Data Sheets - Skyworks Solutions, Inc.

DATA SHEET
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications
General Description
Features
The AAT3141 is a low noise, constant frequency charge
pump DC/DC converter that uses a tri-mode load switch
(1X), fractional (1.5X), and doubling (2X) conversion to
maximize efficiency for white LED applications. The device
produces current levels up to 30mA on each of its four
current source outputs to drive various arrangements of
LEDs from a 2.7V to 5.5V input. Outputs may be operated
individually or in parallel for driving higher-current LEDs.
A low external parts count (two 1µF flying capacitors and
two small 1µF capacitors at VIN and CP) make the AAT3141
ideally suited for small battery-powered applications.
•VIN Range: 2.7V to 5.5V
• Tri-Mode 1X, 1.5X, and 2X Charge Pump for Maximum
Efficiency and VF Coverage
• Drives Low-VF and High-VF Type LEDs
• Up to Four 30mA Outputs
•AS2Cwire Independent 3+1 Output Addressing
• 32-Position Logarithmic Scale with Digital Control
• Low Noise Constant Frequency Operation
• 1MHz Switching Frequency
• AutoBias Technology
• Small Application Circuit
• Regulated Output Current
• Automatic Soft Start
• No Inductors
•IQ <1µA in Shutdown
• 12-Pin TSOPJW Package
The AAT3141 is equipped with Skyworks' unique
AutoBias™ technology which allows individual LEDs to be
powered either by charge pump or battery input, determined internally and automatically to maximize the
power efficiency even with a large difference in LED forward voltage.
Applications
Skyworks' Advanced Simple Serial Control™ (AS2Cwire™)
digital input is used to enable, disable, and set the LED
drive current with a 32-level logarithmic scale LED brightness control. The AAT3141 has a thermal management
system to protect the device in the event of a short-circuit
condition at an output pin. Built-in soft-start circuitry prevents excessive inrush current during start-up. A high
charge pump switching frequency enables the use of very
small external capacitors. In shutdown mode, the device
disconnects the load from VIN and reduces quiescent current to less than 1µA. The AAT3141 is available in the
very small, Pb-free 12-pin TSOPJW package.
• Color (RGB) Lighting
• Programmable Current Sources
• White LED Backlighting
• White Photo Flash for Digital Still Cameras
Typical Application
VIN
C1+
C1
1µF
C1C2+
CP
VBATTERY
C IN
1µF
C CP
1µF
AAT3141
C2
1µF
C2D1
D2
D3
D4
EN/SET
EN/SET
D4
D3
D2
D1
GND
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202140A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 6, 2012
1
DATA SHEET
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications
Pin Descriptions
Pin #
Symbol
1
2
3
4
5
6
7
8
9
10
11
12
C2+
CP
C1C1+
D3
D2
D4
D1
EN/SET
IN
GND
C2-
Function
Flying capacitor 2 positive terminal. Connect a 1µF capacitor between C2+ and C2-.
Charge pump output. Requires 1µF capacitor connected between this pin and ground.
Flying capacitor 1 negative terminal.
Flying capacitor 1 positive terminal. Connect a 1µF capacitor between C1+ and C1-.
Current source output #3.
Current source output #2.
Current source output #4.
Current source output #1.
AS2Cwire serial interface control pin.
Input power supply. Requires 1µF capacitor connected between this pin and ground.
Ground.
Flying capacitor 2 negative terminal.
Pin Configuration
TSOPJW-12
(Top View)
C2+
CP
C1C1+
D3
D2
2
1
12
2
11
3
10
4
9
5
8
6
7
C2GND
IN
EN/SET
D1
D4
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202140A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 6, 2012
DATA SHEET
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications
Absolute Maximum Ratings1
Symbol
VIN
Description
Input Voltage
EN/SET to GND Voltage
Maximum DC Output Current
Operating Junction Temperature Range
VEN/SET
IOUT2
TJ
Value
Units
-0.3 to 6
-0.3 to VIN + 0.3
150
-40 to 150
V
V
mA
°C
Value
Units
625
160
mW
°C/W
Thermal Information3
Symbol
PD
qJA
Description
Maximum Power Dissipation
Maximum Thermal Resistance
4
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. Based on long-term current density limitation.
3. Mounted on an FR4 board.
4. Derate 6.25mW/°C above 25°C.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202140A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 6, 2012
3
DATA SHEET
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications
Electrical Characteristics1
CIN = CCP = C1 = C2 = 1.0µF; TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = 25°C, VIN =
3.5V.
Symbol
Description
Conditions
Input Power Supply
VIN
Operation Range
Icc
Operating Current
ISHDN
Shutdown Current
IDX
Output Current Accuracy2
I(D-Match)
Current Matching3
hCP
Charge Pump Section Efficiency
Charge Pump Section
TSS
Soft-Start Time
FCLK
Clock Frequency
EN/SET
VEN(L)
Enable Threshold Low
VEN(H)
Enable Threshold High
TEN/SET LO
EN/SET Low Time
TEN/SET HI MIN Minimum EN/SET High Time
TEN/SET HI MAX Maximum EN/SET High Time
TOFF
EN/SET Off Timeout
TLAT
EN/SET Latch Timeout
IEN/SET
EN/SET Input Leakage
Min
Typ
Max
Units
5.5
V
µA
mA
µA
%
mA
%
%
2.7
VD1:D4 = 2.0V, CP = 1X
No Load Current, CP = 1.5X
VIN = 3.5V, EN/SET = 0
VIN = 3.5V, TA = 25°C
VIN = 3.5V, TA = 25°C, Code 28
VD1:D4 = 3.6V, VIN = 3.5V
VIN = 3.5V, IOUT(TOTAL) = 120mA, Measured from IN to CP
550
3
-10
17.1
-3
19
±0.5
93
5
1
10
20
3
50
1
VIN = 2.7V
VIN = 5.5V
µs
MHz
0.4
1.4
0.3
75
50
VEN/SET = 5.5V, VIN = 5.5V
-1
75
500
500
1
V
V
µs
ns
µs
µs
µs
µA
1. The AAT3141 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. Codes 2 through 7 are guaranteed to be within ±15% of stated current level.
3. Current matching is defined as I(D-Match) = (ID - IAVE)/IAVE.
4
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202140A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 6, 2012
DATA SHEET
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications
Typical Characteristics
Unless otherwise noted, VIN = 3.5V, CIN = CCP = C1 = C2 = 1µF, TA = 25°C.
Efficiency vs. Input Voltage
Efficiency vs. Input Voltage
(Code 26)
(D1 = 3.5V; D2 = 3.3V; D3 = 3.2V; D4 = 3.0V)
100
100
90
3.0VF
80
Efficiency (%)
Efficiency (%)
90
70
60
50
3.5VF
70
60
50
Code 28
40
40
30
Code 26
80
2.9
3.0
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
4.0
4.1
4.2
30
2.9
3.0
3.1
3.2
Code 32
3.3
3.4
3.5
3.6
3.7
3.8
3.9
4.0
4.1
4.2
Input Voltage (V)
Input Voltage (V)
Efficiency vs. Input Voltage
(D1-D2 = 3.5V; D3-D4 = 3.2V)
100
Efficiency (%)
90
Code 26
80
70
60
50
30
Code 32
Code 28
40
2.9
3.0
3.1
3.2
3.3
3.4
3.5
3.6
3.7
3.8
3.9
4.0
4.1
4.2
Input Voltage (V)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202140A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 6, 2012
5
DATA SHEET
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications
Typical Characteristics
Unless otherwise noted, VIN = 3.5V, CIN = CCP = C1 = C2 = 1µF, TA = 25°C.
Line Response
Line Response
(1X Mode, 4x19mA Load)
(1X Mode, 4x30mA Load)
VIN
(0.5V/div)
VIN
(0.5V/div)
VLED
(20mV/div)
VLED
(20mV/div)
VCP
(0.5V/div)
VCP
(0.5V/div)
ID
(10mA/div)
ID
(10mA/div)
Time (1ms/div)
Time (1ms/div)
Line Response
Turn-On to 1.5X Mode
(1.5X Mode, 4x19mA Load)
(4x30mA Load)
EN/SET
(2V/div)
VIN
(0.5V/div)
VCP
(4V/div)
VLED
(20mV/div)
VDIODE
(2V/div)
VCP
(0.5V/div)
IIN
(100mA/div)
ID
(10mA/div)
Time (1ms/div)
Time (100µs/div)
Load Characteristics
Load Characteristics
(1.5X Mode, 4x15mA Load)
(1.5X Mode, 4x30mA Load)
VF
(20mV/div)
VF
(20mV/div)
IIN
(10mA/div)
IIN
(10mA/div)
VCP
(20mV/div)
VCP
(20mV/div)
Time (1µs/div)
6
Time (1µs/div)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202140A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 6, 2012
DATA SHEET
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications
Typical Characteristics
Unless otherwise noted, VIN = 3.5V, CIN = CCP = C1 = C2 = 1µF, TA = 25°C.
Charge Pump to Load Switch
Charge Pump to Load Switch
(1.5X Mode, 4x19mA Load)
VIN
(500mV/div)
(1.5X Mode, 4x30mA Load)
VIN
(500mV/div)
VCP
(1V/div)
VDIODE
(500mV/div)
VCP
(1V/div)
VDIODE
(500mV/div)
IIN
(50mA/div)
IIN
(50mA/div)
Time (5ms/div)
Time (5ms/div)
Charge Pump to Load Switch
Charge Pump to Load Switch
(2X Mode, 4x19mA Load)
(2X Mode, 4x30mA Load)
VIN
(500mV/div)
VCP
(1V/div)
VIN
(500mV/div)
VCP
(1V/div)
VDIODE
(500mV/div)
VDIODE
(500mV/div)
IIN
(50mA/div)
IIN
(50mA/div)
Time (5ms/div)
Time (5ms/div)
Load Switch to Charge Pump
Load Switch to Charge Pump
(1.5X Mode, 4x19mA Load)
(1.5X Mode, 4x30mA Load)
VIN
(1V/div)
VIN
(1V/div)
VCP
(4V/div)
VCP
(4V/div)
VDIODE
(500mV/div)
VDIODE
(500mV/div)
IIN
(50mA/div)
IIN
(50mA/div)
Time (2ms/div)
Time (2ms/div)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202140A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 6, 2012
7
DATA SHEET
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications
Typical Characteristics
Unless otherwise noted, VIN = 3.5V, CIN = CCP = C1 = C2 = 1µF, TA = 25°C.
Turn-On to 1X Mode
Turn-On to 1X Mode
(4x19mA Load)
(4x30mA Load)
EN/SET
(2V/div)
EN/SET
(2V/div)
VCP
(4V/div)
VCP
(4V/div)
VDIODE
(2V/div)
VDIODE
(2V/div)
IIN
(100mA/div)
IIN
(100mA/div)
Time (100µs/div)
Time (100µs/div)
Turn-On to 1.5X Mode
Turn-On to 1.5X Mode
(4x19mA Load)
(4x30mA Load)
EN/SET
(2V/div)
EN/SET
(2V/div)
VCP
(4V/div)
VCP
(4V/div)
VDIODE
(2V/div)
VDIODE
(2V/div)
IIN
(100mA/div)
IIN
(100mA/div)
Time (100µs/div)
Time (100µs/div)
Turn-Off from Full-Scale 2X Mode
EN/SET
(2V/div)
VDIODE
(2V/div)
IIN
(200mA/div)
Time (100µs/div)
8
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202140A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 6, 2012
DATA SHEET
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications
Typical Characteristics
Unless otherwise noted, VIN = 3.5V, CIN = CCP = C1 = C2 = 1µF, TA = 25°C.
Input Current vs. Input Voltage
Input Current vs. Input Voltage
(4x10mA)
(4x30mA)
90
300
80
VDIODE = 3.4V
70
250
VDIODE = 3.4V
200
IIN (mA)
IIN (mA)
60
50
40
30
20
150
100
VDIODE = 3.0V
10
50
0
2.7
3.1
3.5
3.9
4.3
4.7
5.1
0
2.7
5.5
VDIODE = 3.0V
3.1
3.5
3.9
Input Voltage (V)
4.7
5.1
5.5
Input Voltage (V)
Diode Current vs. Input Voltage
VIH and VIL vs. VIN
(30mA, 15mA Settings)
0.850
40
0.825
35
IDIODE (mA)
4.3
0.800
VDIODE = 3.4V
0.775
30
VIH
0.750
0.725
25
VIL
0.700
20
0.675
VDIODE = 3.4V
15
0.650
0.625
0.600
10
2.7
3.1
3.5
3.9
4.3
Input Voltage (V)
4.7
5.1
5.5
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Input Voltage (V)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202140A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 6, 2012
9
DATA SHEET
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications
Functional Block Diagram
VIN
C1+
Soft-Start
Control
1X
1.5X
2X
Charge
Pump
1MHz
Oscillator
Voltage
Reference
EN/SET
C2+
C2CP
32 x 8 bit
ROM
AS2Cwire
Interface
C1-
32 x 8 bit
ROM
D/A
D1
D/A
D2
D/A
D3
D/A
D4
GND
Functional Description
AutoBias Technology
The AAT3141 is a tri-mode load switch (1X) and high
efficiency (1.5X or 2X) charge pump device intended for
white LED backlight applications. To maximize power
conversion efficiency, an internal sensing circuit monitors the voltage required on each constant current
source output and sets the load switch and charge pump
modes based on the input battery voltage and the current source output voltage. As the battery discharges
over time, the AAT3141 charge pump is enabled when
any of the four current source outputs nears dropout.
The charge pump initially starts in 1.5X mode. If the
charge pump output drops enough for any current
source output to become close to dropout, the charge
pump will automatically transition to 2X mode.
Each of the four current source outputs is independently
switched between the battery input (1X) or the charge
pump output (1.5X or 2X), depending on the voltage at
the current source output. Since the LED-to-LED forward
voltage (VF) can vary as much as 1V, this function significantly enhances overall device efficiency when the
battery input voltage level is greater than the voltage
required at any current source output.
10
The AAT3141 requires only four external components:
two 1µF ceramic capacitors for the charge pump flying
capacitors (C1 and C2), one 1µF ceramic input capacitor
(CIN), and one 0.33µF to 1µF ceramic charge pump output
capacitor (CCP). The four constant current outputs (D1 to
D4) drive four individual LEDs with a maximum current of
30mA each. The EN/SET AS2Cwire serial interface enables
the AAT3141 and sets the current source magnitudes.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202140A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 6, 2012
DATA SHEET
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications
Applications Information
Constant Current Output Level Settings
The constant current source amplitudes for D1 to D4 are
set via the serial interface according to a logarithmic scale
where each code is 1dB greater than the previous code.
In this manner, LED brightness appears linear with each
increasing code count. Because the outputs D1 to D4 are
true independent constant current sources, the voltage
observed on any single given output will be determined
by the actual forward voltage (VF) for the LED being
driven.
Since the output current of the AAT3141 is programmable, no PWM (pulse width modulation) or additional
control circuitry are needed to control LED brightness.
This feature greatly reduces the burden on a microcontroller or system IC to manage LED or display brightness, allowing the user to “set it and forget it.” With its
high-speed serial interface (1MHz data rate), the output
current of the AAT3141 can be changed successively to
brighten or dim LEDs in smooth transitions (e.g., to fade
out) or in abrupt steps, giving the user complete programmability and real-time control of LED brightness.
The individual current level settings are each approximately 1dB apart for settings above Code 8 (see Figure
1). The current level settings below Code 8 are more
than 1dB apart and serve the needs of transmissive displays and other low-current applications.
AS2Cwire Serial Interface
The current source output magnitude is controlled by the
AS2Cwire serial digital input. AS2Cwire adds addressing
capability for multiple data registers over the Simple
Serial Control™ (S2Cwire™), which is only capable of
controlling a single register. The AAT3141 has two registers. One contains the current level setting for outputs
D1 to D3, and the other contains the current level setting for output D4.
Current (mA)
1.00
0.10
0.01
0.00
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
Code
Figure 1: Normalized Current Level Settings.
Code
IOUT (typ)
(mA)
Code
IOUT (typ)
(mA)
Code
IOUT (typ)
(mA)
Code
IOUT (typ)
(mA)
1
2
3
4
5
6
7
8
0.0
0.1
0.2
0.4
0.5
0.7
1.1
1.8
9
10
11
12
13
14
15
16
2.0
2.2
2.5
2.8
3.2
3.5
4.0
4.5
17
18
19
20
21
22
23
24
5.1
5.6
6
7
8
9
10
12
25
26
27
28
29
30
31
32
13
15
17
19
21
24
27
30
Table 1: Constant Current Source Output Nominal Programming Levels.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202140A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 6, 2012
11
DATA SHEET
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications
Three addresses are used to control the two registers.
Address 0 addresses both registers simultaneously to
allow the loading of both registers with the same data
using a single write protocol. Address 1 addresses
Register 1 for D1 to D3 current level settings. Address 2
addresses Register 2 for D4 current level settings.
As with S2Cwire, AS2Cwire relies on the number of rising
edges of the EN/SET pin to address and load the registers. AS2Cwire latches data or address after the EN/SET
pin has been held high for time TLAT. Address or data is
differentiated by the number of EN/SET rising edges.
Since the data registers are 5 bits each, the differentiating number of pulses is 25 or 32, so that Address 0 is
signified by 33 rising edges, Address 1 by 34 rising
edges and Address 2 by 35 rising edges. Data is set to
any number of rising edges between 1 and including 32.
A typical write protocol is a burst of EN/SET rising edges,
signifying a particular address, followed by a pause with
EN/SET held high for the TLAT timeout period, a burst of
rising edges signifying data, and a TLAT timeout for the
data registers. Once an address is set, then multiple
writes to the corresponding data register are allowed.
Address 0 is the default address on the first rising edge
after the AAT3141 has been disabled. If data is presented on the first rising edge with no prior address,
both data registers are simultaneously loaded.
When EN/SET is held low for an amount of time greater
than TOFF, the AAT3141 enters into shutdown mode and
draws less than 1µA from VIN. Data and address registers
are reset to 0 during shutdown.
Address
EN/SET Rising Edges
Data Register
0
1
2
33
34
35
1 & 2: D1-D4
1: D1-D3
2: D4
Table 2: AS2Cwire Serial Interface Addressing.
LED Selection
The AAT3141 is specifically intended for driving white
LEDs. However, the device design will allow the AAT3141
to drive most types of LEDs with forward voltage specifications ranging from 1.0V to 4.3V. LED applications
may include main and sub-LCD display backlighting,
camera photo-flash applications, color (RGB) LEDs,
infrared (IR) diodes for remotes, and other loads benefiting from a controlled output current generated from a
varying input voltage. Since the D1 to D4 output current
sources are matched with negligible voltage dependence,
the LED brightness will be matched regardless of the
specific LED forward voltage (VF) levels.
In some instances (e.g., in high luminous output applications such as photo flash), it may be necessary to drive
high-VF type LEDs. The low-dropout current sources in
the AAT3141 make it capable of driving LEDs with forward voltages as high as 4.3V at full current from an
input supply as low as 3.0V. Outputs can be paralleled to
drive high-current LEDs without complication.
AS2Cwire Serial Interface Timing
Address
Data
THI
TLO
TLAT
TLAT
EN/SET
1
Address
12
2
33
34
1
0
2...
n <= 32
1
Data Reg 1
0
Data Reg 2
0
n
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202140A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 6, 2012
DATA SHEET
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications
Termination of Unused
Current Source Outputs
If any outputs (D1 to D4) are not used, they should be
terminated by connecting the respective unused output
directly to ground. This is required to assure correct
charge pump mode operation. If a given unused output
is not terminated to ground, it will appear to the respective output’s feedback control as an infinite impedance
load and the unused constant current source will be set
for a maximum voltage. Although no current flows from
the unused current source, the voltage sensed at that
node could force the charge pump control to activate the
charge pump when it is not necessary. To prevent this
effect, simply connect the unused constant current
source outputs to ground.
Device Switching Noise Performance
The AAT3141 operates at a fixed frequency of approximately 1MHz to control noise and limit harmonics that
can interfere with the RF operation of cellular telephone
handsets or other communication devices. Back-injected
noise appearing on the input pin of the charge pump is
20mV peak-to-peak, typically ten times less than inductor-based DC/DC boost converter white LED backlight
solutions. The AAT3141 soft-start feature prevents noise
transient effects associated with inrush currents during
start-up of the charge pump circuit.
to the device for a given LED current drive level. The
best white LED driver for a given application should be
based on trade-offs of size, external component count,
reliability, operating range, and total energy usage...not
just % efficiency.
The AAT3141 efficiency may be quantified under very
specific conditions and is dependent upon the input voltage versus the output voltage seen across the loads
applied to outputs D1 through D4 for a given constant
current setting. Depending upon the case of VIN being
greater than the specific voltage seen across the load on
D1 through D4, the device will operate in load switch
mode. If the voltage seen on the constant current source
output is less than VIN, then the device will operate in
1.5X or 2X charge pump mode. Each of these modes will
yield different efficiency values. Refer to the following
two sections for explanations of each operational mode.
Load Switch Mode Efficiency
The AAT3141 load switch mode is operational at all times
and functions alone to enhance device power conversion
efficiency when VIN is greater than voltage across the load
connected to the constant current source outputs. When
in load switch mode, the voltage conversion efficiency is
defined as output power divided by input power:
η=
Power Efficiency and Device Evaluation
The charge pump efficiency discussion in the following
sections only accounts for efficiency of the charge pump
section itself. Due to the unique circuit architecture and
design of the AAT3141, it is very difficult to measure
efficiency in terms of a percent value comparing input
power over output power.
Since the AAT3141 outputs are pure constant current
sources and typically drive individual loads, it is difficult
to measure the output voltage for a given output (D1 to
D4) to derive an overall output power measurement. For
any given application, white LED forward voltage levels
can differ, yet the output drive current will be maintained
as a constant.
This makes quantifying output power a difficult task
when taken in the context of comparing to other white
LED driver circuit topologies. A better way to quantify
total device efficiency is to observe the total input power
POUT
PIN
The expression to define the ideal efficiency (h) can be
rewritten as:
η=
POUT VOUT ∙ IOUT VOUT
=
=
PIN
VIN ∙ IOUT
VIN
-or-
η(%) = 100
 VOUT 
 VIN 
Charge Pump Section Efficiency
The AAT3141 contains a fractional charge pump which
will boost the input supply voltage when VIN is less than
the voltage required on the constant current source outputs. The efficiency (h) can be simply defined as a linear
voltage regulator with an effective output voltage that is
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13
DATA SHEET
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications
equal to one and one half or two times the input voltage.
Efficiency (h) for an ideal 1.5X charge pump can typically be expressed as the output power divided by the
input power:
η=
POUT
PIN
In addition, with an ideal 1.5X charge pump, the output
current may be expressed as 2/3 of the input current.
The expression to define the ideal efficiency (h) can be
rewritten as:
η=
POUT
VOUT ∙ IOUT
V
=
= OUT
PIN
VIN ∙ 1.5IOUT 1.5VIN
-or-
η(%) = 100
 VOUT 
 1.5VIN
For a charge pump with an output of 5V and a nominal
input of 3.5V, the theoretical efficiency is 95%. Due to
internal switching losses and IC quiescent current consumption, the actual efficiency can be measured at 93%.
These figures are in close agreement for output load
conditions from 1mA to 100mA. Efficiency will decrease
as load current drops below 0.05mA or when the level of
VIN approaches VOUT. Refer to the Typical Characteristics
section of this datasheet for measured plots of efficiency
versus input voltage and output load current for the
given charge pump output voltage options.
Capacitor Selection
Careful selection of the four external capacitors CIN, C1,
C2, and COUT is important because they will affect turn-on
time, output ripple, and transient performance. Optimum
performance will be obtained when low equivalent series
resistance (ESR) ceramic capacitors are used. In general, low ESR may be defined as less than 100mW. A value
of 1µF for all four capacitors is a good starting point
when choosing capacitors. If the LED current sources are
only programmed for light current levels, then the
capacitor size may be decreased.
Capacitor Characteristics
Ceramic composition capacitors are highly recommended over all other types of capacitors for use with the
AAT3141. Ceramic capacitors offer many advantages
over their tantalum and aluminum electrolytic counterparts. A ceramic capacitor typically has very low ESR, is
14
lowest cost, has a smaller PCB footprint, and is nonpolarized. Low ESR ceramic capacitors help maximize
charge pump transient response. Since ceramic capacitors are non-polarized, they are not prone to incorrect
connection damage.
Equivalent Series Resistance
ESR is an important characteristic to consider when
selecting a capacitor. ESR is a resistance internal to a
capacitor that is caused by the leads, internal connections, size or area, material composition, and ambient
temperature. Capacitor ESR is typically measured in milliohms for ceramic capacitors and can range to more
than several ohms for tantalum or aluminum electrolytic
capacitors.
Ceramic Capacitor Materials
Ceramic capacitors less than 0.1µF are typically made
from NPO or C0G materials. NPO and C0G materials
have tight tolerance and are stable over temperature.
Large capacitor values are composed of X7R, X5R, Z5U,
or Y5V dielectric materials. Large ceramic capacitors,
typically greater than 2.2µF, are often available in lowcost Y5V and Z5U dielectrics, but capacitors greater than
1µF are usually not required for AAT3141 applications.
Capacitor area is another contributor to ESR. Capacitors
that are physically large will have a lower ESR when
compared to an equivalent material smaller capacitor.
These larger devices can improve circuit transient
response when compared to an equal value capacitor in
a smaller package size.
Thermal Protection
The AAT3141 has a thermal protection circuit that will
shut down the charge pump if the die temperature rises
above the thermal limit, as is the case during a shortcircuit of the CP pin.
Charge Pump Compatibility
The four-output AAT3141 is pin-compatible with the
AAT3123, AAT3132, and AAT3113 in TSOPJW-12 packages. The AAT3141 offers an improved overall efficiency,
wider operating range, and the ability to drive high-VF
type LEDs at full current. The AAT3141 is well suited for
battery-powered applications using single-cell lithiumion/polymer batteries and 3-series connected dry cells
(3.6V).
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202140A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 6, 2012
DATA SHEET
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications
Ordering Information
Package
Marking1
Part Number (Tape and Reel)2
TSOPJW-12
LYXYY
AAT3141ITP-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
TSOPJW-12
2.85 ± 0.20
2.40 ± 0.10
0.20 + 0.10
- 0.05
0.50 BSC 0.50 BSC 0.50 BSC 0.50 BSC 0.50 BSC
7° NOM
0.055 ± 0.045
0.04 REF
0.15 ± 0.05
+ 0.10
1.00 - 0.065
0.9625 ± 0.0375
3.00 ± 0.10
4° ± 4°
0.45 ± 0.15
0.010
2.75 ± 0.25
All dimensions in millimeters.
1. XYY = assembly and date code.
2. Sample stock is generally held on all part numbers listed in BOLD.
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