AAT3141ITP-T1 [AAT]
High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications; 高效率1X / 1.5X / 2X电荷泵白光LED应用
| 型号： | AAT3141ITP-T1 |
| 厂家： | 
ADVANCED ANALOG TECHNOLOGY, INC. |
| 描述： | High Efficiency 1X/1.5X/2X Charge Pump for White LED Applications |
| 文件： | 总16页 (文件大小：494K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump
for White LED Applications
™
ChargePump
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 appli-
cations. 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. Alow external
parts count (two 1µF flying capacitors and two small
1µF capacitors at VIN and CP) make the AAT3141 ide-
ally 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
•
•
•
•
2
AS Cwire 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
The AAT3141 is equipped with AnalogicTech’s 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.
No Inductors
IQ <1µA in Shutdown
12-Pin TSOPJW Package
AnalogicTech's Advanced Simple Serial Control™
2
(AS Cwire™) digital input is used to enable, disable,
Applications
and set the LED drive current with a 32-level logarith-
mic 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
CP
C1+
C1
1μF
C1-
C2+
CIN
CCP
C2
VBATTERY
AAT3141
1μF
1μF
1μF
C2-
D1
D2
D3
D4
EN/SET
EN/SET
GND
D4
D3
D2
D1
3141.2007.03.1.3
1
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump
for White LED Applications
Pin Descriptions
Pin #
Symbol
Function
1
C2+
Flying capacitor 2 positive terminal. Connect a 1µF capacitor between C2+
and C2-.
2
CP
Charge pump output. Requires 1µF capacitor connected between this pin and
ground.
3
4
C1-
Flying capacitor 1 negative terminal.
C1+
Flying capacitor 1 positive terminal. Connect a 1µF capacitor between C1+
and C1-.
5
6
D3
D2
Current source output #3.
Current source output #2.
Current source output #4.
Current source output #1.
7
D4
8
D1
2
9
EN/SET
IN
AS Cwire serial interface control pin.
10
Input power supply. Requires 1µF capacitor connected between this pin and
ground.
11
12
GND
C2-
Ground.
Flying capacitor 2 negative terminal.
Pin Configuration
TSOPJW-12
(Top View)
1
2
3
4
5
6
12
11
10
9
C2+
CP
C1-
C1+
D3
C2-
GND
IN
EN/SET
D1
D4
8
7
D2
2
3141.2007.03.1.3
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump
for White LED Applications
1
Absolute Maximum Ratings
Symbol
Description
Value
Units
VIN
VEN/SET
IOUT
TJ
Input Voltage
EN/SET to GND Voltage
Maximum DC Output Current
Operating Junction Temperature Range
-0.3 to 6
-0.3 to VIN + 0.3
150
V
V
mA
°C
2
-40 to 150
3
Thermal Information
Symbol
Description
Maximum Power Dissipation
Maximum Thermal Resistance
Value
625
160
Units
mW
°C/W
4
PD
θJA
1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at condi-
tions 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.
3141.2007.03.1.3
3
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump
for White LED Applications
1
Electrical Characteristics
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
Min Typ Max Units
Input Power Supply
VIN
Operation Range
2.7
5.5
V
µA
mA
µA
%
VD1:D4 = 2.0V, CP = 1X
No Load Current, CP = 1.5X
VIN = 3.5V, EN/SET = 0
VIN = 3.5V, TA = 25°C
550
3
Icc
Operating Current
5
1
10
20
3
ISHDN
IDX
I(D-Match)
ηCP
Charge Pump Section
Shutdown Current
-10
2
Output Current Accuracy
VIN = 3.5V, TA = 25°C, Code 28 17.1 19
mA
%
3
Current Matching
VD1:D4 = 3.6V, VIN = 3.5V
-3
0.5
VIN = 3.5V, IOUT(TOTAL) = 120mA,
Charge Pump Section Efficiency
93
%
Measured from IN to CP
TSS
FCLK
Soft-Start Time
Clock Frequency
50
1
µs
MHz
EN/SET
VEN(L)
VEN(H)
TEN/SET LO
TEN/SET HI MIN Minimum EN/SET High Time
TEN/SET HI MAX Maximum EN/SET High Time
Enable Threshold Low
Enable Threshold High
EN/SET Low Time
VIN = 2.7V
VIN = 5.5V
0.4
75
V
V
1.4
0.3
µs
ns
µs
µs
µs
µA
50
75
500
500
1
TOFF
TLAT
IEN/SET
EN/SET Off Timeout
EN/SET Latch Timeout
EN/SET Input Leakage
VEN/SET = 5.5V, VIN = 5.5V
-1
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
3141.2007.03.1.3
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
(D1 = 3.5V; D2 = 3.3V; D3 = 3.2V; D4 = 3.0V)
Efficiency vs. Input Voltage
(Code 26)
100
90
80
70
60
50
40
30
100
90
80
70
60
50
40
30
Code 26
3.0VF
3.5VF
Code 32
Code 28
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
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)
Input Voltage (V)
Efficiency vs. Input Voltage
(D1-D2 = 3.5V; D3-D4 = 3.2V)
100
90
80
70
60
50
40
30
Code 26
Code 32
Code 28
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)
3141.2007.03.1.3
5
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
(1X Mode, 4x19mA Load)
Line Response
(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
(1.5X Mode, 4x19mA Load)
Line Response
(1.5X 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)
Load Characteristics
(1.5X Mode, 4x15mA Load)
Load Characteristics
(1.5X Mode, 4x30mA Load)
VF
(20mV/div)
VF
(20mV/div)
IIN
(10mA/div)
IIN
(10mA/div)
VCP
(20mV/div)
VCP
(20mV/div)
Time (1μμs/div)
Time (1μμs/div)
6
3141.2007.03.1.3
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
(1.5X Mode, 4x19mA Load)
Charge Pump to Load Switch
(1.5X Mode, 4x30mA Load)
VIN
(500mV/div)
VIN
(500mV/div)
VCP
(1V/div)
VCP
(1V/div)
VDIODE
(500mV/div)
VDIODE
(500mV/div)
IIN
(50mA/div)
IIN
(50mA/div)
Time (5ms/div)
Time (5ms/div)
Charge Pump to Load Switch
(2X Mode, 4x19mA Load)
Charge Pump to Load Switch
(2X Mode, 4x30mA Load)
VIN
(500mV/div)
VIN
(500mV/div)
VCP
(1V/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
(1.5X Mode, 4x19mA Load)
Load Switch to Charge Pump
(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)
3141.2007.03.1.3
7
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
(4x19mA Load)
Turn-On to 1X Mode
(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
(4x19mA Load)
Turn-On to 1.5X Mode
(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
3141.2007.03.1.3
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
(4x10mA)
Input Current vs. Input Voltage
(4x30mA)
90
80
70
60
50
40
30
20
10
0
300
250
200
150
100
50
VDIODE = 3.4V
VDIODE = 3.4V
VDIODE = 3.0V
VDIODE = 3.0V
0
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
Input Voltage (V)
Diode Current vs. Input Voltage
(30mA, 15mA Settings)
VIH and VIL vs. VIN
0.850
0.825
0.800
0.775
0.750
0.725
0.700
0.675
0.650
0.625
0.600
40
35
30
25
20
15
10
VDIODE = 3.4V
VIH
VIL
VDIODE = 3.4V
2.5
3.0
3.5
4.0
4.5
5.0
5.5
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
Input Voltage (V)
3141.2007.03.1.3
9
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump
for White LED Applications
Functional Block Diagram
VIN
Soft-Start
Control
C1+
C1-
1X
1.5X
2X
Charge
Pump
1MHz
Oscillator
C2+
C2-
Voltage
Reference
CP
32 x 8 bit
ROM
D/A
D/A
D/A
D/A
D1
D2
D3
D4
AS2Cwire
EN/SET
32 x 8 bit
ROM
Interface
GND
AutoBias Technology
Functional Description
Each of the four current source outputs is inde-
pendently 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.
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.
The AAT3141 requires only four external compo-
nents: 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
2
30mA each. The EN/SET AS Cwire serial interface
enables the AAT3141 and sets the current source
magnitudes.
10
3141.2007.03.1.3
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump
for White LED Applications
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 programma-
bility and real-time control of LED brightness.
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 loga-
rithmic 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.
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-cur-
rent applications.
Since the output current of the AAT3141 is pro-
grammable, no PWM (pulse width modulation) or
additional control circuitry are needed to control
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.
IOUT (typ)
(mA)
IOUT (typ)
(mA)
IOUT (typ)
(mA)
IOUT (typ)
(mA)
Code
Code
Code
Code
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
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
10
11
12
13
14
15
16
Table 2: Constant Current Source Output Nominal Programming Levels.
3141.2007.03.1.3
11
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump
for White LED Applications
2
T
LAT. Address or data is differentiated by the num-
AS Cwire Serial Interface
ber of EN/SET rising edges. Since the data regis-
ters are 5 bits each, the differentiating number of
The current source output magnitude is controlled
2
2
by the AS Cwire serial digital input. AS Cwire adds
addressing capability for multiple data registers
5
pulses is 2 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 ris-
ing edges, signifying a particular address, followed
by a pause with EN/SET held high for the TLAT time-
out 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 corre-
sponding 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.
2
over the Simple Serial Control™ (S Cwire™),
which is only capable of controlling a single regis-
ter. 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 out-
put D4.
Three addresses are used to control the two regis-
ters. Address 0 addresses both registers simulta-
neously 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 cur-
rent level settings. Address 2 addresses Register
2 for D4 current level settings.
2
2
As with S Cwire, AS Cwire relies on the number of
rising edges of the EN/SET pin to address and load
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.
2
the registers. AS Cwire latches data or address
after the EN/SET pin has been held high for time
Address
EN/SET Rising Edges
Data Register
0
1
2
33
34
35
1 & 2: D1-D4
1:
2:
D1-D3
D4
2
Table 2: AS Cwire Serial Interface Addressing.
2
AS Cwire Serial Interface Timing
Address
Data
THI
TLAT
TLO
TLAT
EN/SET
1
2
33
34
1
2 . . .
n <= 32
0
Address
Data Reg 1
Data Reg 2
1
0
0
n
12
3141.2007.03.1.3
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump
for White LED Applications
DC/DC boost converter white LED backlight solu-
tions. The AAT3141 soft-start feature prevents
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 for-
ward voltage specifications ranging from 1.0V to
4.3V. LED applications may include main and sub-
LCD display backlighting, camera photo-flash appli-
cations, color (RGB) LEDs, infrared (IR) diodes for
remotes, and other loads benefiting from a controlled
output current generated from a varying input volt-
age. 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.
noise transient effects associated with inrush cur-
rents during start-up of the charge pump circuit.
Power Efficiency and Device Evaluation
The charge pump efficiency discussion in the follow-
ing 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 dif-
ficult to measure efficiency in terms of a percent
value comparing input power over output power.
Since the AAT3141 outputs are pure constant cur-
rent 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 out-
put drive current will be maintained as a constant.
In some instances (e.g., in high luminous output
applications such as photo flash), it may be neces-
sary 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.
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 to the device for a given LED current drive
level. The best white LED driver for a given applica-
tion should be based on trade-offs of size, external
component count, reliability, operating range, and
total energy usage...not just % efficiency.
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 con-
stant current source will be set for a maximum volt-
age. 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 cur-
rent source outputs to ground.
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 differ-
ent efficiency values. Refer to the following two sec-
tions for explanations of each operational mode.
Device Switching Noise Performance
The AAT3141 operates at a fixed frequency of
approximately 1MHz to control noise and limit har-
monics that can interfere with the RF operation of
cellular telephone handsets or other communica-
tion 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
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 volt-
age across the load connected to the constant cur-
rent source outputs. When in load switch mode,
3141.2007.03.1.3
13
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump
for White LED Applications
the voltage conversion efficiency is defined as out-
put power divided by input power:
POUT
PIN
VOUT × IOUT
=
VOUT
η =
=
VIN × 1.5IOUT 1.5VIN
-or-
POUT
PIN
η =
VOUT
⎛
⎝
⎞
⎠
η(%) = 100
The expression to define the ideal efficiency (η)
can be rewritten as:
1.5V
IN
For a charge pump with an output of 5V and a nom-
inal 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 agree-
ment for output load conditions from 1mA to 100mA.
Efficiency will decrease as load current drops below
POUT VOUT × IOUT VOUT
η =
=
=
PIN
VIN × IOUT
VIN
-or-
0.05mA or when the level of VIN approaches VOUT
.
V
⎛
⎝
⎞
⎠
OUT
η(%) = 100
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.
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 (η) can be
simply defined as a linear voltage regulator with an
effective output voltage that is equal to one and
one half or two times the input voltage. Efficiency
(η) for an ideal 1.5X charge pump can typically be
expressed as the output power divided by the input
power:
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 per-
formance. 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 100mΩ. 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 lev-
els, then the capacitor size may be decreased.
POUT
PIN
η =
Capacitor Characteristics
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 (η) can be rewritten as:
Ceramic composition capacitors are highly recom-
mended over all other types of capacitors for use
with the AAT3141. Ceramic capacitors offer many
advantages over their tantalum and aluminum elec-
trolytic counterparts. A ceramic capacitor typically
has very low ESR, is lowest cost, has a smaller
PCB footprint, and is non-polarized. Low ESR
ceramic capacitors help maximize charge pump
transient response. Since ceramic capacitors are
non-polarized, they are not prone to incorrect con-
nection damage.
14
3141.2007.03.1.3
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump
for White LED 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.
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 compo-
sition, and ambient temperature. Capacitor ESR is
typically measured in milliohms for ceramic capac-
itors and can range to more than several ohms for
tantalum or aluminum electrolytic capacitors.
Thermal Protection
The AAT3141 has a thermal protection circuit that
will shut down the charge pump if the die tempera-
ture rises above the thermal limit, as is the case
during a short-circuit of the CP pin.
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 low-cost Y5V and Z5U
dielectrics, but capacitors greater than 1µF are usu-
ally not required for AAT3141 applications.
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 appli-
cations using single-cell lithium-ion/polymer batter-
ies and 3-series connected dry cells (3.6V).
3141.2007.03.1.3
15
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump
for White LED Applications
Ordering Information
1
2
Package
TSOPJW-12
Marking
LYXYY
Part Number (Tape and Reel)
AAT3141ITP-T1
All AnalogicTech products are offered in Pb-free packaging. The term “Pb-free” means
semiconductor products that are in compliance with current RoHS standards, including
the requirement that lead not exceed 0.1% by weight in homogeneous materials. For more
information, please visit our website at http://www.analogictech.com/pbfree.
Package Information
TSOPJW-12
+ 0.10
- 0.05
0.20
0.50 BSC 0.50 BSC 0.50 BSC 0.50 BSC 0.50 BSC
7° NOM
0.04 REF
3.00 0.10
4° 4°
5
0.45 0.1
0.055 0.045
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.
© Advanced Analogic Technologies, Inc.
AnalogicTech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AnalogicTech product. No circuit patent licenses, copyrights, mask work
rights, or other intellectual property rights are implied. AnalogicTech reserves the right to make changes to their products or specifications or to discontinue any product or service with-
out notice. Except as provided in AnalogicTech’s terms and conditions of sale, AnalogicTech assumes no liability whatsoever, and AnalogicTech disclaims any express or implied war-
ranty relating to the sale and/or use of AnalogicTech products including liability or warranties relating to fitness for a particular purpose, merchantability, or infringement of any patent,
copyright or other intellectual property right. In order to minimize risks associated with the customer’s applications, adequate design and operating safeguards must be provided by the
customer to minimize inherent or procedural hazards. Testing and other quality control techniques are utilized to the extent AnalogicTech deems necessary to support this warranty.
Specific testing of all parameters of each device is not necessarily performed. AnalogicTech and the AnalogicTech logo are trademarks of Advanced Analogic Technologies Incorporated.
All other brand and product names appearing in this document are registered trademarks or trademarks of their respective holders.
Advanced Analogic Technologies, Inc.
830 E. Arques Avenue, Sunnyvale, CA 94085
Phone (408) 737-4600
Fax (408) 737-4611
16
3141.2007.03.1.3
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