO1 = 3
⋅ 2.5V = 7.5µH
A
A
For Sumida inductor CDRH3D16, 10μH, DCR = 210m.
⎛
⎞
= 72.3mA
VO1
VO1
2.5
V
2.5V
⎛
⎞
ΔI1 =
⋅ 1 -
⎝
=
⋅ 1 -
⎝
⎠
L1 ⋅ F
VIN
10μH ⋅ 1.4MHz
4.2V
⎠
ΔI1
= 0.6A + 0.036A = 0.64A
2
IPK1 = IO1
+
2
PL1 = IO1 ⋅ DCR = 0.6A2 ⋅ 210mΩ = 75.6mW
1.8V VO2 Output Inductor
µs
µs
(see Table 1)
L2 = 3
⋅ VO2 = 3
⋅ 1.8V = 5.4µH
A
A
For Sumida inductor CDRH3D16, 4.7μH, DCR = 105m.
⎛
⎞
= 156mA
VO2
VO2
1.8
V
1.8V
⎛
⎞
⎠
ΔI2 =
⋅ 1 -
⎝
=
⋅ 1 -
⎝
⎠
L ⋅ F
VIN
4.7μH ⋅ 1.4MHz
4.2V
ΔI2
= 0.6A + 0.078A = 0.68A
2
IPK2 = IO2
+
2
PL2 = IO2 ⋅ DCR = 0.6A2 ⋅ 105mΩ = 37.8mW
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DATA SHEET
AAT2515
Dual 600mA, FastTransient High Frequency Buck Converter
2.5V Output Capacitor
3 · ΔILOAD 3 · 0.3A
VDROOP · FS 0.1V · 1.4MHz
COUT
=
=
= 6.4µF; use 10µF
(VOUT) · (VIN(MAX) - VOUT
)
1
2.5V · (4.2V - 2.5V)
1
·
= 21mArms
IRMS(MAX)
=
·
=
10µH · 1.4MHz · 4.2V
L · F · VIN(MAX)
2· 3
2· 3
Pesr = esr · IRMS2 = 5mΩ · (21mA)2 = 2.2µW
1.8V Output Capacitor
3 · ΔILOAD
VDROOP · FS
3 · 0.3A
COUT
=
=
= 6.4µF; use 10µF
0.1V · 1.4MHz
(VOUT) · (VIN(MAX) - VOUT
)
1
1.8V · (4.2V - 1.8V)
1
·
= 45mArms
IRMS(MAX)
=
·
=
4.7µH · 1.4MHz · 4.2V
L · F · VIN(MAX)
2· 3
2· 3
Pesr = esr · IRMS2 = 5mΩ · (45mA)2 = 10µW
Input Capacitor
Input Ripple VPP = 25mV.
1
1
CIN =
=
= 11.3µF; use 10µF
⎛
VPP
⎞
⎛ 25mV
⎝ 1.2A
⎞
⎠
- ESR · 4 · FS
- 5mΩ · 4 · 1.4MHz
⎝IO1 + IO2
⎠
IO1 + IO2
IRMS(MAX)
=
= 0.6Arms
2
P = esr · IRMS2 = 5mΩ · (0.6A)2 = 1.8mW
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DATA SHEET
AAT2515
Dual 600mA, FastTransient High Frequency Buck Converter
AAT2515 Losses
The maximum dissipation occurs at dropout where VIN = 2.7V. All values assume an ambient temperature of 85°C and
a junction temperature of 120°C.
IO12 · (RDSON(HS) · VO1 + RDSON(LS) · (VIN -VO1)) + IO22 · (RDSON(HS) · VO2 + RDSON(LS) · (VIN -VO2))
PTOTAL
=
VIN
+ (tsw · F · IO2 + 2 · IQ) · VIN
0.62 · (0.725Ω · 2.5V + 0.7Ω · (2.7V - 2.5V)) + 0.62 · (0.725Ω · 1.8V + 0.7Ω · (2.7V - 1.8V))
2.7V
=
+ 5ns · 1.4MHz · 0.6A + 60μA) · 2.7V = 530mW
TJ(MAX) = TAMB + ΘJA · PLOSS = 85°C + (50°C/W) · 530mW = 111°C
Output 1 Enable
VIN
1
2 3
U1
C41
R1
see Table 3
AAT2515
LX1
1
2
3
4
5
6
12
11
10
9
L1
EN1
VIN1
LX1
see Table 3
VO1
FB1
GND
EN2
FB2
GND
C3
GND
VIN2
LX2
C51
LX2
VO2
R3
10μF
see Table 3
L2
see Table 3
8
C11
C6
10μF
0.01μF
7
GND
C21
10μF
R4
R2
59.0k
C7
59.0k
C8
0.01μF
0.1μF
GND
GND
3
2 1
Output 2 Enable
Figure 1: AAT2515 Evaluation Board Schematic.
1. For enhanced transient configuration C5, C4 = 100pF.
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DATA SHEET
AAT2515
Dual 600mA, FastTransient High Frequency Buck Converter
Adjustable Version
(0.6V device)
VOUT (V)
R2, R4 = 59k
R1, R3 (k)
R2, R4 = 221k1
R1, R3 (k)
L1, L2 (μH)
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
19.6
29.4
39.2
49.9
59.0
68.1
78.7
88.7
118
124
137
187
267
75.0
113
150
187
221
261
301
332
442
464
523
715
1000
2.2
2.2
2.2
2.2
2.2
2.2
4.7
4.7
4.7
4.7
6.8
6.8
6.8
Fixed Version
VOUT (V)
R2, R4 Not Used
R1, R3 (k)
L1, L2 (μH)
0.6-3.3V
0
4.7
Table 3: Evaluation Board Component Values.
Figure 2: AAT2515 Evaluation Board Top Side.
Figure 3: AAT2515 Evaluation Board
Bottom Side.
1. For reduced quiescent current, R2 and R4 = 221k.
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DATA SHEET
AAT2515
Dual 600mA, FastTransient High Frequency Buck Converter
Max DC
Current (A)
Size (mm)
LxWxH
Manufacturer
Part Number
Inductance (μH)
DCR ()
Type
Sumida
Sumida
Sumida
Murata
Murata
Coilcraft
Coiltronics
Coiltronics
Coiltronics
CDRH3D16-2R2
CDRH3D16-4R7
CDRH3D16-6R8
LQH2MCN4R7M02
LQH32CN4R7M23
LPO3310-472
2.2
4.7
6.8
4.7
4.7
4.7
4.7
6.8
4.7
1.20
0.90
0.73
0.40
0.45
0.80
0.98
0.82
1.30
0.072
0.105
0.170
0.80
0.20
0.27
0.122
0.175
0.122
3.8x3.8x1.8
3.8x3.8x1.8
3.8x3.8x1.8
2.0x1.6x0.95
2.5x3.2x2.0
3.2x3.2x1.0
3.1x3.1x1.85
3.1x3.1x1.85
5.7x4.4x1.0
Shielded
Shielded
Shielded
Non-Shielded
Non-Shielded
1mm
Shielded
Shielded
1mm Shielded
SD3118-4R7
SD3118-6R8
SDRC10-4R7
Table 4: Typical Surface Mount Inductors.
Manufacturer
Part Number
Value
Temp. Co.
Case
Murata
Murata
Murata
GRM219R61A475KE19
GRM21BR60J106KE19
GRM21BR60J226ME39
4.7μF
10uF
22uF
X5R
X5R
X5R
0805
0805
0805
Table 5: Surface Mount Capacitors.
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DATA SHEET
AAT2515
Dual 600mA, FastTransient High Frequency Buck Converter
Ordering Information
Voltage
Package
Channel 1
0.6V
Channel 2
Marking1
Part Number (Tape and Reel)2
AAT2515IWP-AA-T1
TDFN33-12
0.6V
2XXYY
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.
Legend
Voltage
Code
Adjustable
(0.6V)
A
0.9
1.2
1.5
1.8
1.9
2.5
2.6
2.7
2.8
2.85
2.9
3.0
3.3
4.2
B
E
G
I
Y
N
O
P
Q
R
S
T
W
C
1. XYY = assembly and date code.
2. Sample stock is generally held on part numbers listed in BOLD.
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DATA SHEET
AAT2515
Dual 600mA, FastTransient High Frequency Buck Converter
Package Information
TDFN33-121
Index Area
Detail "A"
0.43 0.05
0.1 REF
C0.3
Pin 1 Indicator
(optional)
3.00 0.05
1.70 0.05
Top View
Bottom View
Detail "A"
0.05 0.05
Side View
All dimensions in millimeters.
1. 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.
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
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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-
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