Skyworks LMK212BJ475MG 600ma voltage-scaling step-down converter for rf power amplifiers with bypass switch Datasheet

DATA SHEET
AAT1171
600mA Voltage-Scaling Step-Down Converter
for RF Power Amplifiers with Bypass Switch
General Description
Features
The AAT1171 SwitchReg™ dynamically controls the operating voltage of a WCDMA or CDMA power amplifier
inside single-cell, lithium-ion battery-powered systems.
The AAT1171 outputs a voltage between 0.6V and 3.6V,
thereby optimizing the amplifier efficiency at both low
and high transmit levels.
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The AAT1171 output voltage is controlled via an analog
signal from the baseband processor. It can deliver
600mA of continuous load current while maintaining a
low 45μA of no load quiescent current. The 2MHz switching frequency minimizes the size of external components
while keeping switching losses low. To further improve
system efficiency, an 85mΩ bypass MOSFET transistor is
also included to allow the PA to be powered directly from
the battery.
The AAT1171 maintains high efficiency thoughout the
entire load range in Light Load (LL) mode, and can be
forced into Pulse Wide Modulation (PWM) mode for low
noise operation or can be synchronized to an external
clock.
The AAT1171 is available in a Pb-free, space-saving
TDFN33-12 or 12-pin wafer-level chip scale package
(WLCSP) and is rated over the -40°C to +85°C temperature range.
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VIN Range: 2.7V to 5.5V
Variable Output Voltage: 0.6V to 3.6V
600mA Output Current
DAC Input: 0.2V to 1.2V
High Output Accuracy: ±3%
45μA No Load Quiescent Current
Internal Soft Start Limits Startup Current and Output
Voltage Overshoot
Synchronizable to External 19.8MHz System Clock
Over-Temperature and Current Limit Protection
Integrated 85mΩ Bypass MOSFET
2MHz Operation
PWM/LL Control with Override
Fast Start-Up:
▪ 50μs (AAT1171-4, AAT1171-5)
▪ 150μs (AAT1171-1)
100% Duty Cycle Operation
<30μs Output Voltage Response Time
3x3mm 12-Pin TDFN or 1.535x2.235mm 12-Pin
WLCSP Package
Temperature Range: -40°C to +85°C
Applications
• WCDMA or CDMA PA in Cellular Phones, Smartphones,
Feature Phones, etc.
• Express Card
• PCMCIA Data Cards
Typical Application
L1
2.2μH
VIN
LX
VCC
–
COUT
4.7μF
VOUT
BYPASS
–
CIN
4.7μF
COUT
10μF
VOUT
MODE/SYNC
EN
DAC
VCC2 VCONT
GNDx2
VREF
DAC
Baseband
Processor
AAT1171-5
BYPASS
MODE/SYNC
EN
DAC
0.6V - 3.6V
LX
VCC
AAT1171-1/
AAT1171-4
CIN
4.7μF
L1
4.7μH
VIN
0.6V - 3.6V
TX
RX
VCC2 VCONT
GNDx2
VCC2
VREF
PA
DAC
Baseband
Processor
VCC2
PA
TX
RX
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
201999B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 20, 2013
1
DATA SHEET
AAT1171
600mA Voltage-Scaling Step-Down Converter
for RF Power Amplifiers with Bypass Switch
Pin Descriptions
Pin #
TDFN33-12
WLCSP-12
Symbol
1
N/A
N/C
2, 3
5, 9
VOUT
4
7
VCC
5
6
AGND
6
1
DAC
7
2
EN
8
3
BYPASS
9
4
MODE/SYNC
10
11
12
8, 11
VIN
PGND
12
10
LX
EP
N/A
Function
Not connected.
Feedback input pin. This pin is connected to the converter output. It is used to
complete the control loop, regulating the output voltage to the desired value.
When in bypass mode, a low resistance MOSFET is connected between this pin
and VIN.
Bias supply. Supply power for the internal circuitry. Connect to input power via
low pass filter with decoupling to AGND.
Analog ground. Connect the return of all small signal components to this pin.
Control voltage input from a DAC. Input voltage between 0.2V and 1.2V to control output voltage of the converter. Force pin to 1.3V for bypass switch enable.
Enable DC/DC converter, active high.
Enable control to bypass the DC/DC converter when PA transmitting at full
power from low battery voltage. Active high.
This pin is used to program the device between PWM and LL mode:
HIGH - PWM Mode Only
LOW - LL Mode: PWM operation for loads above 100mA and variable switching
frequency for loads below 100mA. Connecting the SYNC pin to the system clock
(19.8MHz) will override the internal clock and force the switching frequency to
the external clock frequency divided by 10.
Input supply voltage for the converter. Must be closely decoupled.
Main power ground. Connect to the output and input capacitor return.
Switching node. Connect the inductor to this pin. It is connected internally to
the drain of both low- and high-side MOSFETs.
Exposed paddle (bottom). Connect to ground directly beneath the package.
Pin Configuration
TDFN33-12
(Top View)
WLCSP-5
(Top View)
11: PGND
8: PGND
N/C
VOUT
VOUT
VCC
AGND
DAC
1
12
2
11
3
10
4
9
5
8
6
7
LX
PGND
VIN
MODE/SYNC
BYPASS
EN
LX
10
11
12
VIN
VOUT
9
8
7
VCC
MODE/SYNC
4
5
6
AGND
BYPASS
3
2
1
DAC
5: VOUT
2: EN
2
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
201999B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 20, 2013
DATA SHEET
AAT1171
600mA Voltage-Scaling Step-Down Converter
for RF Power Amplifiers with Bypass Switch
Absolute Maximum Ratings1
Symbol
VCC, VIN
VLX
VOUT
VN
TJ
TLEAD
Description
Input Voltage and Bias Power to GND
LX to GND
VOUT to GND
EN, DAC, BYPASS, MODE/SYNC to GND
Operating Junction Temperature Range
Maximum Soldering Temperature (at leads, 10 sec)
Value
Units
6.0
-0.3 to VIN + 0.3
-0.3 to VIN + 0.3
-0.3 to 6.0
-40 to 150
300
V
V
V
V
°C
°C
Value
Units
Thermal Information2
Symbol
Description
PD
Maximum Power Dissipation, TA = 25°C
θJA
Thermal Resistance, TA = 25°C
TDFN33-122, 3
WLCSP-122, 4
TDFN33-12
WLCSP-12
2.0
0.88
50
114
W
°C/W
1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions other than the operating conditions
specified is not implied. Only one Absolute Maximum Rating should be applied at any one time.
2. Mounted on FR4 board; for the WLCSP package, use the NSMD (none-solder mask defined) pad style for tighter control on the copper etch process.
3. Derate 20mW/°C above 25°C ambient.
4. Derate 8.8mW/°C above 25°C ambient.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
201999B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 20, 2013
3
DATA SHEET
AAT1171
600mA Voltage-Scaling Step-Down Converter
for RF Power Amplifiers with Bypass Switch
Electrical Characteristics1
TA = -40°C to +85°C, unless otherwise noted. VIN = VCC = 3.6V; typical values are TA = 25°C.
Symbol
VIN
VUVLO
VOUT
VDACIN
Description
Input Voltage
UVLO Threshold
UVLO Hysteresis
VOUT Programmable Range
Input Voltage Range from DAC
IQ
Quiescent Current
ISHDN
Shutdown Current
ILIM
P-Channel Current Limit
RDS(ON)H
High Side Switch On Resistance
RDS(ON)L
Low Side Switch On Resistance
RDS(ON)BP
Bypass Switch Resistance
ILXLEAK
LX Leakage Current
∆VOUT/
Load Regulation
VOUT
∆VOUT/
Line Regulation
VOUT/∆VIN
ROUT
Feedback Impedance
VOUT
Output Voltage Accuracy
FOSC
Oscillator Frequency
TSD
Over-Temperature Shutdown Threshold
THYS
Over-Temperature Shutdown Hysteresis
ILL
Light Load Load Current Threshold
tVOUTS
Output Voltage Settling Time
PWM/Light Load/EN
Enable Threshold Low
VEN(L)
VEN(H)
Enable Threshold High
IEN
Input Low Current
tEN
Turn-On Enable Response Time
MODE/SYNC
FMODE/SYNC Synchronization Frequency
VMODE/
MODE/SYNC High Level Threshold
Conditions
SYNC(L)
Typ
2.7
VIN Rising
No Load, Light Load
No Load, PWM, VCC Bias Current
EN = AGND = PGND, MODE/SYNC = VIN or
GND
TA = 25°C
45
420
1.2
VDAC = 1.3V or BYPASS = VIN
VCC = 5.5V, VLX = 0 to VCC, EN = 0V
1.746
170
1.8
2.0
140
15
100
VOUT = 0.6V to VOUT(MAX), MODE/SYNC = VIN
5.5
V
V
mV
V
V
3.6
1.2
70
μA
1
A
mΩ
mΩ
mΩ
μA
0.5
%
0.2
%/V
1.854
0.6
VCC = 5.5V
AAT1171-1: EN = Low to High, MODE/SYNC
= High, VDAC = 1.2V
AAT1171-4/AAT1171-5: EN = Low to High,
MODE/SYNC = High, VDAC = 1.2V
1.4
-1.0
1.0
kΩ
V
MHz
°C
°C
mA
μs
V
V
μA
150
μs
50
Sync to 19.8MHz2
19.8
MHz
VIN0.4
VSYNC = GND or VCC
μA
1.0
30
V
MODE/SYNC Low Level Threshold
IMODE/SYNC MODE/SYNC Low Current
DAC Input
Gain
Output Voltage/DAC Voltage3
Units
1.6
230
230
85
ILOAD = 0 to 500mA
VDAC = 0.6V, ILOAD = 0
Max
2.6
200
0.6
0.2
SYNC(H)
VMODE/
Min
-1.0
0.4
V
1.0
μA
3
V/V
1. The AAT1171 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.
2. Please contact Sales for other synchronization frequencies.
3. Please contact Sales for other output voltage/DAC voltage gains.
4
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
201999B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 20, 2013
DATA SHEET
AAT1171
600mA Voltage-Scaling Step-Down Converter
for RF Power Amplifiers with Bypass Switch
Typical Characteristics
Efficiency vs. Output Current
Load Regulation
(LL Mode; VOUT = 3.3V)
(LL Mode; VOUT = 3.3V)
100
Output Voltage Error (%)
Efficiency (%)
90
1.0
VIN = 3.9V
80
VIN = 4.2V
70
VIN = 5.0V
60
50
40
0.1
1
10
100
1000
0.5
VIN = 5.0V
0.0
VIN = 3.6V
VIN = 4.2V
-0.5
-1.0
0.1
1
10
Output Current (mA)
Efficiency vs. Output Current
Load Regulation
(PWM Mode; VOUT = 3.3V)
(PWM Mode; VOUT = 3.3V)
1.0
Output Voltage Error (%)
90
Efficiency (%)
80
70
VIN = 4.2V
VIN = 3.6V
60
50
40
VIN = 5.0V
30
20
10
0.1
1
10
100
1000
VIN = 5.0V
0.5
0.0
VIN = 3.6V
-0.5
-1.0
0.1
VIN = 4.2V
1
10
Output Current (mA)
100
1000
Output Current (mA)
Efficiency vs. Output Current
Load Regulation
(LL Mode; VOUT = 2.5V)
(LL Mode; VOUT = 2.5V)
1.0
Output Voltage Error (%)
100
VIN = 3.0V
90
Efficiency (%)
1000
Output Current (mA)
100
0
100
80
VIN = 4.2V
70
VIN = 5.0V
60
50
40
0.1
1
10
Output Current (mA)
100
1000
0.5
VIN = 5.0V
VIN = 4.2V
0.0
VIN = 3.0V
-0.5
-1.0
0.1
1
10
100
1000
Output Current (mA)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
201999B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 20, 2013
5
DATA SHEET
AAT1171
600mA Voltage-Scaling Step-Down Converter
for RF Power Amplifiers with Bypass Switch
Typical Characteristics
Efficiency vs. Output Current
Load Regulation
(PWM Mode; VOUT = 2.5V)
(PWM Mode; VOUT = 2.5V)
1.0
Output Voltage Error (%)
100
90
Efficiency (%)
80
VIN = 3.0V
70
60
VIN = 4.2V
50
40
30
VIN = 5.0V
20
10
0
0.1
1
10
100
1000
VIN = 5.0V
0.5
VIN = 3.0V
0.0
VIN = 4.2V
-0.5
-1.0
0.1
1
Output Current (mA)
Efficiency vs. Output Current
Load Regulation
(LL Mode; VOUT = 1.8V)
(LL Mode; VOUT = 1.8V)
Output Voltage Error (%)
Efficiency (%)
VIN = 2.7V
80
VIN = 4.2V
70
60
VIN = 3.6V
50
40
30
0.1
1
10
100
1000
VIN = 3.6V
0.5
VIN = 4.2V
0.0
VIN = 2.7V
-0.5
-1.0
0
1
Load Regulation
(PWM Mode; VOUT = 1.8V)
(PWM Mode; VOUT = 1.8V)
Efficiency (%)
Output Voltage Error (%)
VIN = 2.7V
80
70
VIN = 3.6V
60
50
40
VIN = 4.2V
30
20
10
1
10
Output Current (mA)
6
100
1000
Output Current (mA)
100
0.1
10
Efficiency vs. Output Current
90
1000
1.0
Output Current (mA)
0
100
Output Current (mA)
100
90
10
100
1000.
1.0
VIN = 3.6V
0.5
VIN = 4.2V
0.0
VIN = 2.7V
-0.5
-1.0
0.1
1
10
100
Output Current (mA)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
201999B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 20, 2013
1000
DATA SHEET
AAT1171
600mA Voltage-Scaling Step-Down Converter
for RF Power Amplifiers with Bypass Switch
Typical Characteristics
Output Voltage vs. Supply Voltage
Output Voltage vs. Supply Voltage
(LL Mode; VOUT = 1.5V)
(PWM Mode; VOUT = 1.5V)
1.514
1.510
Output Voltage (V)
Output Voltage (V)
1.514
IOUT = 50mA
1.506
IOUT = 300mA
1.502
1.498
IOUT = 600mA
1.494
2.7 2.9 3.1 3.3 3..5 3.7 3..9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
1.510
IOUT = 50mA
1.506
IOUT = 300mA
1.502
IOUT = 600mA
1.498
1.494
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
Supply Voltage (V)
Supply Voltage (V)
Output Voltage vs. Temperature
Bypass Mode Dropout Voltage
vs. Load Current
0.05
1.0
Dropout Voltage (V)
Output Voltage Error (%)
(VIN = 3.6V; VOUT = 1.8V; VDAC = 0.6V; RL = 10)
0.5
0.0
-0.5
-1.0
-1.5
-40
-15
10
35
60
0.00
-0.05
-0.10
-0.15
-0.20
-0.25
-0.30
0.1
85
1
10
Temperature (°°C)
1000
Load Current (mA)
Supply Current vs. Supply Voltage
Supply Current vs. Supply Voltage
(No Load; LL Mode)
(No Load; PWM Mode)
7.0
70
65
Supply Current (mA)
Supply Current (µA)
100
VOUT = 1.8V
60
55
50
45
VOUT = 0.6V
40
35
30
6.5
VOUT = 1.8V
6.0
5.5
5.0
4.5
4.0
3.5
VOUT = 0.6V
3.0
2.5
2.0
2.7
3.1
3.5
3.9
4.3
Supply Voltage (V)
4.7
5.1
5.5
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Supply Voltage (V)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
201999B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 20, 2013
7
DATA SHEET
AAT1171
600mA Voltage-Scaling Step-Down Converter
for RF Power Amplifiers with Bypass Switch
Typical Characteristics
P-Channel RDS(ON) vs. Input Voltage
Bypass RDS(ON) vs. Input Voltage
140
400
TJ = 120°C
TJ = 85°C
300
250
TJ = 25°C
200
TJ = 120°C
120
RDS(ON) (mΩ
Ω)
RDS(ON) (mΩ
Ω)
350
150
100
100
80
TJ = 25°C
60
40
20
50
0
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1
0
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
4.3 4.5 4.7 4.9 5.1 5.3 5.5
Input Voltage (V)
Input Voltage (V)
Switching Frequency vs. Temperature
Output Voltage vs. DAC Voltage
(VIN = 3.6V; VOUT = 1.8V; RL = 10)
(VIN = 4.2V; LL Mode)
2.06
4.5
2.04
4.0
2.02
Output Voltage (V)
Switching Frequency (MHz)
TJ = 85°C
PWM
2.00
1.98
LL
1.96
1.94
1.92
1.90
-40.0
-20.0
0.0
20.0
40.0
60.0
80.0
Temperature (°°C)
25°C
3.5
85°C
3.0
2.5
2.0
-40°C
1.5
1.0
0.5
0.0
0.2
0.4
0.6
0.8
1.0
DAC Voltage (V)
Heavy Load Switching Waveform
(VIN = 3.6V; VOUT = 1.8V; RL = 3Ω; COUT = 4.7µF; L = 2.2µH)
VOUT
(AC coupled)
20mV/div
IL
200mA/div
0
VLX
2V/div
0
Time (200ns/div)
8
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
201999B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 20, 2013
1.2
1.4
DATA SHEET
AAT1171
600mA Voltage-Scaling Step-Down Converter
for RF Power Amplifiers with Bypass Switch
Typical Characteristics
Light Load Switching Waveform
Light Load Switching Waveform
(PWM Mode; VIN = 4.2V; VOUT = 0.6V; RL = 10Ω;
COUT = 4.7µF; L = 2.2µH)
(LL Mode; VIN = 4.2V; VOUT = 0.6V; RL = 10Ω;
COUT = 4.7µF; L = 2.2µH)
VOUT
(AC coupled)
20mV/div
VOUT
(AC coupled)
20mV/div
IL
100mA/div
IL
200mA/div
VLX
2V/div
VLX
2V/div
0
0
0
0
Time (200ns/div)
Time (1µs/div)
DAC Transient Response in PWM Mode
DAC Transient Response in LL Mode
(VIN = 3.6V; RL = 10Ω; COUT = 4.7µF; L = 2.2µH)
(VIN = 3.6V; RL = 10Ω; COUT = 4.7µF; L = 2.2µH)
VOUT
1V/div
3.3V
VOUT
1V/div
3.3V
0.6V
0.6V
0
0
1.2V
1.2V
VDAC
0.5V/div
VDAC
0.5V/div
0.2V
0
0.2V
0
Time (25µs/div)
Time (25µs/div)
Bypass Transient Response
Bypass Transient Response
(PWM Mode; VIN = 3.6V; RL = 10Ω; COUT = 4.7µF; L = 2.2µH)
(LL Mode; VIN = 3.6V; RL = 10Ω; COUT = 4.7µF; L = 2.2µH)
3.5V
VOUT
1V/div
3.5V
VOUT
1V/div
0.6V
0.6V
0
0
VBYP
1V/div
VBYP
1V/div
0
0
Time (25µs/div)
Time (25µs/div)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
201999B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 20, 2013
9
DATA SHEET
AAT1171
600mA Voltage-Scaling Step-Down Converter
for RF Power Amplifiers with Bypass Switch
Typical Characteristics
DAC to Bypass Transient Response
Enable Soft Start
(LL Mode; VIN = 4.2V; RL = 10Ω; COUT = 4.7µF; L = 2.2µH)
(VIN = 3.6V; VOUT = 1.8V; RL = 3.9Ω;
COUT = 4.7µF; L = 2.2µH)
4.2V
VOUT
1V/div
1.8V
0V
VOUT
1V/div
Enable
2V/div
0.6V
0
1.3V
VDAC
0.5V/div
IIN
200mA/div
0.2V
0
0V
0A
Time (20µs/div)
Time (25µs/div)
Load Transient Response
Load Transient Response
(VIN = 4.2V; VOUT = 3.3V; COUT = 4.7µF; L = 2.2µH)
(VIN = 3.6V; VOUT = 1.8V; COUT = 4.7µF; L = 2.2µH)
VOUT
(AC coupled)
20mV/div
VOUT
(AC coupled)
20mV/div
3.51V
1.914V
3.26V
1.798V
500mA
525mA
IOUT
200mA/div
IOUT
100mA/div
250mA
Time (20µs/div)
200mA
Time (20µs/div)
Line Transient Response
(VOUT = 1.5V; RL = 10Ω
Ω; COUT = 4.7µF; L = 2.2µH)
VIN
0.5V/div
3.6V
3.0V
1.56V
VOUT
(AC coupled)
50mV/div
1.44V
Time (50µs/div)
10
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
201999B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 20, 2013
DATA SHEET
AAT1171
600mA Voltage-Scaling Step-Down Converter
for RF Power Amplifiers with Bypass Switch
Functional Block Diagram
VOUT
VCC
VIN
Comp
DH
Error
Amp
DAC
Logic
LX
EN
DL
BYPASS
MODE/SYNC
MODE/SYNC
Interface
AGND
Functional Description
The AAT1171 is a 600mA 2MHz peak current mode synchronous step-down (buck) converter designed to operate from a single-cell lithium-ion battery with a 2.7V to
4.2V input range. The output voltage is dynamically
programmed by the DAC input voltage.
To maximize converter efficiency over all load conditions,
the converter automatically transitions to a variable frequency light load (LL) mode when the load is less than
100mA. When combined with the very low quiescent
current, the LL mode maintains a high efficiency over the
complete load range. For noise sensitive applications,
the converter can be forced into a fixed frequency PWM
mode. Provisions are also made for synchronization of
the converter to an external system clock.
The synchronous buck converter power output devices
are sized at 230mΩ for a 600mA full load output current.
PGND
In addition to the converter output, an additional low
resistance bypass MOSFET (85mΩ) can be connected
between the battery input and the converter output (VIN
to VOUT), bypassing the converter and output inductor to
improve headroom and extend the WCDMA PA full power
range. This reduces the battery voltage necessary for a
WCDMA RF power amplifier to meet linearity requirements, thus extending operating time. In dual mode
systems, the bypass mode may also be used when the
WCDMA RF power amplifier is in GSM mode. Bypass
mode is activated by setting the bypass input high or by
forcing the baseband DAC output voltage to 1.3V.
The AAT1171 requires only three external components
for operation (CIN, COUT, LX). The high 2MHz switching
frequency reduces the inductor size required to 2.2μH
for the AAT1171-1/AAT1171-4 and 4.7μH for the
AAT1171-5. This reduces the DC resistance and improves
the converter efficiency while minimizing the inductor
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11
DATA SHEET
AAT1171
600mA Voltage-Scaling Step-Down Converter
for RF Power Amplifiers with Bypass Switch
footprint and height. The output voltage of the converter
is regulated to within 0.5% and will settle in less than
30μs (according to WCDMA specifications) in response to
any step change in the DAC input.
Under-voltage lockout, internal compensation, soft-start,
over-current, and over-temperature protection are also
included.
DAC Output Voltage Control
The output voltage is programmed by way of the DAC
input voltage. The DAC to output gain for the AAT1171
is 3.
VOUT = 3 · VDAC
The DAC input voltage range is 0.2V to 1.2V, which corresponds to an output voltage range of 0.6V to 3.6V (see
Figure 1). For a 1.3V DAC level, the bypass switch is
activated and the output voltage level is equivalent to
the input voltage minus the bypass MOSFET (RDS(ON)(bp))
drop.
Bypass Mode
In bypass mode, the AAT1171 bypasses the output
inductor, connecting the input directly to the output
through a low RDS(ON) 85mΩ MOSFET. Bypass mode is
initiated by applying 1.3V to the DAC input or by applying a logic high to the bypass input. When not activated,
a logic level low must be applied to the bypass input pin.
The bypass MOSFET current is limited to 600mA.
LL/PWM Control
Two control modes are available with the AAT1171: LL
mode and PWM mode. PWM mode maintains a fixed
switching frequency regardless of load. The fixed switching frequency gives the advantage of lower output ripple
and simplified output and input noise filtering. PWM
mode also provides a faster output voltage response to
changes in the DAC voltage.
In LL mode, the converter transitions to a variable
switching frequency as the load decreases below 100mA.
Above 100mA, where switching losses no longer dominate, the switching frequency is fixed. The LL mode’s
effect on the DAC to output voltage response time is
most notable when transitioning from a high output voltage to a low voltage. When the converter is in PWM
mode, the inductor current can be reversed and the output voltage actively discharged by the synchronous
MOSFET. While in LL mode, the output voltage is discharged by the load only, resulting in a slower response
to a DAC transition from a high to a low voltage.
For PWM mode, apply a logic level high to the MODE/
SYNC pin; for LL mode, apply a logic level low to the
MODE/SYNC pin.
Soft Start/Enable
The AAT1171 soft-start control prevents output voltage
overshoot and limits inrush current when either the input
power or the enable input is applied. When pulled low,
the enable input forces the converter into a low-power,
non-switching state with less than 1μA bias current.
V IN
4V
3V
BYPASS MODE
Output to PA
3.6V
2V
1V
0.6V
0.2V
1V
1.2V 1.3V
DAC Output
Figure 1: VOUT vs. VDAC.
12
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DATA SHEET
AAT1171
600mA Voltage-Scaling Step-Down Converter
for RF Power Amplifiers with Bypass Switch
Low Dropout Operation
For conditions where the input voltage drops to the output voltage level, the converter duty cycle increases to
100%. As 100% duty cycle is approached, the minimum
off-time initially forces the high-side on-time to exceed
the 2MHz clock period, reducing the converter switching
frequency. Once the input drops to the level where the
output can no longer be regulated, the high-side P-channel
MOSFET is enabled continuously for 100% duty cycle. The
output voltage then tracks the input voltage minus the IR
drop of the high side P-channel MOSFET RDS(ON).
UVLO Shutdown
Under-voltage lockout (UVLO) circuitry monitors the input
voltage and disables the converter when the input voltage
drops to 2.4V, guaranteeing sufficient operating input
voltage to maintain output voltage regulation and control.
For a rising input voltage, the UVLO circuitry enables the
converter 200mV above the shutdown level at 2.6V.
Current Limit and
Short-Circuit Protection
The high-side P-channel MOSFET current limit comparator limits the peak inductor current to 1.6A. In PWM
mode, the synchronous MOSFET current limit comparator limits the peak negative inductor current, and output
capacitor discharge current is limited to 1A. In bypass
mode, the bypass MOSFET current is limited to 600mA.
In the event of an overload or short-circuit condition, the
current limit protects the load and the AAT1171 power
devices. Upon removal of the short-circuit or fault condition, the AAT1171 output automatically recovers to the
regulated level.
Thermal Overload Protection
The maximum junction temperature is limited by the
AAT1171 over-temperature shutdown protection circuitry. Both the step-down converter and the bypass
MOSFET are disabled when the junction temperature
reaches 140°C. Normal operation resumes once the
junction temperature drops to 125°C.
External Synchronization
The AAT1171 switching frequency can be synchronized to
an external square wave clock via the MODE/SYNC input.
The external clock frequency range and logic levels for
which the AAT1171 will remain synchronized are listed in
the Electrical Characteristics table of this datasheet.
Applications Information
Inductor Selection
The step-down converter uses peak current mode control with slope compensation to maintain stability for
duty cycles greater than 50%. Because the required
slope compensation varies with output voltage, the
AAT1171 varies the slope compensation to match the
output voltage. This allows the use of a single inductor
value for all output voltage levels. The inductor value is
2.2μH for the AAT1171-1/AAT1171-4 and 4.7μH for the
AAT1171-5.
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. The inductor ripple current varies with both the input voltage and the output
voltage and peaks at the maximum input voltage with
the output at one half of the input voltage. For the typical AAT1171, this corresponds to a 4.2V input voltage
and a 2.1V output voltage. With the suggested 2.2μH
inductor, this corresponds to 239mA peak-to-peak ripple
current. For a 600mA DC load current, the peak inductor
current would be 718mA. In order to prevent saturation
under normal load conditions, the peak inductor current
should be less than the inductor saturation current.
IPK(MAX) = IO +
VIN(MAX)
8 ∙ L ∙ FS
= 0.6A +
4.2V
8 ∙ 2.2μH ∙ 2MHz
= 0.6A + 0.12A
= 0.72A
Some inductors may meet peak and average current
requirements 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 inductor losses can be estimated by using the full load output current. The output
inductor losses can then be calculated to estimate their
effect on overall device efficiency.
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13
DATA SHEET
AAT1171
600mA Voltage-Scaling Step-Down Converter
for RF Power Amplifiers with Bypass Switch
PL = IO2 ⋅ DCR = 0.6A2 ⋅ 0.14Ω = 50mW
PO
3.4 ⋅ 0.6A
η=
=
= 97%
PO + PL 3.4V ⋅ 0.6A + 50mW
The 2.2μH inductor selected for the AAT1171 evaluation
board has a 140mΩ DCR and a 0.91A DC current rating.
At 600mA load current, the inductor loss is 50mW which
gives 2.4% loss in efficiency for a 600mA 3.4V output
voltage with an inductor that measures 3.2x3.2x1.2mm.
Output Capacitor Selection
Input Capacitor Selection
A 10V X5R or X7R ceramic capacitor is suggested for the
input capacitor with typical values ranging from 4.7μF to
10μF. To estimate the required input capacitance size,
determine the acceptable input ripple level (VPP) and solve
for C, as shown below. The calculated value varies with
input voltage and is a maximum when VIN is double the
output voltage. Always examine the ceramic capacitor DC
voltage coefficient characteristics when selecting the
proper value. For example, due to the voltage coefficient
of a 10μF 6.3V X5R ceramic capacitor, with an applied
voltage of 5V DC the capacitance decreases to 6μF.
The AAT1171-1/AAT1171-4 are designed for use with
4.7μF 10V X5R ceramic output capacitors, while the
AAT1171-5 is designed for use with 10μF 10V X5R
ceramic output capacitors. Although a larger output
capacitor provides improved response to large load transients, it also limits the output voltage rise and fall time
in response to the DAC input. For stable operation, with
sufficient phase and gain margin, the internal voltage
loop compensation limits the minimum output capacitor
value to 4.7μF. Increased output capacitance will reduce
the crossover frequency with greater phase margin.
The output voltage droop due to load transients is dominated by the output capacitor. During a step increase in
load current, the output capacitor supplies the load current while the control loop responds. Within two or three
switching cycles, 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 · ∆ILOAD
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 output capacitor
value necessary to meet a given output voltage droop
requirement (VDROOP) for a given load transient.
CIN =
1
2· 3
·
VOUT · (VIN(MAX) - VOUT)
L · FS · VIN(MAX)
Dissipation due to the RMS current in the ceramic output
capacitor ESR is typically minimal, resulting in less than
a few degrees rise in hot-spot temperature.
14
⎛ VPP
⎞
- ESR · FS
⎝ IO
⎠
VO ⎛
V ⎞
1
· 1- O =
VIN ⎝
VIN ⎠
4
CIN(MIN) =
1
⎛ VPP
⎞
- ESR · 4 · FS
⎝ IO
⎠
The maximum input capacitor RMS current is:
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) =
The maximum output capacitor RMS ripple current is:
IRMS(MAX) =
V ⎞
VO ⎛
· 1- O
VIN ⎝
VIN ⎠
VO
IO
2
⎛
V ⎞
· 1- O
The term VIN ⎝ VIN ⎠ appears in both the input voltage
ripple and input capacitor RMS current equations and is
a maximum when VIN is twice Vo; therefore, the input
voltage ripple and the input capacitor RMS current ripple
are a maximum at 50% duty cycle.
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DATA SHEET
AAT1171
600mA Voltage-Scaling Step-Down Converter
for RF Power Amplifiers with Bypass Switch
The input capacitor provides a low impedance loop for
the edges of pulsed current drawn by the AAT1171. 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 layout in Figure 4.
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 with errors in loop phase and gain
measurements.
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 (C3 of Figure 5) should be
placed in parallel with the low ESR, ESL bypass ceramic
capacitor. This dampens the high Q network and stabilizes the system.
DAC Programming Gain
The output voltage is dynamically controlled by the DAC
input voltage. The DAC to output gain is fixed at 3. The
typical response time for a 0.2V to 1.2V pulsed signal on
the DAC input is less than 30μs. The DAC gain can be
reduced by an external resistive divider at the DAC
input, as shown in the evaluation board schematic in
Figures 2 and 3. For a DAC to output gain of 2 and R2
at 10kΩ, R1 is 4.99kΩ.
R1 =
Thermal Calculations
There are three types of losses associated with the
AAT1171 step-down converter: switching losses, conduction losses, and quiescent current losses. Conduction
losses are associated with the RDS(ON) characteristics of
the power MOSFET devices. Switching losses are dominated by the gate charge of the power MOSFET devices.
The AAT1171 main and synchronous power MOSFETs are
sized to have similar RDS(ON) values that track with the
input voltage. At full load, assuming continuous conduction mode (CCM), a simplified form of the step-down
converter losses is given by:
PTOTAL = IO2 · RDS(ON) + (tSW · FS · IO + IQ) · VIN
IQ is the step-down converter quiescent current. The
term tsw is used to estimate the full load switching losses, which are dominated by the gate charge losses.
For the condition where the buck converter is at 100%
duty cycle dropout, the total device dissipation reduces
to:
PTOTAL = IO2 · RDS(ON) + IQ · VIN
In bypass mode, the bypass MOSFET RDS(ON)(bp) is used to
determine the losses. The power MOSFET RDS(ON) increases with decreasing input voltage and the associated
losses are a maximum at the minimum input voltage
(2.7V).
PTOTAL = IO2 · RDS(ON)(bp) + IQ · VIN
Since the RDS(ON), quiescent current, and switching losses
all vary with input voltage, the total losses should be
investigated over the complete input voltage range.
After calculating the total losses, the maximum junction
temperature can be derived from the θJA for the TDFN3312 package which is typically 50°C/W.
TJ(MAX) = PTOTAL · ΘJA + TAMB
(3- GDAC)R2
(3 - 2)10kΩ
=
= 4.99kΩ
GDAC
2
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15
DATA SHEET
AAT1171
600mA Voltage-Scaling Step-Down Converter
for RF Power Amplifiers with Bypass Switch
U1
AAT1171-1/AAT1171-4
1
2
3
4
5
6
GND
DAC
R1
N/C
LX
PGND
VOUT
VIN
MODE/SYNC
AGND
BYPASS
DAC
12
VOUT
11
VOUT
VCC
L1
2.2μH
EN
C2
4.7μF
10
9
GND
C1
4.7μF
8
7
VIN
R2
1 2 3
ENABLE
Off On
3 2 1
1 2 3
BYPASS
SYNC
On Off LL PWM
Figure 2: AAT1171-1/AAT1171-4 Evaluation Board Schematic.
U2
AAT1171-5
1
2
3
4
5
6
GND
DAC
R1
N/C
L1
4.7μH
LX
PGND
VOUT
VIN
AGND
DAC
VOUT
11
VOUT
VCC
12
MODE/SYNC
BYPASS
EN
C2
10μF
10
9
C1
4.7μF
8
7
GND
VIN
R2
1 2 3
ENABLE
Off On
3 2 1
1 2 3
BYPASS
SYNC
On Off LL PWM
Figure 3: AAT1171-5 Evaluation Board Schematic.
16
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DATA SHEET
AAT1171
600mA Voltage-Scaling Step-Down Converter
for RF Power Amplifiers with Bypass Switch
WLCSP Package Light Sensitivity
The electrical performance of the WLCSP package can be
adversely affected by exposing the device to certain light
sources such as direct sunlight or a halogen lamp whose
wavelengths are red and infra-reds. However, fluorescent lighting has very little effect on the electrical performance of the WLCSP package.
3.
4.
Layout
The suggested PCB layout for the AAT1171 is shown in
Figures 4 and 5. The following guidelines should be used
to ensure a proper layout.
1.
2.
The input capacitor (C1) should connect as closely
as possible to VIN (Pin 10) and PGND (Pin 11).
C2 and L1 should be connected as closely as possible. The connection of L1 to the LX pin should be as
short as possible.
Figure 4: AAT1171 Evaluation Board
Top Side Layout.
5.
The PCB trace connected to VOUT (Pins 2 and 3) is
tied to the bypass path, as well as the feedback path
for the control loop. In bypass mode, the full load
current is delivered directly from the battery input;
therefore, this trace should be sufficient to handle
current up to the bypass current limit level.
The resistance of the trace from the load return to
PGND (Pin 11) should be kept to a minimum. This
minimizes any error in DC regulation due to differences in the potential of the internal signal ground
and the power ground.
For good thermal coupling, PCB vias are required
from the pad for the TDFN exposed paddle to the
ground plane. The via diameter should be 0.3mm to
0.33mm and positioned on a 1.2mm grid.
Figure 5: AAT1171 Evaluation Board
Bottom Side Layout.
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17
DATA SHEET
AAT1171
600mA Voltage-Scaling Step-Down Converter
for RF Power Amplifiers with Bypass Switch
PA Step-Down Converter Design Example
Specifications
VO(BUCK)
VIN
FS
TAMB
0.6V to 3.4V with RL =10Ω
2.7V to 4.2V (3.6V nominal)
2.0MHz
85°C
Output Inductor
L1 = 2.2μH
For Copper Electronics SD3112, 2.2μH, DCR = 140mΩ.
ΔIL1(MAX) =
⎛
VO ⎛
V ⎞
2.1V
2.1V⎞
⋅ 1- O =
⋅ 1= 239mA
L ⋅ FS ⎝ VIN ⎠ 2.2µH ⋅ 2.0MHz ⎝
4.2V⎠
The maximum inductor ripple current occurs at 50% duty cycle at the maximum input voltage.
IPKL1 = IO +
ΔIL1(MAX)
= 0.6A + 0.118A = 0.718A
2
PL1 = IO2 ⋅ DCR = 0.6A2 ⋅ 140mΩ = 50mW
Output Capacitor
Specify that VDROOP = 0.2V for a 600mA load pulse.
COUT =
IRMS =
3 · ΔILOAD
3 · 0.6A
=
= 4.5µF
VDROOP · FS
0.2V · 2.0MHz
1
2· 3
·
(VO) · (VIN(MAX) - VO)
1
3.4V · (4.2V - 3.4V)
·
= 69mArms
=
L1 · FS · VIN(MAX)
2 · 3 4.7µH · 2.0MHz · 4.2V
PESR = ESR · IRMS2 = 5mΩ · (69mA)2 = 24µW
Input Capacitor
Specify a maximum input voltage ripple of VPP = 25mV.
CIN(MIN) =
IRMS =
1
1
=
= 3.4µF
⎛ VPP
⎞
⎛ 25mV
⎞
- 5mΩ · 4 · 2.0MHz
- ESR · 4 · FS
⎝ IO
⎠
⎝ 0.6A
⎠
IO
= 0.3Arms
2
P = ESR · IRMS2 = 5mΩ · (0.3A)2 = 0.45mW
18
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DATA SHEET
AAT1171
600mA Voltage-Scaling Step-Down Converter
for RF Power Amplifiers with Bypass Switch
AAT1171 Losses
PTOTAL = IO2 · RDS(ON) + (tsw · FS · IO + IQ) · VIN
= 0.62 · 0.29Ω + (5ns · 2.0MHz · 0.6A + 60µA) · 4.2V = 104mW
TJ(MAX) = PTOTAL · ΘJA + TAMB = 104mW · 50°C/W = 5.2°C + 70°C = 75.2°C
AAT1171 Dropout Losses
PTOTAL = IO2 · RDS(ON)(HS) + IQ · VIN
= 0.62 · 310mΩ + 100µA · 3.5V = 112mW
TJ(MAX) = PTOTAL · ΘJA + TAMB = 112mW · 50°C/W = 5.6°C + 70°C = 75.6°C
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
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19
DATA SHEET
AAT1171
600mA Voltage-Scaling Step-Down Converter
for RF Power Amplifiers with Bypass Switch
Manufacturer
Value
AVX
www.avxcorp.com
10μF
Murata
www.murata.com
4.7μF
TDK
www.tdk.com
4.7μF
10μF
10μF
Device
Voltage
Case Size
Part Number
Output Capacitor
10V
0805
0805ZD106KAT
Output or Input Capacitor
Input Capacitor
Output Capacitor
Output or Input Capacitor
Input Capacitor
Output Capacitor
Output or Input Capacitor
Input Capacitor
10V
6.3V
10V
10V
6.3V
10V
10V
6.3V
0805
0603
0805
0805
0603
0805
0805
0603
GRM21BR61A475KA73L
GRM188R60J475KE19D
GRM21BR61A106K
C2012X5R1A475K
C1608X5ROJ475K
C2012X5R1A106K
LMK212BJ475MG
JMK107BJ475MA
Taiyo Yuden
www.t-yuden.com
4.7μF
Manufacturer
Value
ISAT
IRMS
DCR
Case Size
(mm)
Part Number
Cooper Electronics
www.cooperet.com
2.2μH
4.7μH
2.2μH
4.7μH
2.2μH
2.2μH
1.12A
0.8A
1.1A
0.75A
0.91A
0.74A
1.3A
0.85A
0.52A
0.55A
140mΩ
246mΩ
96mΩ
238mΩ
200mΩ
110mΩ
3.1x3.1x1.2
3.1x3.1x1.2
3.2x3.2x1.2
3.2x3.2x1.2
2.0x2.0x1.0
2.0x2.0x1.4
SD3118-2R2
SD3112-4R7-R
CDRH2D11/HP
CDRH2D11/HP
LPF2010-2R2M
LPF2010-2R2M
Sumida
www.sumida.com
ABCO Electronics
www.abco.co.kr
Table 1: Suggested Component Selection.
20
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DATA SHEET
AAT1171
600mA Voltage-Scaling Step-Down Converter
for RF Power Amplifiers with Bypass Switch
Ordering Information
Package
Marking1
Part Number (Tape and Reel)2
TDFN33-12
RXXYY
AAT1171IWP-1-T1
TDFN33-12
XCXYY
AAT1171IWP-4-T1
TDFN33-12
WLCSP-12
XDXYY
UGYW3
AAT1171IWP-5-T1
AAT1171IUP-1-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
TDFN33-12
Index Area
0.43 ± 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.
2.
3.
4.
XYY = assembly and date code.
Sample stock is generally held on part numbers listed in BOLD.
YW = data code (year, week) for WLCSP-12 package.
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.
WLCSP-12
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
201999B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 20, 2013
21
DATA SHEET
AAT1171
600mA Voltage-Scaling Step-Down Converter
for RF Power Amplifiers with Bypass Switch
1.535 ± 0.035
0.300
0.200
Line 1:
Part Code
Line 2:
Year Code and
Bi-Week Code
(laser marking)
0.100
1.500
0.250
0.300
0.500 BSC
ø 0.2 (Ref.)
Pin 1 indication
1.000
Bottom View
Top View
0.645 ± 0.085
0.310 ± 0.025
0.245 ± 0.025
0.330 ± 0.025
0.070 ± 0.035
2.235 ± 0.035
End View
Side View
All dimensions in millimeters.
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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
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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.
22
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • [email protected] • www.skyworksinc.com
201999B • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • March 20, 2013