ANALOGICTECH AAT3141ITP-T1

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.
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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.
AnalogicTech's 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.
ChargePump™
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
Applications
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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
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
C1-
Flying capacitor 1 negative terminal.
4
C1+
Flying capacitor 1 positive terminal. Connect a 1µF capacitor between C1+
and C1-.
5
D3
Current source output #3.
6
D2
Current source output #2.
7
D4
Current source output #4.
8
D1
Current source output #1.
9
EN/SET
10
IN
11
GND
12
C2-
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
3141.2007.03.1.3
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump
for White LED Applications
Absolute Maximum Ratings1
Symbol
VIN
VEN/SET
IOUT2
TJ
Description
Input Voltage
EN/SET to GND Voltage
Maximum DC Output Current
Operating Junction Temperature Range
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
θJA
Description
4
Maximum Power Dissipation
Maximum Thermal Resistance
1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions other than the operating conditions specified is not implied. Only one Absolute Maximum Rating should be applied at any one time.
2. 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
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
I(D-Match)
ηCP
Output Current Accuracy2
Current Matching3
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
2.7
5.5
VD1:D4 = 2.0V, CP = 1X
550
No Load Current, CP = 1.5X
3
VIN = 3.5V, EN/SET = 0
VIN = 3.5V, TA = 25°C
-10
VIN = 3.5V, TA = 25°C, Code 28 17.1 19
VD1:D4 = 3.6V, VIN = 3.5V
-3 ±0.5
VIN = 3.5V, IOUT(TOTAL) = 120mA,
93
Measured from IN to CP
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
V
µA
mA
µA
%
mA
%
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
3141.2007.03.1.3
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump
for White LED Applications
Typical Characteristics
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
90
3.0VF
80
Efficiency (%)
Efficiency (%)
Unless otherwise noted, VIN = 3.5V, CIN = CCP = C1 = C2 = 1µF, TA = 25°C.
70
60
50
3.5VF
Code 26
80
70
60
50
Code 28
40
40
Code 32
30
30
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
Efficiency (%)
90
Code 26
80
70
60
50
40
Code 28
Code 32
30
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
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
Line Response
(1.5X Mode, 4x19mA Load)
(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
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)
μs/div)
Time (1μ
6
μs/div)
Time (1μ
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
Charge Pump to Load Switch
(1.5X Mode, 4x19mA Load)
(1.5X Mode, 4x30mA Load)
VIN
(500mV/div)
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)
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
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)
3141.2007.03.1.3
Time (2ms/div)
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
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
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
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
VDIODE = 3.0V
10
3.1
3.5
100
50
0
2.7
150
3.9
4.3
4.7
5.1
5.5
VDIODE = 3.0V
0
2.7
3.1
3.5
3.9
4.3
4.7
Input Voltage (V)
Input Voltage (V)
Diode Current vs. Input Voltage
VIH and VIL vs. VIN
5.1
5.5
(30mA, 15mA Settings)
0.850
40
0.825
IDIODE (mA)
35
0.800
VDIODE = 3.4V
0.775
30
VIH
0.750
0.725
25
VIL
0.700
20
0.675
VDIODE = 3.4V
0.650
15
0.625
0.600
10
2.7
3.1
3.5
3.9
4.3
Input Voltage (V)
3141.2007.03.1.3
4.7
5.1
5.5
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Input Voltage (V)
9
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
C1C2+
C2-
CP
32 x 8 bit
ROM
EN/SET
AS2Cwire
Interface
32 x 8 bit
ROM
D/A
D1
D/A
D2
D/A
D3
D/A
D4
GND
Functional Description
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.
10
AutoBias Technology
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.
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.
3141.2007.03.1.3
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.
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 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
AS2Cwire Serial Interface
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.
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.
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
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.
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.
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.
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
3141.2007.03.1.3
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump
for White LED Applications
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 subLCD 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.
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-topeak, typically ten times less than inductor-based
3141.2007.03.1.3
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.
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 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,
13
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump
for White LED Applications
the voltage conversion efficiency is defined as output power divided by input power:
POUT
PIN
η=
The expression to define the ideal efficiency (η)
can be rewritten as:
P
V
×I
V
η = OUT = OUT OUT = OUT
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 (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:
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 (η) can be rewritten as:
14
η=
VOUT × IOUT
VOUT
POUT
=
=
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 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 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 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 connection damage.
3141.2007.03.1.3
AAT3141
High Efficiency 1X/1.5X/2X Charge Pump
for White LED Applications
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 low-cost Y5V and Z5U
dielectrics, but capacitors greater than 1µF are usually not required for AAT3141 applications.
3141.2007.03.1.3
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 short-circuit 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 lithium-ion/polymer batteries and 3-series connected dry cells (3.6V).
15
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
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
2.85 ± 0.20
2.40 ± 0.10
0.10
0.20 +- 0.05
0.50 BSC 0.50 BSC 0.50 BSC 0.50 BSC 0.50 BSC
7° NOM
0.04 REF
0.055 ± 0.045
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.
© 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 without notice. Except as provided in AnalogicTech’s terms and conditions of sale, AnalogicTech assumes no liability whatsoever, and AnalogicTech disclaims any express or implied warranty 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,
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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