SKYWORKS AAT1130IJQ-0.6-T1

DATA SHEET
AAT1130
2.5MHz 400mA Step-Down DC/DC Converter
General Description
Features
The AAT1130 SwitchReg™ is a member of Skyworks' Total
Power Management IC™ product family. The converter
uses a predictive on-time, current-mode step-down control scheme that provides a fixed 2.5MHz switching frequency (under steady state conditions). It allows the
control circuit to react nearly instantly in order to improve
transient response and to enhance stability with the LC
components as small as 1.0μH. The unique architecture
improves transient response while allowing tiny passive
LC filter components. The high switching frequency (up to
2.5MHz) keeps output voltage ripple low.
• 2.5MHz Switching Frequency
• Fast Transient Response with Small LC Output Filter
Components
• Input Voltage Range: 2.7V to 5.5V
• Output Voltage Range: 0.6V to 1.8V
• High 92% Peak Efficiency (VIN = 3.6V, VOUT = 1.8V)
• Low 60μA Quiescent Current
• 400mA Maximum Continuous Output Current
• Internal 150μs Soft-Start Feedback Ramp
• Over-Temperature Protection
• Anti-Ringing Switch to Reduce EMI During Discontinuous
Conduction Mode Operation
• Valley Current Limit Protection
• SC70JW-10 Package
• -40°C to 85°C Temperature Range
The AAT1130 delivers up to 400mA of output current,
while consuming only 60μA of quiescent current. The
AAT1130 regulates an output voltage between 0.6V and
1.8V from an input voltage of 2.7V to 5.5V. The AAT1130's
output voltage is set by an external resistive voltage
divider circuit. Internal MOSFET switches reduce the overall solution size while maintaining high efficiency over a
wide load current range.
Applications
•
•
•
•
•
•
•
The AAT1130 is available in a space-saving 2.0x2.2mm
SC70JW-10 package and is rated over the -40°C to 85°C
temperature range.
Microprocessor/DSP Core and I/O
Mobile Phones
PDAs and Handheld Computers
Digital Cameras
Portable Music Players
Handheld Games
Handheld Instruments
VIN
2.4V to 5.5V
L 1.0μH
CIN
4.7μF
0603
6V
X5R
ON
OFF
3
VP
LX
VCC OUT
AAT1130
FB
6
EN
GND
5
2
C3
100pF
R1
150kΩ
0603 1%
1
7-10
R2
100kΩ
0603 1%
COUT
4.7μF
0603
6V
X5R
1.10
1.6
1.05
1.4
1.00
1.2
0.95
1.0
0.90
0.8
0.85
0.80
0.6
400mA
0.4
100mA
0.75
0.70
Output Current
(bottom) (A)
4
1.0V VOUT
400mA
Output Voltage (top) (V)
Typical Application
0.2
0
Time (5µs/div)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
201977B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 15, 2013
1
DATA SHEET
AAT1130
2.5MHz 400mA Step-Down DC/DC Converter
Pin Descriptions
Pin #
Symbol
1
FB
2
VOUT
3
VCC
4
VP
5
LX
6
7, 8, 9, 10
EN
GND
Function
Output voltage feedback input. FB senses the output voltage through a resistor voltage divider circuit.
Connect the voltage divider from the output voltage to FB. The feedback threshold is 0.6V.
Output voltage sense input. VOUT senses the output voltage. Connect VOUT to the output voltage node
for proper on-time calculation.
Input supply voltage. Connect VCC to the input supply voltage.
Power input supply voltage. Connect VP to the VCC pin, and to the input supply voltage. Bypass VP to
GND with a 2.2μF or greater ceramic capacitor.
Switching node. Connect the LC filter between LX and the load. LX is internally connected to the drain of
the p-channel MOSFET switch and n-channel MOSFET synchronous rectifier.
Enable input. Active logic high.
Ground.
Pin Configuration
SC70JW-10
(Top View)
FB
VOUT
VCC
VP
LX
2
1
10
2
9
3
8
4
7
5
6
GND
GND
GND
GND
EN
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
201977B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 15, 2013
DATA SHEET
AAT1130
2.5MHz 400mA Step-Down DC/DC Converter
Absolute Maximum Ratings1
Symbol
Description
VVCC, VVP
VLX
VFB
VEN
TJ
TLEAD
VCC, VP to GND
LX Voltage to GND
FB Voltage to GND
EN Voltage to GND
Operating Junction Temperature Range
Maximum Soldering Temperature (at leads, 10 sec)
Value
Units
6.0
-0.3 to VVCC\VVP +0.3
-0.3 to VVCC\VVP +0.3
-0.3 to VVCC\VVP +0.3
-40 to 150
300
V
V
V
V
°C
°C
Value
Units
625
160
mW
°C/W
Thermal Information
Symbol
PD
JA
Description
Maximum Power Dissipation
Thermal Resistance2
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 a FR4 board.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
201977B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 15, 2013
3
DATA SHEET
AAT1130
2.5MHz 400mA Step-Down DC/DC Converter
Electrical Characteristics1
VIN = 3.6V, CIN = COUT = 4.7μF, L = 1.5μH. TA = -40°C to 85°C, unless otherwise noted. Typical values are TA = 25°C.
Symbol
Description
VIN
VOUT
Input Voltage
Output Voltage Range
VUVLO
UVLO Threshold
IQ
ISHDN
VFB_ACC
ILIM
RDS(ON)H
RDS(ON)L
fON
tOFF(MIN)
ILXLEAK
IFBLEAK
tS
fS
TSD
THYS
VEN(L)
VEN(H)
IEN
Quiescent Current
Shutdown Current
Feedback Voltage Accuracy
Valley Current Limit
High Side Switch On-Resistance
Low Side Switch On-Resistance
Switch On-Time
Minimum Off-Time
LX Leakage Current
FB Leakage Current
Startup Time
Switching Frequency
Over-Temperature Shutdown Threshold
Over-Temperature Shutdown Hysteresis
Enable Threshold Low
Enable Threshold High
Enable Pin Current
Conditions
Min
Typ
2.7
0.6
VIN rising
Hysteresis
Not Switching
EN = GND
TA = 25°C, No Load
TA = 25°C
100
60
0.59
500
VIN = 3.6V, VOUT = 1.2V
VIN = 5.5, VLX = 0 to VIN
VFB = 5.5V, VEN = 0V, Adj Only
From EN Asserted to Output Regulation
VOUT = 1.2V, 400mA Load
0.6
650
0.35
0.25
120
75
Max
Units
5.5
1.8
2.65
V
V
V
mV
μA
μA
V
mA
Ω
Ω
ns
ns
μA
μA
μs
MHz
°C
°C
V
V
μA
90
1.0
0.61
1
0.2
150
2.5
140
15
0.6
VIN = VFB =5.5V
1.4
-1.0
1.0
1. The AAT1130 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured by design, characterization, and correlation with statistical process controls.
4
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
201977B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 15, 2013
DATA SHEET
AAT1130
2.5MHz 400mA Step-Down DC/DC Converter
Typical Characteristics
Efficiency vs. Load Current
Output Voltage Error vs. Load Current
(VOUT = 1V)
(VOUT = 1V)
100
Output Voltage Error (%)
2
90
Efficiency (%)
80
70
60
50
VIN = 2.7V
VIN = 3.6V
VIN = 4.2V
VIN = 5V
VIN = 5.5V
40
30
20
10
0
0.0001
0.001
0.01
0.1
VIN = 2.7V
VIN = 3.6V
VIN = 4.2V
VIN = 5V
VIN = 5.5V
1.5
1
0.5
0
-0.5
-1
-1.5
-2
-2.5
-3
0.0001
1
0.001
Load Current (A)
Line Regulation
1
(VOUT = 1.8V)
100
1
IOUT = 1mA
IOUT = 10mA
IOUT = 100mA
IOUT = 300mA
IOUT = 500mA
0.75
0.5
0.25
90
80
Efficiency (%)
Output Voltage Error (%)
0.1
Efficiency vs. Load Current
(VOUT = 1V)
0
-0.25
-0.5
70
60
50
40
VIN = 2.7V
VIN = 3.6V
VIN = 4.2V
VIN = 5V
VIN = 5.5V
30
20
-0.75
10
-1
2.7
3.2
3.7
4.2
4.7
5.2
0
0.0001
5.7
0.001
Input Voltage (V)
Output Voltage Difference (%)
0.5
0
-0.5
-1
-2
-3
0.0001
VIN = 2.7V
VIN = 3.6V
VIN = 4.2V
VIN = 5V
VIN = 5.5V
0.001
0.01
Load Current (A)
1
(VOUT = 1.8V)
1
-2.5
0.1
Line Regulation
(VOUT = 1.8V)
-1.5
0.01
Load Current (A)
Output Voltage Error vs. Load Current
Output Voltage Error (%)
0.01
Load Current (A)
0.1
1
1
IOUT = 1mA
IOUT = 10mA
IOUT = 100mA
IOUT = 300mA
0.75
0.5
0.25
0
-0.25
-0.5
-0.75
-1
2.7
3.2
3.7
4.2
4.7
5.2
5.7
Input Voltage (V)
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5
DATA SHEET
AAT1130
2.5MHz 400mA Step-Down DC/DC Converter
Typical Characteristics
Supply Current vs. Supply Voltage
(Switching)
Switching Frequency vs. Input Voltage
(VOUT = 1V; CIN = COUT = 2.2µF; L = 1µH)
Switching Frequency (MHz)
Supply Current (µA)
100
95
90
85
80
75
70
65
60
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
4
3.75
3.5
3.25
3
2.75
2.5
2.25
2
2.7
3.1
3.5
Switching Frequency (MHz)
On-Time (ns)
5.5
(VOUT = 1.8V; CIN = COUT = 2.2µF; L = 1.5µH))
150
100
0
3.1
3.5
3.9
4.3
4.7
5.1
5.5
3
2.75
2.5
2.25
2
1.75
1.5
1.25
1
2.7
3.1
3.5
Input Voltage (V)
400
350
300
250
200
150
100
50
0
3.5
3.9
4.3
Input Voltage (V)
4.7
5.1
5.5
Switching Frequency Variation (%)
On-Time vs. Input Voltage
3.1
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
(VOUT = 1.8V; CIN = COUT = 2.2µF; L = 1.5µH))
On-Time (ns)
5.1
Switching Frequency vs. Input Voltage
50
6
4.7
On-Time vs. Input Voltage
200
2.7
4.3
(VOUT = 1V; CIN = COUT = 2.2µF; L = 1µH))
250
2.7
3.9
Input Voltage (V)
Supply Voltage (V))
Switching Frequency Variation
vs. Load Current
20
15
10
5
VIN = 2.7V
VIN = 3.3V
VIN = 3.6V
VIN = 4.2V
VIN = 5V
VIN = 5.5V
0
-5
-10
-15
-20
200
250
300
350
400
450
500
Load Current (mA)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
201977B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 15, 2013
550
600
DATA SHEET
AAT1130
2.5MHz 400mA Step-Down DC/DC Converter
Typical Characteristics
Supply Current vs. Temperature
Output Voltage Error vs. Temperature
0.2
Output Voltage Error (%)
Supply Current (µA)
100
90
80
70
60
50
40
30
20
0.1
0
-0.1
-0.2
-0.3
-0.4
-0.5
-40
-15
10
35
60
-40
85
-15
10
Temperature (V)
35
60
85
Temperature (°C)
RDS(ON) vs. Temperature
Switching Frequency vs. Output Voltage
400
RDS(ON) (mΩ)
350
300
250
200
150
100
PMOS
NMOS
50
0
-40
-15
10
35
60
Switching Frequency (MHz)
(IOUT = 500mA)
450
85
3.75
3.25
2.75
2.25
1.75
1.25
0.6
0.9
1.2
1.5
1.8
Output Voltage (V)
Temperature (°C)
0.7
1.80
0.6
1.75
0.5
1.70
0.4
300mA
1.65
0.3
1.60
0.2
100mA
1.55
0.1
1.55
0.0
Time (5µs/div)
1.90
0.8
1.85
0.7
1.80
0.6
1.75
0.5
1.70
0.4
300mA
1.65
0.3
1.60
0.2
100mA
1.55
0.1
1.50
0
Output Current
(bottom) (A)
0.8
1.85
Output Current
(bottom) (A)
1.90
Output Voltage (top) (V)
Load Transient
(VOUT = 1.8V; VIN = 3.6V; COUT = 4.7µF; L = 1.5µH)
Output Voltage (top) (V)
Load Transient
(VOUT = 1.8V; VIN = 3.6V; COUT = 4.7µF; CFF = 100pF; L = 1.5µH)
Time (5µs/div)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
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7
DATA SHEET
AAT1130
2.5MHz 400mA Step-Down DC/DC Converter
Typical Characteristics
1.4
1.80
1.2
1.75
1.0
1.70
0.8
1.65
500mA
0.6
1.60
0.4
1.55
0.2
10mA
1.6
1.55
1.4
1.50
1.2
1.45
1.0
1.40
1.35
0.2
0
Load Transient
(VOUT = 1V; VIN = 3.6V; COUT = 4.7µF; CFF = 100pF; L = 1µH)
0.8
0.7
1.50
0.6
1.45
0.5
1.40
0.4
300mA
1.35
0.3
1.30
0.2
100mA
1.25
0.1
1.20
0
1.10
1.6
1.05
1.4
1.00
1.2
0.95
1.0
0.90
0.8
0.85
0.80
0.4
100mA
0.75
0.70
0.2
0
Time (5µs/div)
Load Transient
Load Transient
(VOUT = 1V; VIN = 3.6V; COUT = 4.7µF; L = 1µH)
(VOUT = 1V; VIN = 3.6V; COUT = 4.7µF; CFF = 100pF; L = 1µH)
1.6
1.00
1.2
0.95
1.0
0.90
0.8
0.85
0.6
400mA
0.75
0.4
100mA
0.70
0.2
0
Time (5µs/div)
1.10
1.6
1.05
1.4
1.00
1.2
0.95
1.0
0.90
0.8
0.85
500mA
0.6
0.80
0.4
0.75
10mA
0.2
0
0.70
Time (5µs/div)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
201977B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 15, 2013
Output Current
(bottom) (A)
1.4
Output Current
(bottom) (A)
1.05
Output Voltage (top) (V)
1.10
0.80
0.6
400mA
Output Current
(bottom) (A)
1.60
1.55
Output Voltage (top) (V)
Load Transient
(VOUT = 1.5V; VIN = 3.6V; COUT = 4.7µF; L = 1.5µH)
Output Current
(bottom) (A)
Output Voltage (top) (V)
0.4
10mA
Time (5µs/div)
Time (5µs/div)
Output Voltage (top) (V)
0.6
1.30
1.25
Time (5µs/div)
8
0.8
500mA
1.20
0
1.50
1.60
Output Current
(bottom) (A)
1.6
1.85
Output Current
(bottom) (A)
1.90
Output Voltage (top) (V)
Load Transient
(VOUT = 1.5V; VIN = 3.6V; COUT = 4.7µF; CFF = 100pF; L = 1.5µH)
Output Voltage (top) (V)
Load Transient
(VOUT = 1.8V; VIN = 3.6V; COUT = 4.7µF; CFF = 100pF; L = 1.5µH)
DATA SHEET
AAT1130
2.5MHz 400mA Step-Down DC/DC Converter
Soft-Start
Line Transient
(VOUT = 1.8V; VIN = 3.6V; COUT = 4.7µF; L = 1.5µH)
(VOUT = 1.8V; COUT = 4.7µF; L = 1.5µH)
3.6V
200mA
(100mA/Div)
0mA
Time (100µs/div)
6.6
1.85
6.1
1.80
5.6
1.75
5.1
1.70
4.6
1.65
4.1
1.60
3.6
1.55
3.1
1.50
2.6
Output Voltage
(bottom) (V)
1.8V
(1V/Div)
0V
Output Voltage (top) (V)
1.90
(2V/Div)
0V
Output Current
(bottom) (A)
Enable Voltage (top) (V)
Output Voltage (middle) (V)
Typical Characteristics
Time (10µs/div)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
201977B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 15, 2013
9
DATA SHEET
AAT1130
2.5MHz 400mA Step-Down DC/DC Converter
Functional Block Diagram
VP
VCC
Control and
FET Driver
Logic Circuitry
Shoot
Through
Protection
Current
Limit
Comparator
LX
VILIM
Current
Sense
Amplifier
Error
Comparator
GND
VOUT
FB
EN
Soft-Start
+
VREF
-
GND
Functional Description
The AAT1130 is a high performance 400mA 2.5MHz
(maximum switching frequency during steady-state
operation) monolithic step-down converter. It minimizes
external component size, enabling the use of a tiny 0603
inductor that is only 1mm tall, and optimizes efficiency
over the complete load range. Apart from the small
bypass input capacitor, only a small L-C filter is required
at the output. Typically, a 1μH inductor and a 4.7μF
ceramic capacitor are recommended for <1.2V output
voltage applications (see table of values).
Only three external power components (CIN, COUT, and L)
are required. Output voltage is programmed with external feedback resistors, ranging from 0.6V to 1.8V. An
additional feed-forward capacitor can also be added to
the external feedback to provide improved transient
response (see Figure 1).
10
The input voltage range is 2.7V to 5.5V. The converter
efficiency has been optimized for all load conditions,
ranging from no load to 400mA.
The internal error comparator and incorporated compensation provide excellent transient response, load, and line
regulation. Soft-start eliminates any output voltage overshoot when the enable or the input voltage is applied.
Control Loop
The AAT1130 uses a current-mode control scheme that
allows it to operate at very high switching frequencies.
The current-mode control scheme operates with a predicted on-time for a given output to input voltage ratio.
The on-time varies inversely proportional to the input
voltage and proportional to the output voltage giving the
regulator a fixed switching frequency when in steadystate. This allows the use of very small external inductor
and capacitor. The small size coupled with the low quies-
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
201977B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 15, 2013
DATA SHEET
AAT1130
2.5MHz 400mA Step-Down DC/DC Converter
cent current and automatic transition to variable switching frequency mode makes it ideal for small battery
operated applications.
Light Load Operation
The AAT1130 monitors the synchronous rectifier current
and when the current drops to zero, it turns off the synchronous rectifier to emulate an actual rectifier. This
allows the regulator to operate in discontinuous conduction mode. In this mode the on-time remains the same
as it is in continuous conduction mode, and therefore the
inductor ripple current remains the same in both modes.
But reduced load current requires more time for the output capacitor to discharge to the regulation voltage
reducing the switching frequency. This has the added
benefit of reducing the switching transition losses
improving efficiency at light loads.
The only requirement for stability is that the crossover
frequency be much less than the 2.5MHz switching frequency. The crossover frequency can be as high as 1/2
of the switching frequency, or 1.25MHz. Therefore calculate the output capacitor by the equation:
COUT >
VOUT
2π · 0.6V · 60mΩ · 1.25MHz
Example:
Given that VOUT = 1.5V, then COUT > 5.3μF, therefore a
4.7μF capacitor is the closest standard value that can be
used for 1.2V to 1.5V output.
Due to the unique control method, the “inside” current
control loop does not have the inherent instability that
plagues most fixed frequency current-mode DC-DC regulators.
Stability
Soft-Start
The AAT1130 requires no additional compensation components to guarantee stability. The only requirement for
stability is to choose the appropriate output capacitor.
When the AAT1130 is enabled, it enters soft-start mode.
In this mode, the output voltage slowly rises over 150μs
allowing the output capacitor to charge without drawing
excessive input current. This feature prevents overstressing the battery or other input power source.
Current-mode control simplifies compensation by controlling the inductor current to regulate the output voltage.
This approximates a single pole response in the loop gain
even though a complex pole pair exists due to the LC filter. Therefore the crossover frequency is approximated as
the DC loop gain multiplied by the single pole. The
AAT1130 DC loop gain is a function of the 60mΩ current
sense resistor and is determined by the equation:
VOUT RLOAD
ALOOP(DC) = 0.6V · 60mΩ
And the dominant pole frequency is:
fP =
1
2π · RLOAD · COUT
Therefore the crossover frequency is:
fC = ALOOP(DC) · fP
=
VOUT
2π · 0.6V · 60mΩ · COUT
Valley Current Limit
The AAT1130 includes a cycle-by-cycle, valley current
limit to prevent damage to itself or the external components. The valley current limit uses the low-side-NChannel synchronous rectifier to monitor the inductor
current. If the measured current exceeds the valley current limit, the AAT1130 keeps the low-side synchronous
rectifier on until the current drops below the current
limit. Along with the predictive on-time control scheme,
the valley current limit protection allows the converter to
control and limit the inductor current, even with output
overload or short-circuit fault condition.
Since the AAT1130 uses a predictive on-time architecture (constant on-time with input feed-forward), the
actual output current capability is a function of the
inductor ripple current (ΔIL) and the current limit comparator delay (see Figure 1):
IOUT_MAX = ILIM_VALLEY +
IOUT_MAX = ILIM_VALLEY +
∆IL
VOUT
· tDELAY
2
L
VIN - VOUT
VOUT
VOUT
·
· tSW · tDELAY
2L
VIN
L
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11
DATA SHEET
AAT1130
2.5MHz 400mA Step-Down DC/DC Converter
Where tSW is the switching period constant (typically
360ns) as defined by the on-time specification in the
Electrical Characteristics table, and tDELAY is the currentlimit comparator delay (typically 150ns).
Applications Information
Inductor Selection
The step-down converter uses a predictive on-time control scheme with internal slope and current compensation. The internal current compensation eliminates the
"minimum, output capacitor ESR" stability requirement
commonly required with this control architecture. However,
the current compensation requires that the inductor current down slope to maintain a sufficient signal-to-noise
ratio. The inductor current down-slope is defined by:
TON
ΔIL
di
V
= OUT
dt
L
IOUT(MAX)
ILIMIT
TDELAY
Figure 1: Output Current to
Valley Current-Limit Relationship
Anti-Ringing Switch
The AAT1130 includes an anti-ringing switch that dissipates any energy left in the inductor when the current is
approximately zero. The anti-ringing switch turns on
when both the p-channel switch and n-channel synchronous rectifier are off and the inductor current is approximately zero. The switch shorts the LX and VOUT nodes
together, effectively shorting the inductor. The low onresistance of the anti-ringing switch dissipates any
energy left in the inductor preventing ringing at light
loads. When either the switch or synchronous rectifier
are on, the anti-ringing switch remains off.
Over-Temperature
The AAT1130 includes thermal protection that automatically turns off the regulator when the die temperature
exceeds a safe level. The thermal protection turns on at
a die temperature of 140°C and has a 15°C hysteresis.
resulting in an inductor recommendation to keep the
μH
inductance value equal to the output voltage L = V V to
di
maintain the appropriate dt.
OUT
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 saturation 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. See Table 2 for suggested inductor values
and vendors.
Input Capacitor
Select a 4.7μF to 10μF X7R or X5R ceramic capacitor for
the input. Always examine the ceramic capacitor DC
voltage coefficient characteristics when selecting the
proper value. For example, the capacitance of a 10μF,
6.3V, X5R ceramic capacitor with 5.0V DC applied is
actually about 6μF.
The input capacitor provides a low impedance loop for
the edges of pulsed current drawn by the AAT1130. 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 (C1) can be
seen in the evaluation board layouts in Figures 4 and 5.
12
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DATA SHEET
AAT1130
2.5MHz 400mA Step-Down DC/DC Converter
A laboratory test set-up typically consists of two long
wires running from the bench power supply to the evaluation 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 during 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 supply, most applications do not
exhibit this problem. In applications where the input
power source lead inductance cannot be reduced to a
level that does not affect the converter performance, a
high ESR tantalum or aluminum electrolytic should be
placed in parallel with the low ESR, ESL bypass ceramic.
This dampens the high Q network and stabilizes the system.
Output Capacitor
The output capacitor limits the output ripple and provides holdup during large load transitions. A 4.7μF to
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 necessary for low output ripple.
The internal voltage loop compensation also limits the
minimum output capacitor value to 4.7μF. This is due to
its effect on the loop crossover frequency (bandwidth),
phase margin, and gain margin. Increased output capacitance will reduce the crossover frequency with greater
phase margin.
Feedback Resistor Selection
Resistors R1 and R2 of Figure 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
while maintaining good noise immunity, the minimum
suggested value for R2 is 59kΩ. Although a larger value
will further reduce quiescent 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 59kΩ for good noise immunity
or 221kΩ for reduced no load input current.
R1 =
1.5V
VOUT
VFB -1 · R2 = 0.6V - 1 · 59kΩ = 88.5kΩ
The AAT1130, combined with an external feedforward
capacitor (C3 in Figure 2), delivers enhanced transient
response for extreme pulsed load applications. The addition of the feedforward capacitor typically requires a
larger output capacitor C1 for stability.
VOUT (V)
R2 = 59kΩ R1
(kΩ)
R2 = 221kΩ
R1 (kΩ)
0.9
1
1.1
1.2
1.3
1.4
1.5
1.8
29.4
39.2
49.9
59.0
68.1
78.7
88.7
118
113
150
187
221
261
301
332
442
Table 1: Feedback Resistor Values.
Thermal Calculations
CFF
R1
FB
R2
Figure 2: AAT1130 External Resistor
Output Voltage Programming.
There are three types of losses associated with the
AAT1130 step-down 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
dominated by the gate charge of the power output
switching devices. At full load, assuming continuous conduction mode (CCM), a simplified form of the losses is
given by:
PTOTAL =
IO2 · (RDS(ON)H · VO + RDS(ON)L · [VIN - VO])
VIN
+ (tsw · FS · IO + IQ) · VIN
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13
DATA SHEET
AAT1130
2.5MHz 400mA Step-Down DC/DC Converter
IQ is the step-down converter quiescent current. The
term tsw is used to estimate the full load step-down converter switching losses. For the condition where the
step-down converter is in dropout at 100% duty cycle,
the total device dissipation reduces to:
Layout
The suggested PCB layout for the AAT1130 is shown in
Figures 4 and 5. The following guidelines should be used
to help ensure a proper layout:
1.
2
O
PTOTAL = I
· RDS(ON)H + IQ · VIN
Since RDS(ON), quiescent current, and switching losses all
vary with input voltage, the total losses should be investigated over the complete input voltage range. Given the
total losses, the maximum junction temperature can be
derived from the θJA for the SC70JW-10 package which
is 160°C/W.
2.
3.
TJ(MAX) = PTOTAL · ΘJA + TAMB
4.
14
The input capacitor (C1) should connect as closely as
possible to the VCC/VP and GND pins.
C1 and L1 should be connected as closely as possible. The connection of L1 to the LX pin should be as
short as possible.
The feedback trace or FB pin for adjustable output
voltage 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. If external feedback resistors are
used, they should be placed as closely as possible to
the FB pin for adjustable output voltage to minimize
the length of the high impedance feedback trace.
The resistance of the trace from the load return to
the GND pins 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
AAT1130
2.5MHz 400mA Step-Down DC/DC Converter
R2
59k
R1
VIN
GND
C3
100pF
VOUT
C1
4.7μF
U1
FB
GND
2
VOUT
GND
3
VCC
GND
8
4
VP
GND
7
EN
6
5
LX
C2
4.7μF
U1
C1, C2
C3
R1
R2
L1
10
VIN
9
1
2
B
A
C
3
AAT1130_ ADJ
L1
VOUT
GND
1
VOUT
1V
1.5V
1.8V
L1
1μH
1.5μH
1.8μH, 2.2μH
J1 HEADER
AAT1130 Analogic Technologies, 2.5MHz, 400mA Buck Converter
Cap, MLC, 4.7μF/6.3V, 0805
Cap, MLC, 100pF/6.3V, 0402 (optional)
Carbon film resistor, 0402 (adjust to output voltage)
Carbon film resistor, 59kΩ, 0402
LQM2HP-GO, 1.5μH, Murata, ISAT = 1.5A, DCR = 70mΩ;
or VLF3010A, 1.5μH, TDK, ISAT = 1.2A, DCR = 68mΩ
Figure 3: AAT1130 Evaluation Board Schematic.
Figure 4: AAT1130 Evaluation Board
Top Side PCB Layout.
Figure 5: AAT1130 Evaluation Board
Bottom Side PCB Layout.
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15
DATA SHEET
AAT1130
2.5MHz 400mA Step-Down DC/DC Converter
Manufacturer
Part Number/Type
LQM2HP_G0
Murata
LQH32P_N0
GLC2518
TDK
VLF3010A
VLF3010S
Inductance
(μH)
Rated Current
(mA)
DCR (mΩ)
(typ)
1
1.5
2.2
1
1.5
2.2
1
2.2
1.5
2.2
1
2.2
1600
1500
1300
2050
1750
1600
2.8
2.45
1200
1000
1700
1100
55
70
80
45
57
76
20
25
68
100
41
77
Size (mm)
LxWxH
2.5x2x1
3.2x2.5x1.6
2.5x1.8x1.8
2.8x2.6x1
3.0x2.8x1
Table 2: Suggested Inductor Components.
Manufacturer
Part Number
Value
Voltage
Temp. Co.
Case
AVX
0603ZD225K
C1608X5R1C225K
C1608X5R1A475K
C2012X5R1A106K
C3216X5R1A226K
GRM188R61A225K
GRM219R61A106K
GRM31CR71A226K
LMK107BJ475KA
2.2μF
2.2μF
4.7μF
10μF
22μF
2.2μF
10μF
22μF
4.7μF
10
16
10
10
10
10
10
10
10
X5R
0603
TDK
Murata
Taiyo Yuden
0603
X5R
X5R
X7R
X5R
Table 3: Suggested Capacitor Components.
16
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0805
1206
0603
0805
1206
0603
DATA SHEET
AAT1130
2.5MHz 400mA Step-Down DC/DC Converter
Ordering Information
Output Voltage
Package
Marking1
Part Number (Tape and Reel)2
Adjustable
SC70JW-10
2VXXY
AAT1130IJQ-0.6-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 Information
SC70JW-10
2.20 ± 0.20
1.75 ± 0.10
0.40 BSC
0.225 ± 0.075
Top View
0.100
7° ± 3°
0.45 ± 0.10
4° ± 4°
0.05 ± 0.05
0.15 ± 0.05
1.10 MAX
0.85 ± 0.15
2.00 ± 0.20
2.10 ± 0.30
Side View
End View
All dimensions in millimeters.
1. XYY = assembly and date code.
2. Sample stock is generally held on part numbers listed in BOLD
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17
DATA SHEET
AAT1130
2.5MHz 400mA Step-Down DC/DC Converter
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