1
AAT115
1
850kHz 700mA S
y
nchronous Buck DC/DC Converte
r
DATA SHEET
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201991B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013
General Description
The AAT1151 SwitchReg™ is a step-down switching con-
verter ideal for applications where high efficiency is
required over the full range of output load conditions.
The 2.7V to 5.5V input voltage range makes the AAT1151
ideal for single-cell lithium-ion/polymer battery applica-
tions. Capable of more than 700mA with internal
MOSFETs, the current-mode controlled IC provides high
efficiency using synchronous rectification. Fully inte-
grated compensation simplifies system design and low-
ers external parts count.
The device operates at a fixed 850kHz switching fre-
quency and enters Pulse Frequency Modulation (PFM)
mode for light load current to maintain high efficiency
across all load conditions.
The AAT1151 is available in Pb-free MSOP-8 and QFN33-
16 packages and is rated over the -40°C to +85°C tem-
perature range.
Features
• VIN Range: 2.7V to 5.5V
• Up to 95% Efficiency
• High Initial Accuracy ±1%
• 110m RDS(ON) Internal Switches
• <1μA Shutdown Current
• 850kHz Switching Frequency
• Fixed VOUT or Adjustable VOUT ≥1.0V
• Integrated Power Switches
• Synchronous Rectification
• Current Mode Operation
• Internal Compensation
• Stable with Ceramic Capacitors
• PFM for Optimum Efficiency for All Load Conditions
• Internal Soft Start
• Over-Temperature Protection
• Current Limit Protection
• MSOP-8 and QFN33-16 Packages
• -40°C to +85°C Temperature Range
Applications
• Cellular Phones
• Digital Cameras
• MP3 Players
• Notebook Computers
• PDAs
• USB-Powered Equipment
• Wireless Notebook Adapters
Typical Application
OUTPUT
3.0μH
2x 22μF
10μF
0.1μF
100Ω
LX
VP
INPUT
FB
SGND
AAT1151
ENABLE
VCC
PGND
2
AAT115
1
850kHz 700mA Synchronous Buck DC/DC Converte
r
DATA SHEET
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201991B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013
Pin Descriptions
Pin #
Symbol Function
MSOP-8 QFN33-16
14FB
Feedback input pin. This pin is connected to the converter output. It is used to set the output
of the converter to regulate to the desired value via an internal resistive divider. For an ad-
justable output, an external resistive divider is connected to this pin on the 1V model.
2 5, 6 SGND Signal ground. Connect the return of all small signal components to this pin. (See board lay-
out rules.)
37EN
Enable input pin. A logic high enables the converter; a logic low forces the AAT1151 into shut-
down mode reducing the supply current to less than 1μA. The pin should not be left fl oating.
4 9 VCC Bias supply. Supplies power for the internal circuitry. Connect to input power via low pass
fi lter with decoupling to SGND.
5 10, 11, 12 VP Input supply voltage for the converter power stage. Must be closely decoupled to PGND.
6, 7 13, 14, 15 LX Connect inductor to these pins. Switching node internally connected to the drain of both high-
and low-side MOSFETs.
8 1, 2, 3 PGND Main power ground return pin. Connect to the output and input capacitor return. (See board
layout rules.)
8, 16 NC Not internally connected.
EP Exposed paddle (bottom); connect to PGND directly beneath package
Pin Configuration
MSOP-8 QFN33-16
(Top View) (Top View)
1 2
LX
PGND
LX
VP
FB
SGND
EN
VCC
1
2
3
4
8
7
6
5
VP
VP
VP
NC
PGND
PGND
PGND
1
2
3
4
SGND
SGND
EN
16
15
14
13
5
6
7
8
12
11
10
9
NC
VCC
LX
LX
LX
FB
3
AAT115
1
850kHz 700mA Synchronous Buck DC/DC Converte
r
DATA SHEET
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201991B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013
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. Human body model is a 100pF capacitor discharged through a 1.5k resistor into each pin.
3. Mounted on a demo board.
4. Derate 6.7mW/°C above 25°C.
5. Derate 20mW/°C above 25°C.
Absolute Maximum Ratings1
Symbol Description Value Units
VCC, VPVCC, VP to GND 6V
VLX LX to GND -0.3 to VP + 0.3 V
VFB FB to GND -0.3 to VCC + 0.3 V
VEN EN to GND -0.3 to 6 V
TJOperating Junction Temperature Range -40 to 150 °C
VESD ESD Rating2 - HBM 3000 V
Thermal Characteristics3
Symbol Description Value Units
JA Thermal Resistance MSOP-8 150 °C/W
QFN33-16 50
PDMaximum Power Dissipation (TA = 25°C) MSOP-84667 mW
QFN33-1652.0 W
Recommended Operating Conditions
Symbol Description Value Units
T Ambient Temperature Range -40 to 85 °C
4
AAT115
1
850kHz 700mA Synchronous Buck DC/DC Converte
r
DATA SHEET
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201991B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013
1. The AAT1151 is guaranteed to meet performance specifications over the -40°C to +85°C operating range and is assured by design, characterization, and correlation with sta-
tistical process controls.
Electrical Characteristics1
VIN = VCC = VP = 5V, 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 2.7 5.5 V
VOUT Output Voltage Tolerance VIN = VOUT + 0.2 to 5.5V, IOUT = 0 to 700mA -3.0 +3.0 %
VUVLO Under-Voltage Lockout VIN Rising 2.5 V
VIN Falling 1.2
VUVLO(HYS) Under-Voltage Lockout Hysteresis 250 mV
IIL Input Low Current VIN = VFB = 5.5V 1.0 μA
IIH Input High Current VIN = VFB = 0V 1.0 μA
IQQuiescent Supply Current No Load, VFB = 0V, VIN = 4.2V, TA = 25°C 210 300 μA
ISHDN Shutdown Current VEN = 0V, VIN = 5.5V 1.0 μA
ILIM Current Limit TA = 25°C 1.2 A
RDS(ON)H High Side Switch On Resistance TA = 25°C 110 150 m
RDS(ON)L Low Side Switch On Resistance TA = 25°C 100 150 m
Effi ciency IOUT = 300mA, VIN = 3.5V 92 %
VOUT
(VOUT*VIN)Load Regulation VIN = 4.2V, ILOAD = 0 to 700mA 0.9 %
VOUT/VOUT Line Regulation VIN = 2.7V to 5.5V 0.1 %/V
FOSC Oscillator Frequency TA = 25°C 600 850 1200 kHz
VEN(L) Enable Threshold Low 0.6 V
VEN(H) Enable Threshold High 1.4 V
TSD Over-Temperature Shutdown Threshold 140 °C
THYS Over-Temperature Shutdown Hysteresis 15 °C
5
AAT115
1
850kHz 700mA Synchronous Buck DC/DC Converte
r
DATA SHEET
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201991B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013
Typical Characteristics
Efficiency vs. Load Current
(VOUT = 2.5V; L = 4.2μ
μ
H)
Output Current (mA)
Efficiency (%)
50
60
70
80
90
100
1 10 100 1000
Efficiency vs. Load Current
(VOUT = 1.8V)
50
60
70
80
90
100
1 10 100 1000
Load Current (mA)
Efficiency (%)
2.7V
3.6V 4.2V
No Load Supply Current vs. Input Voltage
2.5 3 3.5 4 4.5 5 5.5
Input Voltage (V)
Supply Current (μ
μ
A)
0
50
100
150
200
250
300
T = 85°C
T = -40°CT = 25°C
Frequency vs. Input Voltage
850
860
870
880
890
2.5 3 3.5 4 4.5 5 5.5
Input Voltage (V)
Frequency (kHz)
Output Voltage vs. Temperature
1.78
1.782
1.784
1.786
1.788
1.79
1.792
1.794
-40 -20 0 20 40 60 80 100
Temperature (°°C)
Output Voltage (V)
Load and Line Regulation
Load Current (mA)
VOUT Error (%)
-3.0
-2.0
-1.0
0.0
1.0
2.0
3.0
1 10 100 1000
VIN = 3.6V
VIN = 4.2V
VIN = 2.7V
6
AAT115
1
850kHz 700mA Synchronous Buck DC/DC Converte
r
DATA SHEET
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201991B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013
Typical Characteristics
Switching Frequency vs. Temperature
0
200
400
600
800
1000
1200
-40 -20 0 20 40 60 80 100
Temperature (°
°
C)
Frequency (kHz)
Output Ripple 1.8V, 50mA, VIN = 3.6V
Circuit of Figure 1
Time (2μ
μ
s/div)
Output Voltage
(AC coupled) (top) (mV)
Inductor Current
(bottom) (A)
-60
-50
-40
-30
-20
-10
0
10
20
-0.2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
Line Transient Response 1.8V, 50mA
Circuit of Figure 1
2.8
3
3.2
3.4
3.6
3.8
4
4.2
4.4
Time (20μ
μ
s/div)
Input Voltage
(top) (V)
-40
-20
0
20
40
60
80
100
120
Output Voltage
(bottom) (mV)
Output Ripple 1.8V, 0.7A, VIN = 3.6V
Circuit of Figure 1
Time (2μ
μ
s/div)
Output Voltage
(AC coupled) (top) (mV)
Inductor Current
(bottom) (A)
-60
-50
-40
-30
-20
-10
0
10
20
-0.5
0
0.5
1
1.5
2
2.5
3
3.5
Line Transient Response 1.8V, 0.7A
Circuit of Figure 1
2.8
3
3.2
3.4
3.6
3.8
4
4.2
4.4
Time (20μ
μ
s/div)
Input Voltage
(top) (V)
-40
-20
0
20
40
60
80
100
120
Output Voltage
(bottom) (mV)
Load Transient Response 50mA to 0.7A
VIN = 3.6V −
−
Circuit of Figure 1
Time (200
μ
s/div)
Output Voltage (top) (mV)
(AC coupled)
Inductor Current
(bottom) (A)
-120
-100
-80
-60
-40
-20
0
20
40
-0.5
0
0.5
1
1.5
2
2.5
3
3.5
7
AAT115
1
850kHz 700mA Synchronous Buck DC/DC Converte
r
DATA SHEET
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201991B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013
Typical Characteristics
Soft Start 1.8V, 0.7A, VIN = 3.6V
Circuit of Figure 1
Time (200μ
μ
s/div)
Enable (top)
Output (middle) (V)
Inductor Current
(bottom) (A)
-4
-3
-2
-1
0
1
2
3
4
-0.5
0
0.5
1
1.5
2
2.5
3
3.5
Output Ripple
Circuit of Figure 1
0
5
10
15
20
1 10 100 1000
Output Current (mA)
Ripple (mV)
VIN = 2.7V
VIN = 3.6V
VIN = 4.2V
8
AAT115
1
850kHz 700mA Synchronous Buck DC/DC Converte
r
DATA SHEET
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201991B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013
Operation
Control Loop
The AAT1151 is a peak current mode buck converter. The
inner wide bandwidth loop controls the peak current of
the output inductor. The output inductor current is
sensed through the P-channel MOSFET (high side) and is
also used for short-circuit and overload protection. A
fixed slope compensation signal is added to the sensed
current to maintain stability. The loop appears as a volt-
age programmed current source in parallel with the out-
put capacitor.
The voltage error amplifier output programs the current
loop for the necessary inductor current to force a con-
stant output voltage for all load and line conditions. The
voltage feedback resistive divider is internal, dividing the
output voltage to the error amplifier reference voltage of
1.0V. The voltage error amplifier does not have the large
DC gain typical of most error amplifiers. This eliminates
the need for external compensation components, while
still providing sufficient DC loop gain for load regulation.
The voltage loop crossover frequency and phase margin
are set by the output capacitor value only.
PFM/PWM Operation
Light load efficiency is maintained by way of PFM control.
The AAT1151 PFM control forces the peak inductor cur-
rent to a minimum level regardless of load demand. At
medium to high load demand, this has no effect on cir-
cuit operation and normal PWM controls take over. PFM
reduces the switching frequency at light loads, thus
reducing the associated switching losses.
Soft Start/Enable
Soft start increases the inductor current limit point in
discrete steps when the input voltage or enable input is
applied. It limits the current surge seen at the input and
eliminates output voltage overshoot. When pulled low,
the enable input forces the AAT1151 into a low-power,
non-switching state. The total input current during shut-
down is less than 1μA.
Functional Block Diagram
VP = 2.7V to 5.5VVCC
ENSGND PGND
LOGIC
1.0V REF
Temp.
Sensing
OSC
OP. AMP
LX
FB DH
DL
CMP
1MΩ
9
AAT115
1
850kHz 700mA Synchronous Buck DC/DC Converte
r
DATA SHEET
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201991B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013
Power and Signal Source
Separate small signal ground and power supply pins
isolate the internal control circuitry from the noise asso-
ciated with the output MOSFET switching. The low pass
filter R1 and C2 in schematic Figure 1 filters the noise
associated with the power switching.
Current Limit and
Over-Temperature Protection
For overload conditions, the peak input current is limit-
ed. As load impedance decreases and the output voltage
falls closer to zero, more power is dissipated internally,
raising the device temperature. Thermal protection com-
pletely disables switching when internal dissipation
becomes excessive, protecting the device from damage.
The junction over-temperature threshold is 140°C with
10°C of hysteresis.
Inductor
The output inductor is selected to limit the ripple current
to some predetermined value, typically 20% to 40% of
the full load current at the maximum input voltage.
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.
During overload and transient conditions, the average
current in the inductor can meet or exceed the current
limit point of the AAT1151. These conditions can tolerate
greater saturation in the inductor without degradation in
converter performance. 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 con-
verter efficiency when selecting an inductor.
For a 1.0A load and the ripple set to 40% at the maxi-
mum input voltage, the maximum peak-to-peak ripple
current is 280mA. The inductance value required is
2.84μH.
L = • 1 -
VOUT VOUT
IO • k • FS VIN
= • 1 -
1.5V 1.5V
1A • 0.4 • 850kHz 4.2V
⎛⎞
⎝⎠
⎛⎞
⎛⎞
⎝⎠
⎝⎠
= 2.84μH
The factor “k” is the fraction of full load selected for the
ripple current at the maximum input voltage. For ripple
current at 40% of the full load current, the peak current
will be 120% of full load. Selecting a standard value of
3.0μH gives 38% ripple current. A 3.0μH inductor select-
ed from the Sumida CDRH5D28 series has a 24m DCR
and a 2.4A DC current rating. At full load, the inductor
DC loss is 24mW, which amounts to a 1.6% loss in effi-
ciency.
L1
3.3µH
C3, C4
2x22µF
C1
10µF
R1
100
C2
0.1µF
C1 Murata 10µF 6.3V X5R GRM42-6X5R106K6.3
C3-C4 Murata 22µF 6.3V GRM21BR60J226ME39L X5R 0805
L1 Sumida CDRH3D16-4R7NC or CDRH3D16-3R3NC
R2
100k
1.8V2.7V-4.2V
FB 1
SGND
2
EN
3
VCC
4
LX 6
LX 7
PGND 8
VP
5
U1
AAT1151-MSOP
Efficiency vs. Load Current
(VOUT = 1.8V)
50
60
70
80
90
100
1 10 100 1000
Load Current (mA)
Efficiency (%)
2.7V
3.6V 4.2V
Figure 1: AAT1151 Evaluation Board.
10
AAT115
1
850kHz 700mA Synchronous Buck DC/DC Converte
r
DATA SHEET
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201991B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013
Input Capacitor
The primary function of the input capacitor is to provide
a low impedance loop for the edges of pulsed current
drawn by the AAT1151. A low ESR/ESL ceramic capacitor
is ideal for this function. To minimize stray inductance,
the capacitor should be placed as close as possible to the
IC. This keeps the high frequency content of the input
current localized, minimizing radiated and conducted
EMI while facilitating optimum performance of the
AAT1151. Ceramic X5R or X7R capacitors are ideal for
this function. The size required will vary depending on
the load, output voltage, and input voltage source
impedance characteristics. A typical value is around
10μF. The input capacitor RMS current varies with the
input voltage and the output voltage. The equation for
the RMS current in the input capacitor is:
⎛⎞
IRMS = IO • • 1 -
⎝⎠
VO
VIN
VO
VIN
The input capacitor RMS ripple current reaches a maxi-
mum when VIN is two times the output voltage where it
is approximately one half of the load current. Losses
associated with the input ceramic capacitor are typically
minimal and are not an issue. Proper placement of the
input capacitor can be seen in the reference design lay-
out in Figures 2 and 4.
Output Capacitor
Since there are no external compensation components,
the output capacitor has a strong effect on loop stability.
Lager output capacitance will reduce the crossover fre-
quency with greater phase margin. For the 1.5V 1A
design using the 4.1μH inductor, two 22μF capacitors
provide a stable output. In addition to assisting stability,
the output capacitor limits the output ripple and provides
holdup during large load transitions. The output capaci-
tor RMS ripple current is given by:
1
23
VOUT · (VIN - VOUT)
RMS
IL · FS · VIN
=·
·
For a ceramic capacitor, the ESR is so low that dissipation
due to the RMS current of the capacitor is not a concern.
Tantalum capacitors with sufficiently low ESR to meet
output voltage ripple requirements also have an RMS
current rating well beyond that actually seen in this
application.
Layout
Figures 2 through 5 display the suggested PCB layout for
the AAT1151. The following guidelines should be used to
help ensure a proper layout.
• The input capacitor (C1) should connect as closely as
possible to VP (Pin 5) and PGND (Pin 8).
• C2 and L1 should be connected as closely as possible.
The connection L1 to the LX node should be as short
as possible.
• The feedback trace (Pin 1) should be separate from
any power trace and connect as closely as possible to
the load point. Sensing along a high-current load trace
will degrade DC load regulation.
• The resistance of the trace from the load return to the
PGND (Pin 8) should be kept to a minimum. This will
help to minimize any error in DC regulation due to dif-
ferences in the potential of the internal signal ground
and the power ground.
• Low pass filter R1 and C3 provide a cleaner bias
source for the AAT1151 active circuitry. C3 should be
placed as closely as possible to SGND (Pin 2) and VCC
(Pin 4). See Figures 2 and 7.
11
AAT115
1
850kHz 700mA Synchronous Buck DC/DC Converte
r
DATA SHEET
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201991B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013
Figure 2: MSOP Evaluation Figure 3: MSOP Evaluation
Board Top Layer. Board Bottom Layer.
Figure 4: QFN Evaluation Board Top Side. Figure 5: QFN Evaluation Board Bottom Side.
0
5
10
15
20
25
30
35
40
45
1 1.5 2 2.5 3 3.5 4 4.5 5 5.5
Output Voltage (V)
R3 (k
Ω
)
R4=10kΩ
L1
3.3μH C2, C4
2x 22μF
C1
10μF
R1 100
C3
0.1μF
C1 Murata 10μF 6.3V X5R GRM42-6X5R106K6.3
L1 Sumida CDRH3D16-3R3 NC
R2
100k
C2, C4 Murata 22μF 6.3V GRM21BR60J226ME39L X5R 0805
VO+ 1.25V 0.7A
2.7V - 5.5V
GND
FB 4
SGND
5,6
EN
7
VCC
9
VP
10,11,12
LX 13,14,15
PGND 1,2,3
AAT1151-1.0 R3
2.55k 1%
R4
10kΩ 1%
Figure 6: R3 vs. VOUT for Adjustable Output Figure 7: Adjustable Output Schematic.
Using the AAT1151-1.0V.
12
AAT115
1
850kHz 700mA Synchronous Buck DC/DC Converte
r
DATA SHEET
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201991B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013
Thermal Calculations
There are two types of losses associated with the
AAT1151 output switching MOSFET: switching losses and
conduction losses. Conduction losses are associated with
the RDS(ON) characteristics of the output switching device.
At the full load condition, assuming continuous conduc-
tion mode (CCM), a simplified form of the total losses is
given by:
SW OSIN
IN
IO2 · (RDS(ON)H · VO + RDS(ON)L · (VIN · VO))
P =
FI V
V
+ IQ) · VIN
···
+ (t
where Iq is the AAT1151 quiescent current.
Once the total losses have been determined, the junction
temperature can be derived from the JA for the MSOP-8
package.
TJ = P · θJA + TAMB
Adjustable Output
For applications requiring an output other than the fixed
available, the 1V version can be programmed externally.
Resistors R3 and R4 of Figure 7 force the output to regu-
late higher than 1V. R4 should be 100 times less than the
1M internal resistance of the FB pin (recommended
10k). Once R4 is selected, R3 can be calculated. For a
1.25 volt output with R4 set to 10.0k, R3 is 2.55k.
R3 = (VO - 1) · R4 = 0.25 · 10kΩ = 2.55kΩ
13
AAT115
1
850kHz 700mA Synchronous Buck DC/DC Converte
r
DATA SHEET
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201991B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013
Design Example
Specifications
IOUT = 0.7A
IRIPPLE = 40% of Full Load at Max VIN
VOUT = 1.5V
VIN = 2.7V to 4.2V (3.6V nominal)
FS = 850kHz
TAM = 85°C
Maximum Input Capacitor Ripple
1 0.35Arms, VIN = 2 · VO
OO
RMS O
IN IN
VV
II
VV
⎛⎞
=· · -=
⎝⎠
P = esr · IRMS
2 = 5mΩ · 0.352 A = 0.6mW
Inductor Selection
V
OUT
V
OUT
1.5
V
1.5V
L = ⋅ 1 - = ⋅ 1 - = 4.05μH
I
O
⋅ k ⋅ F
S
V
IN
0.7A ⋅ 0.4 ⋅ 850kHz
4.2V
⎛
⎝⎞
⎠⎛
⎝⎞
⎠
Select Sumida inductor CDRH3D16, 3.3μH, 63m, 1.8mm height.
V
O
V
O
1.5
V
1.5V
ΔI = ⋅ 1 - = ⋅ 1- = 340mA
L ⋅ F
S
V
IN
3.3μH ⋅ 850kHz
4.2V
I
PK
= I
OUT
+ ΔI = 0.7A + 0.17A = 0.87A
2
P = I
O2
⋅ DCR = (0.7)
2
⋅ 63mΩ = 31mW
⎛
⎝⎞
⎠
⎛
⎝⎞
⎠
Output Capacitor Ripple Current
1
23
1 1.5V · (4.2V - 1.5V)
3.3μH · 850kHz · 4.2V
23
RMS
IL · FS · VIN
=·
·
· = 99mArms
·
VOUT · (VIN - VOUT)=
Pesr = esr · IRMS2 = 5mΩ · 992 mA = 50μW
14
AAT115
1
850kHz 700mA Synchronous Buck DC/DC Converte
r
DATA SHEET
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201991B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013
AAT1151 Dissipation
PTOTAL + (tsw • FS • IO + IQ) • VIN
IO2 • (RDS(ON)H • VO + RDS(ON)L • (VIN -VO))
VIN
=
=+ (20nsec • 850kHz • 0.7A + 0.3mA) • 4.2V = 0.145
W
(0.7A)2 • (0.2Ω • 1.5V + 0.187Ω • (4.2V - 1.5V))
4.2V
TJ(MAX) = TAMB + ΘJA • PLOSS = 85°C + 150°C/W • 0.145W = 107°C (MSOP-8
)
= 85°C + 50°C/W • 0.145W = 92°C (QFN33-16)
Manufacturer Part Number Value
Max DC
Current DCR (Ω)
Size (mm)
L x W x H Type
Taiyo Yuden NPO5DB4R7M 4.7μH 1.4A 0.038 5.9 x 6.1 x 2.8 Shielded
Toko A914BYW-3R5M-D52LC 3.5μH 1.34A 0.073 5.0 x 5.0 x 2.0 Shielded
Sumida CDRH5D28-3R0 3.0μH 2.4A 0.024 5.7 x 5.7 x 3.0 Shielded
Sumida CDRH5D28-4R2 4.2μH 2.2A 0.031 5.7 x 5.7 x 3.0 Shielded
Sumida CDRH5D18-4R1 4.1μH 1.95A 0.057 5.7 x 5.7 x 2.0 Shielded
Murata LQH55DN4R7M03 4.7μH 2.7A 0.041 5.0 x 5.0 x 4.7 Non-Shielded
Murata LQH66SN4R7M03 4.7μH 2.2A 0.025 6.3 x 6.3 x 4.7 Shielded
Murata CDRH3D16-3R3 3.3μH 1.1A 0.063 3.8 x 3.8 x 1.8 Shielded
Table 1: Surface Mount Inductors.
Manufacturer Part Number Value Voltage Temp. Co. Case
Murata GRM40 X5R 106K 6.3 10μF 6.3V X5R 0805
Murata GRM42-6 X5R 106K 6.3 10μF 6.3V X5R 1206
Murata GRM21BR60J226ME39L 22μF 6.3V X5R 0805
Murata GRM21BR60J106ME39L 10μF 6.3V X5R 0805
Table 2: Surface Mount Capacitors.
15
AAT115
1
850kHz 700mA Synchronous Buck DC/DC Converte
r
DATA SHEET
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201991B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013
1. Contact local sales office for custom options.
2. XYY = assembly and date code.
3. Sample stock is generally held on part numbers listed in BOLD.
4. 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.
Ordering Information
Output Voltage1Package Marking2Part Number (Tape and Reel)3
1.0V (Adj. VOUT ≥ 1.0V) QFN33-16 JHXYY AAT1151IVN-1.0-T1
1.8V MSOP-8 JIXYY AAT1151IKS-1.8-T1
2.5V QFN33-16 JJXYY AAT1151IVN-2.5-T1
3.3V MSOP-8 NKXYY AAT1151IKS-3.3-T1
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 Information4
MSOP-8
PIN 1
1.95 BSC
0.254 BSC
0.155
±
0.075
0.60
±
0.20
3.00
±
0.10
0.95
±
0.15
0.95 REF
0.85
±
0.10
3.00
±
0.10
10
°
±
5
°
4
°
±
4
°
0.65 BSC 0.30
±
0.08
0.075
±
0.075
4.90
±
0.10
GAUGE PLANE
All dimensions in millimeters.
16
AAT115
1
850kHz 700mA Synchronous Buck DC/DC Converte
r
DATA SHEET
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201991B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 18, 2013
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, specifi cations 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 confl icts, incompatibilities, or other diffi culties 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 specifi cations as a result of design defects, errors, or operation of products outside of pub-
lished parameters or design specifi cations. 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 specifi cations 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
identifi cation 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.
QFN33-16
3.000
±
0.050
Pin 1 Dot By Marking
1.250
±
0.050
0.400
±
0.100
1.250
±
0.050
3.000
±
0.050
0.500
±
0.050
0.900
±
0.100
Pin 1 Identification
C0.3
0.025
±
0.025
0.214
±
0.036
0.230
±
0.050
Top View Bottom View
Side View
1
13
5
9
All dimensions in millimeters.
