201931B.pdf

DATA SHEET
AAT1142
800mA Voltage-Scaling Step-Down Converter
General Description
Features
The AAT1142 SwitchReg is a dynamically programmable
2.2MHz step-down converter with an input voltage range
of 2.7V to 5.5V and output from 0.6V to 2.0V. Its low
supply current, high level of integration, and small footprint make the AAT1142 the ideal choice for microprocessor core power in systems such as smartphones.
• VIN Range: 2.7V to 5.5V
• VOUT Programmable Range: 0.6V to 2.0V
• Dynamic Voltage Management:
▪ 50mV Output Resolution
▪ Fast, Stable Response
• Serial Control Options:
▪ I2C Two-Wire Interface
▪ S2Cwire Single-Wire Interface
• 800mA Output Current
• Up to 93% Efficiency
• Line, Load Regulation Less Than ±0.5%
• 2.2MHz Switching Frequency
• Ultra-Small External Filter
• Low 35μA No Load Quiescent Current
• 100% Duty Cycle Low Dropout Operation
• Internal Soft Start
• Over-Temperature Protection
• Current Limit Protection
• Multi-Function MODE/SYNC Pin:
▪ PFM/PWM for High Efficiency
▪ PWM Only for Low Noise
▪ Clock Input to Synchronize to System Clock
• TDFN33-12 Package
• Temperature Range: -40°C to +85°C
The 2.2MHz switching frequency allows the use of a
small external inductor and capacitors. Peak current
mode control and internal compensation provide stable
operation and fast voltage response without over/undershoot or ringing.
The AAT1142 delivers up to 800mA of output current
while consuming 35μA of typical no load quiescent current. Dynamic Voltage Management is provided through
I2C or Skyworks' S2Cwire™ (Simple Serial Control™)
single wire interface. The user can program the output
from 0.6V to 2.0V in 50mV steps.
The AAT1142 optimizes power efficiency throughout the
load range via PWM/PFM mode. Pulling the MODE/SYNC
pin high enables PWM Only mode, maintaining constant
frequency and low noise across the operating range.
Alternatively, the converter may be synchronized to an
external clock input via the MODE/SYNC pin. Overtemperature and short-circuit protection safeguard the
AAT1142 and system components from damage.
Applications
•
•
•
•
•
•
•
The AAT1142 is available in a Pb-free, low-profile
3x3x0.8mm TDFN33-12 package. The device is rated
over the -40°C to +85°C temperature range.
Camcorders
Cellular Phones and Smartphones
Digital Still Cameras
Handheld Instruments
Microprocessor / DSP Core
MP3, Portable Music, and Portable Media Players
PDAs and Handheld Computers
Typical Application
VOUT: 0.6V to 2.0V
800mA Maximum
VIN: 2.7V to 5.5V
Efficiency vs. Load
(VOUT = 1.8V)
L1
PVIN, VIN
100
LX
2.2μH
AAT1142
FB
C1
10μF
MODE/SYNC
PGND
SDA
SCL
I 2C
S Cwire*
AGND
*Optional S2Cwire or I2C Input
80
70
VIN = 4.2V
60
VIN = 5.0V
50
PWM Only
Mode
40
EN/SET
2
VIN = 3.6V VIN = 2.7V
90
Efficiency (%)
C2
4.7μF
30
0
1
10
100
1000
Output Current (mA)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201931B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 17, 2012
1
DATA SHEET
AAT1142
800mA Voltage-Scaling Step-Down Converter
Pin Descriptions
Pin Number
Symbol
12
LX
11
PGND
10
MODE/SYNC
9
8
SDA
SCL
7
EN/SET
6
FB
4, 5
3
1
2
EP
AGND
VIN
PVIN
N/C
Function
Connect the output inductor to this pin. The switching node is internally connected to
the drain of both high- and low-side MOSFETs.
Main power ground return pin. Connect to the output and input capacitor return.
Connect to ground for PFM/PWM mode and optimized efficiency throughout the load
range. Connect to high for low noise PWM Only operation under all operating conditions. Connect to an external clock for synchronization (PWM Only).
I2C control pin: Data input.
I2C control pin: Clock input.
I2C enable pin. Pull high to enable the AAT1142; pull low to disable the AAT1142.
Also serves as S2Cwire input for programmable output voltages.
Feedback input pin. This pin is connected directly to the converter output for programmable output.
Ground connection pin.
Input voltage for the converter.
Input voltage for the power switches.
Not connected.
Exposed paddle (bottom); connect to ground as closely as possible to the device.
Pin Configuration
TDFN33-12
(Top View)
PVIN
N/C
VIN
AGND
AGND
FB
2
1
12
2
11
3
10
4
9
5
8
6
7
LX
PGND
MODE/SYNC
SDA
SCL
EN/SET
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201931B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 17, 2012
DATA SHEET
AAT1142
800mA Voltage-Scaling Step-Down Converter
Absolute Maximum Ratings1
Symbol
Description
VIN, PVIN
VLX
VFB
VSDA/SCL
Input Voltage and Input Power to GND
LX to GND
FB to GND
SDA/SCL to GND
VMODE/SYNC, VEN/SET
TJ
TLEAD
Value
6.0
-0.3 to VIN + 0.3
-0.3 to VIN + 0.3
-0.3 to 6.0
Units
V
MODE/SYNC and EN/SET to GND
-0.3 to 6.0
Operating Junction Temperature Range
Maximum Soldering Temperature (at leads, 10 sec)
-40 to 150
300
°C
Value
Units
2.0
50
W
°C/W
Thermal Information2
Symbol
PD
JA
Description
Maximum Power Dissipation3
Thermal Resistance
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.
3. Derate 20mW/°C above 25°C.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201931B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 17, 2012
3
DATA SHEET
AAT1142
800mA Voltage-Scaling Step-Down Converter
Electrical Characteristics1
L = 2.2μH, CIN = COUT = 10μF, VIN = 3.6V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA =
25°C.
Symbol
Description
Conditions
Step-Down Converter
Input Voltage
VIN
UVLO Threshold
VUVLO
VOUT
VOUT
VSLEW
IQ
ISHDN
ILIM
RDS(ON)H
RDS(ON)L
ILXLEAK
VOUT/
VOUT*VIN
ROUT
TS
FOSC
FSYNC
TSD
THYS
EN/SET and
VEN/SET(L)
VEN/SET(H)
TEN/SET(L)
TEN/SET(H)
TOFF
TLATCH
IEN/SET
Output Voltage Tolerance
VOUT Programmable Range
Output Voltage Programming Slew Rate
Quiescent Current
Shutdown Current
P-Channel Current Limit
High Side Switch On Resistance
Low Side Switch On Resistance
LX Leakage Current
Line Regulation
Output Impedance
Start-Up Time
Oscillator Frequency
SYNC Frequency Range
Over-Temperature Shutdown Threshold
Over-Temperature Shutdown Hysteresis
MODE/SYNC
Enable Threshold Low
Enable Threshold High
EN/SET Low Time
EN/SET High Time
EN/SET Timeout
EN/SET Latch Timeout
Input Low Current
VMODE/SYNC(L)
Enable Threshold Low
VMODE/SYNC(H)
Enable Threshold High
IMODE/SYNC
Input Low Current
Min
Typ
2.7
VIN Rising
Hysteresis
VIN Falling
IOUT = 0mA to 800mA, VIN = 2.7V to 5.5V
Max
Units
5.5
2.7
V
250
2.0
-3.0
0.6
COUT = 10μF
No Load
EN/SET = AGND = PGND
3.0
2.0
10
35
70
1.0
1.0
0.29
0.24

1
0.2
k
μs
100
2.2
1.0
3.0
140
15
VEN/SET < 0.6V
VEN/SET > 1.4V
VEN/SET < 0.6V
VEN/SET > 1.4V
VIN = VFB = 5.5V
50
-1.0
VIN ·
0.7
-1.0
MHz
°C
0.6
1.4
0.3
μA
%/V
250
From Enable to Output Regulation
μA
A
VIN = 5.5V, VLX = 0V to VIN
VIN = 2.7V to 5.5V
mV
V
%
V
mV/μs
75
75
500
500
1.0
VIN ·
0.4
1.0
V
μs
μA
V
μA
1. The AAT1142 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 • sales@skyworksinc.com • www.skyworksinc.com
201931B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 17, 2012
DATA SHEET
AAT1142
800mA Voltage-Scaling Step-Down Converter
Characteristics of SDA and SCL Bus Lines
Standard Mode
Parameter
Symbol
SCL Clock Frequency Hold Time for START Condition; After this
Period, the First Clock Pulse is Generated
LOW Period of the SCL Clock
HIGH Period of the SCL Clock
Set-up Time for a Repeated START Condition
Data in Hold Time
Data in Set-Up Time
Set-Up Time for STOP Condition
Bus Free Time Between a STOP and START Condition
Input Low Level
Input High Level
Min
fSCL
tHD;STA
tLOW
tHIGH
tSU;STA
tHD;DAT
tSU;DAT
tSU;STO
tBUF
VIL
VIH
Max
Fast Mode
Min
100
4.0
4.7
4.0
4.7
0
350
4.0
4.7
3.45
0.6
1.3
0.6
0.6
0
350
0.6
1.3
VIN· 0.3
VIN · 0.7
Max
Units
400
kHz
μs
0.9
μs
μs
VIN · 0.3
VIN · 0.7
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V
5
DATA SHEET
AAT1142
800mA Voltage-Scaling Step-Down Converter
Typical Characteristics
Efficiency vs. Load
DC Regulation
(VOUT = 0.9V)
(VOUT = 0.9V)
2.0
100
Efficiency (%)
Output Accuracy (%)
VIN = 3.6V VIN = 2.7V
90
VIN = 4.2V
80
70
60
50
40
PWM Only
Mode
VIN = 5.0V
30
20
0
1
10
100
1.0
VIN = 2.7V
VIN = 4.2V
-1.0
0
1
Output Accuracy (%)
Efficiency (%)
(VOUT = 1.0V)
VIN = 4.2V
70
60
PWM Only
Mode
VIN = 5.0V
40
30
1.0
1
10
100
VIN = 2.7V
VIN = 4.2V
1000
0
1
(VOUT = 1.2V)
PWM Only
Mode
60
50
VIN = 5.0V
30
20
0
1
10
Output Current (mA)
6
1000
2.0
Output Accuracy (%)
Efficiency (%)
DC Regulation
(VOUT = 1.2V)
70
40
100
Efficiency vs. Load
VIN = 4.2V
80
10
Output Current (mA)
VIN = 3.6V VIN = 2.7V
90
VIN = 5.0V
-1.0
Output Current (mA)
100
VIN = 3.6V
0.0
-2.0
20
0
1000
2.0
VIN = 3.6V VIN = 2.7V
50
100
DC Regulation
(VOUT = 1.0V)
80
10
Output Current (mA)
Efficiency vs. Load
90
VIN = 5.0V
-2.0
1000
Output Current (mA)
100
VIN = 3.6V
0.0
100
1000
1.0
VIN = 2.7V
VIN = 3.6V
0.0
VIN = 4.2V
VIN = 5.0V
-1.0
-2.0
0
1
10
100
Output Current (mA)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201931B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 17, 2012
1000
DATA SHEET
AAT1142
800mA Voltage-Scaling Step-Down Converter
Typical Characteristics
Efficiency vs. Load
DC Regulation
(VOUT = 1.8V)
(VOUT = 1.8V)
2.0
100
Efficiency (%)
Output Accuracy (%)
VIN = 3.6V VIN = 2.7V
90
80
70
VIN = 4.2V
60
VIN = 5.0V
50
PWM Only
Mode
40
30
1.6
1.2
VIN = 5.0V
0.8
VIN = 4.2V
0.4
0.0
VIN = 2.7V
-0.4
-0.8
VIN = 3.6V
-1.2
-1.6
-2.0
0
1
10
100
1000
0
1
Output Current (mA)
100
1000
Output Current (mA)
Soft Start
Line Regulation
(VIN = 3.6V; VOUT = 1.8V; IOUT = 800mA)
(VOUT = 1.0V)
3.5
1.00
3.0
3
0.75
2.0
2.5
1.0
2
0.0
1.5
-1.0
1
-2.0
0.5
-3.0
0
-4.0
-0.5
Output Accuracy (%)
4.0
Inductor Current
(bottom) (A)
Output and Enable Voltage
(top) (V)
10
0.50
IOUT = 650mA
0.25
0.00
-0.25
-0.50
-1.00
2.5
Time (50μs/div)
IOUT = 0mA
IOUT = 100mA
-0.75
3.0
3.5
4.0
4.5
5.0
5.5
Output Voltage Accuracy vs. Temperature
Switching Frequency vs. Temperature
(VIN = 3.6V; VOUT = 1.0V; IOUT = 400mA)
(VIN = 3.6V; VOUT = 1.0V; IOUT = 400mA)
2.0
4.0
1.5
2.0
1.0
Variation (%)
Accuracy (%)
Input Voltage (V)
0.5
0.0
-0.5
-1.0
-2.0
-4.0
-6.0
-8.0
-1.5
-2.0
-40
0.0
-30
-20
-10
0
10
20
30
40
Temperature (°°C)
50
60
70
80
-10.0
-40
-30
-20
-10
0
10
20
30
40
50
60
70
80
Temperature (°°C)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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DATA SHEET
AAT1142
800mA Voltage-Scaling Step-Down Converter
Typical Characteristics
P-Channel RDS(ON) vs. Input Voltage
N-Channel RDS(ON) vs. Input Voltage
450
450
125°C
400
100°C
RDS(ON)L (mΩ
Ω)
RDS(ON)H (mΩ
Ω)
400
85°C
350
300
25°C
250
100°C
2.5
3
3.5
4
4.5
5
5.5
6
6.5
85°C
300
250
25°C
200
200
150
2.5
Input Voltage (V)
3
3.5
4
4.5
5
5.5
6
6.5
Input Voltage (V)
Load Transient Response
(400mA to 800mA; VIN = 3.6V; VOUT = 1.0V)
2.6
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0.0
-0.2
3.0
2.8
2.6
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
-0.1
-0.2
Time (50μs/div)
Load and Inductor Current
(bottom) (200mA/div)
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
Output Voltage
(top) (V)
Load Transient Response
(10mA to 400mA; VIN = 3.6V; VOUT = 1.2V)
Load and Inductor Current
(bottom) (200mA/div)
Output Voltage
(top) (V)
125°C
350
Time (50μs/div)
No Load Quiescent Current vs. Input Voltage
Line Response
(VOUT = 1.8V)
(VOUT = 1.2V; IOUT = 650mA)
85°C
45
25°C
40
-40°C
35
30
25
2.5
3.0
3.5
4.0
4.5
Input Voltage (V)
5.0
5.5
6.0
Output Voltage
(top) (VAC)
50
20
8
0.2
6.0
0.1
5.5
0.0
5.0
-0.1
4.5
-0.2
4.0
-0.3
3.5
-0.4
3.0
55
Time (500μs/div)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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Input Voltage
(bottom) (V)
Supply Current (µA)
60
DATA SHEET
AAT1142
800mA Voltage-Scaling Step-Down Converter
Typical Characteristics
Output Ripple
Output Ripple
(VIN = 4.2V; VOUT = 0.8V; No Load)
(VIN = 4.2V; VOUT = 0.8V; IOUT = 650mA)
Output Voltage
(top) (V)
0.80
0.06
0.04
0.75
0.70
0.02
0.65
0.00
-0.02
0.60
0.82
0.80
0.81
0.78
0.80
0.76
0.79
0.74
0.78
0.72
0.77
0.70
0.76
0.68
0.75
0.66
0.74
0.64
0.73
0.62
0.72
Time (4μs/div)
Output Programming Step
from 1.2V to 0.9V
(VIN = 3.6V; ROUT = 1.85Ω
Ω)
(VIN = 3.6V; ROUT = 1.85Ω
Ω)
1.30
0.90
1.20
0.85
1.20
0.85
1.10
0.80
1.10
0.80
1.00
0.75
1.00
0.75
0.90
0.70
0.90
0.70
0.80
0.65
0.80
0.65
0.70
0.60
0.70
0.60
0.60
0.55
0.60
0.55
0.50
0.50
0.50
0.50
0.40
0.45
0.40
0.45
0.30
0.40
0.30
0.40
Output Voltage
(top) (V)
0.90
Output Current
(bottom) (A)
1.30
Output Current
(bottom) (A)
Output Voltage
(top) (V)
0.60
Time (200ns/div)
Output Programming Step
from 0.9V to 1.2V
Time (50μs/div)
Inductor Current
(bottom) (A)
0.08
Inductor Current
(bottom) (A)
0.85
Output Voltage
(top) (V)
0.10
0.90
Time (50μs/div)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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9
DATA SHEET
AAT1142
800mA Voltage-Scaling Step-Down Converter
Functional Block Diagram
VIN
FB
PVIN
MODE/SYNC
Voltage
Reference
Err.
Amp.
DH
Logic
EN/SET
LX
DL
SDA
SCL
Control
Logic
PGND
AGND
Functional Description
The AAT1142 is a high performance, 800mA step-down
converter with an input voltage range from 2.7V to 5.5V.
The AAT1142 uses Dynamic Voltage Management, which
allows the system host to quickly set the output voltage
through the integrated I2C or S2Cwire interface. Through
this interface, the host can change the output voltage to
track processor idle and active states, greatly extending
battery life without degrading system performance. I2C
provides an industry-standard, dual-line interface, while
S2Cwire provides a single-line, high-speed serial interface.
The 2.2MHz switching frequency allows the use of small
external components. Only three external components
10
are needed to program the output from 0.6V to 2.0V.
Typically, one 4.7μF capacitor, one 10μF capacitor, and
one 2.2μH inductor are required.
The integrated low-loss MOSFET switches provide up to
93% efficiency. PFM operation maintains high efficiency
under light load conditions (typically <50mA). Pulling the
MODE/SYNC pin high allows optional PWM Only low noise
mode. This maintains constant frequency and low output
ripple across all load conditions. Alternatively, the IC can
be synchronized to an external clock via the MODE/SYNC
input. External synchronization can be maintained
between 1MHz and 3MHz.
At low input voltages, the converter dynamically adjusts
the operating frequency prior to dropout to maintain the
required duty cycle and provide accurate output regula-
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201931B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 17, 2012
DATA SHEET
AAT1142
800mA Voltage-Scaling Step-Down Converter
tion. Output regulation is maintained until the dropout
voltage, or minimum input voltage, is reached.
The AAT1142 achieves better than ±0.5% output regulation across the input voltage and output load range.
Maximum continuous load is 800mA. A current limit of
1A (typical) protects the IC and system components
from short-circuit damage. Typical no load quiescent current is 35μA.
Thermal protection completely disables switching when
the maximum junction temperature is detected. The
junction over-temperature threshold is 140°C with 15°C
of hysteresis. Once an over-temperature or over-current
fault condition is removed, the output voltage automatically recovers.
Peak current mode control and optimized internal compensation provide high loop bandwidth and excellent
response to input voltage and fast load transient events.
The output voltage is stable across all operating conditions, ensuring fast transitions with no overshoot or ringing. Soft start eliminates output voltage overshoot when
the enable or the input voltage is applied. Under-voltage
lockout prevents spurious start-up events.
Control Loop
The AAT1142 is a peak current mode step-down converter. The current through the P-channel MOSFET (high
side) is sensed for current loop control, as well as shortcircuit and overload protection. A fixed slope compensation signal is added to the sensed current to maintain
stability for duty cycles greater than 50%. The peak current mode loop appears as a voltage-programmed current source in parallel with the output capacitor.
The output of the voltage error amplifier programs the
current mode loop for the necessary peak switch current
to force a constant output voltage for all load and line
conditions. Internal loop compensation terminates the
transconductance voltage error amplifier output. Loop
stability and fast transient response are maintained
across the entire input and output voltage range with a
small 2.2μH output inductor and 10μF output capacitor.
Soft Start/Enable
Soft start limits the current surge seen at the input and
eliminates output voltage overshoot. When pulled low,
the enable input forces the AAT1142 into a low-power,
non-switching state. The total input current during shutdown is less than 1μA. The turn-on time from EN to
output regulation is 100μs (typical).
Alternatively, the EN/SET pin serves as the input for
S2Cwire single line control. Details of S2Cwire operation
and timing diagrams are provided in the Applications
Information section of this datasheet.
Current Limit and
Over-Temperature Protection
Switching is terminated after entering current limit for a
series of pulses to minimize power dissipation and
stresses under overload and short-circuit conditions.
Switching is terminated for seven consecutive clock
cycles after a current limit has been sensed for a series
of four consecutive clock cycles.
Thermal protection completely disables switching when
internal dissipation becomes excessive. The junction
over-temperature threshold is 140°C with 15°C of hysteresis. Once an over-temperature or over-current fault
condition is removed, the output voltage automatically
recovers.
Under-Voltage Lockout
Internal bias of all circuits is controlled via the VIN input.
Under-voltage lockout (UVLO) guarantees sufficient VIN
bias and proper operation of all internal circuitry prior to
activation.
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11
DATA SHEET
AAT1142
800mA Voltage-Scaling Step-Down Converter
Applications Information
I2C START and STOP Conditions
The AAT1142 output voltage may be programmed from
0.6V to 2.0V through I2C or S2Cwire serial interface.
When using I2C or S2Cwire, the output voltage can be
programmed across the entire output voltage range or in
increments as small as ±50mV (see Figure 1).
START and STOP conditions are initialized by the I2C bus
master. The master determines the START (beginning)
and STOP (end) of a transfer with the slave device. Prior
to initiating a START or after STOP, both the SDA and
SCL lines are in bus-free mode. Bus-free mode is when
SDA and SCL are both in the high state (see Figure 2).
The AAT1142 is compatible with the I2C interface, which
is a widely used two-line serial interface. The I2C twowire communications bus consists of SDA and SCL lines.
SDA provides data, while SCL provides clock input. SDA
data consists of an address bit sequence followed by a
data bit sequence. SDA data transfer is synchronized to
SCL rising clock edges.
When using the I2C interface, EN/SET is pulled high to
enable the output or low to disable the output. To ensure
a disable event, the EN/SET pulse width must be greater
than the latch time (500μs maximum).
The I2C serial interface requires a master to initiate all
the communications with slave devices. The I2C protocol
is a bidirectional bus allowing both read and write actions
to take place; while the AAT1142 is a slave device and
only supports the write protocol.
The AAT1142 is a receiver-only (or write-only) slave
device and the Read/Write (R/W) bit is set low. The
AAT1142 address is preset to 0x14 (Hex).
I2C Address Bit Map
Figure 3 illustrates the address bit map format. The 7-bit
address is sent with the Most Significant Bit (MSB) first
and is valid when SCL is high. This is followed by the R/W
bit in the Least Significant Bit (LSB) location. The R/W
bit determines the direction of the transfer (‘1’ for read,
‘0’ for write). The AAT1142 is a write-only device and
this bit must be set low when communicating with the
AAT1142. The Acknowledge bit (ACK) is set to low by the
AAT1142 slave to acknowledge receipt of the address.
2.5
Output Voltage Level (V)
I2C Serial Interface
2.0
1.5
1.2
(default)
1.0
0.5
0.0
1
3
5
7
9
11
13
15
17
19
21
23
25
27
29
31 32
I C/S Cwire Register
2
2
Figure 1: AAT1142 Graphical Output Voltage
Programming Map.
12
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DATA SHEET
AAT1142
800mA Voltage-Scaling Step-Down Converter
STOP
START
SDA
SDA
SCL
SCL
Figure 2: I2C Start and Stop Conditions.
START: A High “1” to Low “0” Transition on the SDA Line While SCL is High “1”
STOP: A Low “0” to High “1” Transition on the SDA Line While SCL is High “1”
SCL
1
2
3
4
5
6
7
A5
A4
A3
A2
A1
A0
MSB
SDA
A6
8
9
LSB
R/W
ACK
Slave Address
Figure 3: I2C Address Bit Map;
7-bit Slave Address (A6-A0), 1-bit Read/Write (R/W), 1-bit Acknowledge (ACK).
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13
DATA SHEET
AAT1142
800mA Voltage-Scaling Step-Down Converter
I2C Data Bit Map
I2C Software Protocol
Figure 4 illustrates the data bit format. The 8-bit data is
always sent with the most significant bit first and is valid
when SCL is high. The ACK bit is set low by the AAT1142
slave device to acknowledge receipt of the data.
An I2C master / slave data transfer, detailing the address
and data bits, is shown in Figure 5. The programming
sequence is as follows:
1.
2.
3.
4.
5.
6.
I2C Acknowledge Bit
The ACK bit is the ninth bit in the address and data byte.
The master must first release the SDA line, and then the
slave will pull the SDA line low. The AAT1142 sends a low
bit to acknowledge receipt of each byte. This occurs during the ninth clock cycle of Address and Data transfers
(see Figures 4 and 5).
SCL
1
Send a start condition
Send the I2C slave address with the R/W bit set low
Wait for acknowledge within the clock cycle
Send the data bits
Wait for acknowledge within the clock cycle
Send the stop condition
I2C Output Voltage Programming
The AAT1142 output voltage is programmed through the
I2C interface according to Table 1. The data register
encoded on the SCL and SDA lines determines the output voltage set-point after initial start-up. Upon powerup and prior to I2C programming, the default output
voltage is set to 1.8V.
2
3
4
5
6
7
D6
D5
D4
D3
D2
D1
8
MSB
SDA
9
LSB
D7
D0
ACK
Data
Figure 4: I2C Data Bit Map;
8-bit Data (D7-D0), 1-bit Acknowledge (ACK).
SCL
1
2
3
0
0
1
4
5
6
7
0
0
Slave Address
Start
0
1
8
9
R/W
ACK
0
0/1
1
2
3
4
0/1
0/1
0/1
0/1
5
6
7
8
0/1
0/1
0/1
0/1
Data
9
ACK Stop
0/1
7-bit address (0x14)
Figure 5: I2C SCL, SDA Transfer Protocol Example;
7-bit Slave Address (A6-A0 = 0x14), 1-bit Read/Write (R/W = 0), 1-bit Acknowledge (ACK),
8-bit Data (D7-D0), 1-bit Acknowledge (ACK).
14
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DATA SHEET
AAT1142
800mA Voltage-Scaling Step-Down Converter
Data Bits
Data Register
D7
D6
D5
D4
D3
D2
D1
D0
Output Voltage (V)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
0
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0.60
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20 (default)
1.25
1.30
1.35
1.40
1.45
1.50
1.55
1.60
1.65
1.70
1.75
1.80
1.85
1.90
1.95
2.00
2.00
2.00
2.00
Table 1: AAT1142 I2C Output Voltage Programming Map (X = don’t care).
S2Cwire Serial Interface
S2Cwire Serial Interface Timing
Skyworks' S2Cwire serial interface is a proprietary highspeed single-wire interface. The S2Cwire interface records
rising edges of the EN/SET input and decodes them into
one of 32 registers which determines the output voltage,
as shown in Table 2. Each state corresponds to an output
voltage setting.
The S2Cwire serial interface has flexible timing. Data can
be clocked-in at speeds up to 1MHz. After data has been
submitted, EN/SET is held high to latch the data for a
period TLAT. The output is subsequently changed to the
predetermined voltage. When EN/SET is set low for a
time greater than TOFF, the AAT1142 is disabled. When
disabled, the data register is reset to the default value.
When using the S2Cwire interface, both I2C inputs should
be tied to the ground return. This disables the I2C functionality.
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15
DATA SHEET
AAT1142
800mA Voltage-Scaling Step-Down Converter
S2Cwire Timing Diagram
THI
TLO
TOFF
T LAT
EN/SET
1
2
n-1
n ≤ 64
0
Data Reg
Rising Clock
Edges/Data
Register
Output
Voltage
(V)
Rising Clock
Edges/Data
Register
Output
Voltage
(V)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
No change
0.65
0.70
0.75
0.80
0.85
0.90
0.95
1.00
1.05
1.10
1.15
1.20 (default)
1.25
1.30
1.35
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
1.40
1.45
1.50
1.55
1.60
1.65
1.70
1.75
1.80
1.85
1.90
1.95
2.00
2.00
2.00
2.00
Table 2: AAT1142 S2Cwire Output Voltage
Programming Map.
n
0
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.
The 2.2μH CDRH2D14 series Sumida inductor has a
94m DCR and a 1.5A DC current rating. At full 800mA
load, the inductor DC loss is 60mW which gives a 4.8%
loss in efficiency for an 800mA, 1.0V output.
Input Capacitor
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 voltage and
is a maximum when VIN is double the output voltage.
Component Selection
Inductor Selection
The step-down converter uses peak current mode control 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 programmable
AAT1142 is 0.61A/μs. This equates to a slope compensation that is 75% of the inductor current down slope for a
1.8V output and 2.2μH inductor.
0.75 · VO 0.75 · 1.8V
A
m=
=
= 0.61
L
2.2μH
μs
16
CIN =
V ⎞
VO ⎛
· 1- O
VIN ⎝
VIN ⎠
⎛ VPP
⎞
- ESR · FS
⎝ IO
⎠
VO ⎛
V ⎞
1
· 1 - O = for VIN = 2 · VO
VIN ⎝
VIN ⎠
4
CIN(MIN) =
1
⎛ VPP
⎞
- ESR · 4 · FS
⎝ IO
⎠
Always examine the ceramic capacitor DC voltage coefficient characteristics when selecting the proper value. For
example, the capacitance of a 10F, 6.3V, X5R ceramic
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DATA SHEET
AAT1142
800mA Voltage-Scaling Step-Down Converter
capacitor with 5.0V DC applied is actually about 6μF.
Output Capacitor
The maximum input capacitor RMS current is:
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. A smaller capacitor may result in
slightly increased no load output regulation and output
ripple with input voltages above 5V. This should be verified under actual operating conditions.
IRMS = IO ·
VO ⎛
V ⎞
· 1- O
VIN ⎝
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 ⎛
V ⎞
· 1- O =
VIN ⎝
VIN ⎠
D · (1 - D) =
0.52 =
1
2
for VIN = 2 · VO
IRMS(MAX) =
V
⎛
IO
2
V ⎞
The term VINO · ⎝1 - VINO ⎠ appears in both the input voltage
ripple and input capacitor RMS current equations and 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 input capacitor provides a low impedance loop for
the edges of pulsed current drawn by the AAT1142. 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.
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 capacitor should be placed in parallel
with the low ESR, ESL bypass ceramic capacitor. This
dampens the high Q network and stabilizes the system.
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. 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:
COUT =
3 · ΔILOAD
VDROOP · FS
Once the average inductor current increases to the DC
load level, the output voltage recovers. The above equation 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 4.7F. 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.
Thermal Calculations
There are three types of losses associated with the
AAT1142 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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17
DATA SHEET
AAT1142
800mA Voltage-Scaling Step-Down 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 AAT1142 is used to
help ensure a proper layout.
1.
2.
PTOTAL = IO2 · 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 JA for the TDFN33-12 package which is 50°C/W.
3.
4.
TJ(MAX) = PTOTAL · ΘJA + TAMB
5.
6.
The input capacitor should connect as closely as possible to VIN and PGND.
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 pin should be separate from any power
trace and connected close to the VOUT terminal.
Sensing along a high-current load trace will degrade
VOUT load regulation.
The resistance of the trace from the GND terminal to
PGND 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.
Connect unused signal pins to ground to avoid
unwanted noise coupling. When using S2Cwire, connect SDA and SCL to ground to disable I2C functionality.
Connect the exposed paddle (EP) to the GND plane.
Manufacturer
Part Number
Inductance (μH)
Max DC
Current (A)
DCR ()
Size (mm)
LxWxH
Type
Sumida
Sumida
Taiyo Yuden
Taiyo Yuden
CDRH3D16-2R2
CDRH2D14-2R2
NR3010T2R2M
CBC3225T2R2MR
2.2
2.2
2.2
2.2
1.20
1.50
1.10
1.13
0.072
0.094
0.095
0.080
3.8x3.8x1.8
3.2x3.2x1.55
3.0x3.0x1.0
3.2x2.5x2.5
Shielded
Shielded
Shielded
Non-Shielded
Table 3: Typical Surface Mount Inductors.
Manufacturer
Part Number
Type
Value
Voltage
Temp. Co.
Case
Murata
Murata
Murata
Murata
GRM188R60J106ME47D
GRM21BR60J106KE19L
GRM188R60J475KE19D
GRM21BR61A475KA73L
Ceramic
Ceramic
Ceramic
Ceramic
10
10
4.7
4.7
6.3
10
6.3
10
X5R
X5R
X5R
X5R
0603
0805
0603
0805
Table 4: Surface Mount Capacitors.
18
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DATA SHEET
AAT1142
800mA Voltage-Scaling Step-Down Converter
Ordering Information
Package
Marking
Part Number (Tape and Reel)
TDFN33-12
AAT1142-1.2
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
TDFN33-121
Index Area
0.40 ± 0.05
0.1 REF
C0.3
0.45 ± 0.05
2.40 ± 0.05
3.00 ± 0.05
Detail "A"
3.00 ± 0.05
1.70 ± 0.05
Top View
Bottom View
0.23 ± 0.05
Pin 1 Indicator
(optional)
0.05 ± 0.05
0.23 ± 0.05
0.75 ± 0.05
Detail "A"
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.
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19
DATA SHEET
AAT1142
800mA Voltage-Scaling Step-Down Converter
Copyright © 2012 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. Skyworks 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 hereunder, 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, INCLUDING 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 environmental 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 published 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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Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
201931B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • May 17, 2012