ANALOGICTECH AAT3155

AAT3155
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
General Description
Features
The AAT3155 is a low noise, constant frequency
charge pump DC/DC converter that uses a trimode load switch (1X), fractional (1.5X), and doubling (2X) conversion to maximize efficiency for
white LED applications. The AAT3155 is capable of
driving up to four channels of LEDs at 20mA per
channel from a 2.7V to 5.5V input. The current
sinks 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 IN and OUTCP) make this part ideally suited for small, battery-powered applications.
•
•
VIN Range: 2.7V to 5.5V
Fully Programmable Current with Single Wire
— 16 Current Levels
— Four Low Current Settings Down to 50µA
Low IQ (50µA) for Low Current Mode
Tri-Mode 1X, 1.5X, and 2X Charge Pump for
Maximum Efficiency and VF Coverage
Drives up to Four Channels of LEDs
No Inductors, Low Noise Operation
1MHz Constant Switching Frequency
Small Application Circuit
Built-In Thermal Protection
Automatic Soft Start
IQ <1µA in Shutdown
2.85x3.0mm TSOPJW-12 Package
•
•
•
•
•
•
•
•
•
•
AnalogicTech's S2Cwire™ (Simple Serial Control™)
serial digital input is used to enable, disable, and set
current for each LED with 16 settings down to 50μA.
The low-current mode supply current can be as low
as 50μA to save power.
Each output of the AAT3155 is equipped with builtin protection for output short-circuit and auto-disable for load short-circuit conditions. Built-in softstart circuitry prevents excessive inrush current
during start-up. A low-current shutdown feature disconnects the load from the input and reduces quiescent current to less than 1μA.
ChargePump™
Applications
•
•
•
•
Color (RGB) Lighting
Programmable Current Sinks
White LED Backlighting
White Photo Flash for Digital Still Cameras
The AAT3155 is available in a Pb-free, space-saving 2.85x3.0mm 12-pin TSOPJW package.
Typical Application
C1+
C2+
C2
1µF
C1
1µF
C2-
C12.7V to 5.5V
IN
CIN
1µF
OUTCP
D1
AAT3155
GND
D2
D3
D4
COUT
1µF
D1
D2
EN/SET
EN/SET
D3
D4
3155.2006.05.1.1
1
AAT3155
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
Pin Descriptions
Pin #
Symbol
Function
1
D3
Current sink input #3.
2
D2
Current sink input #2.
3
D1
Current sink input #1.
4
GND
5
IN
6
C2-
Flying capacitor 2 negative terminal.
7
C2+
Flying capacitor 2 positive terminal. Connect a 1µF capacitor between C2+ and
C2-.
8
OUTCP
9
C1-
Flying capacitor 1 negative terminal.
10
C1+
Flying capacitor 1 positive terminal. Connect a 1µF capacitor between C1+ and
C1-.
11
EN/SET
12
D4
Ground.
Input power supply. Requires 1µF capacitor connected between this pin and
ground.
Charge pump output to drive load circuit. Requires 1µF capacitor connected
between this pin and ground.
S2Cwire serial interface control pin.
Current sink input #4.
Pin Configuration
TSOPJW-12
(Top View)
D3
D2
D1
GND
IN
C2-
2
1
12
2
11
3
10
4
9
5
8
6
7
D4
EN/SET
C1+
C1OUTCP
C2+
3155.2006.05.1.1
AAT3155
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
Absolute Maximum Ratings1
Symbol
VIN
VEN/SET
IOUT2
TJ
TLEAD
Description
Value
Units
-0.3 to 6
-0.3 to VIN + 0.3
150
-40 to 150
300
V
V
mA
°C
°C
Description
Value
Units
Maximum Power Dissipation4
Maximum Thermal Resistance
0.625
160
W
°C/W
Input Voltage to GND
EN/SET Voltage to GND
Maximum DC Output Current
Operating Junction Temperature Range
Maximum Soldering Temperature (at leads, 10 sec)
Thermal Information3
Symbol
PD
θJA
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.
3155.2006.05.1.1
3
AAT3155
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
Electrical Characteristics1
CIN = COUT = C1 = C2 = 1.0µF; TA = -40°C to +85°C, unless otherwise noted.
Typical values are TA = 25°C, VIN = 3.6V.
Symbol
Description
Conditions
Input Power Supply
VIN
Operation Range
ICC
ISHDN
IDX
Operating Current
Min
Typ
Max
Units
5.5
1
V
0.3
1
3
2.7
1X Mode, 3.0 ≤ VIN ≤ 5.5, Active,
No Load Current
1.5X Mode, 3.0 ≤ VIN ≤ 5.5, Active,
No Load Current
2X Mode, 3.0 ≤ VIN ≤ 5.5, Active,
No Load Current
50µA Setting, 1X Mode
VEN/SET = 0V
ISET = 20mA, TA = 25°C
VF:D1:D4=3.6V
Shutdown Current
ISINK Average Current Accuracy
I(D-Match)
Current Matching2
1X to 1.5X or 1.5X to 2X Transition
VTH
Threshold at Any ISINK Pin
Charge Pump Section
TSS
Soft-Start Time
FCLK
Clock Frequency
EN/SET
VEN(L)
Enable Threshold Low
VIN = 2.7V
VEN(H)
Enable Threshold High
VIN = 5.5V
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
mA
1
50
18
20
0.5
1
22
1
150
mV
100
1000
µs
kHz
0.4
1.4
0.3
75
50
-1
µA
µA
mA
%
75
500
500
1
V
V
µs
ns
µs
µs
µs
µA
1. The AAT3155 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. Current matching is defined as the deviation of any sink current from the average of all active channels.
4
3155.2006.05.1.1
AAT3155
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
Typical Characteristics
CIN = COUT = C1 = C2 = 1.0µF; TA = 25°C, VIN = 3.6V, unless otherwise noted.
Turn-On to 1X Mode
Efficiency vs. Supply Voltage
(VIN = 4.2V; 20mA Load)
100
Efficiency (%)
20mA/ch
VF = 3.4V
5mA/ch
VF = 3V
90
EN
(2V/div)
80
70
VOUT
(2V/div)
VSINK
(1V/div)
60
50
500µA/ch
VF = 2.7V
40
IIN
(100mA/div)
30
2.7
2.9
3.1
3.3
3.5
3.7
3.9
4.1
4.3
4.5
μs/div)
Time (200μ
Supply Voltage (V)
Turn-On to 1.5X Mode
Turn-On to 2X Mode
(VIN = 3.5V; 20mA Load)
(VIN = 2.8V; 20mA Load)
EN
(2V/div)
EN
(2V/div)
VOUT
(2V/div)
VOUT
(2V/div)
VSINK
(1V/div)
VSINK
(500mV/div)
IIN
(200mA/div)
IIN
(200mA/div)
μs/div)
Time (200μ
μs/div)
Time (200μ
Turn-Off from 1.5X Mode
Diode Current vs. Temperature
(VIN = 3.5V; 20mA Load)
(20mA/channel)
Diode Current (mA)
22.0
EN
(2V/div)
VF
(1V/div)
IIN
(100mA/div)
21.5
21.0
ID1
20.5
ID2
20.0
19.5
19.0
ID4
ID3
18.5
18.0
-40
μs/div)
Time (200μ
3155.2006.05.1.1
-25
-10
5
20
35
50
65
80
95
Temperature (°°C)
5
AAT3155
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
Typical Characteristics
CIN = COUT = C1 = C2 = 1.0µF; TA = 25°C, VIN = 3.6V, unless otherwise noted.
Load Characteristics
Load Characteristics
(VIN = 3.9V; 1.5X Mode; 20mA Load)
(VIN = 3.9V; 1.5X Mode; 14mA Load)
VIN
(40mV/div)
VIN
(40mV/div)
VCP
(40mV/div)
VCP
(20mV/div)
VSINK
(20mV/div)
VSINK
(20mV/div)
Time (500ns/div)
Time (500ns/div)
Load Characteristics
Load Characteristics
(VIN = 2.9V; 2X Mode; 20mA Load)
(VIN = 2.9V; 2X Mode; 14mA Load)
VIN
(40mV/div)
VIN
(40mV/div)
VCP
(40mV/div)
VCP
(40mV/div)
VSINK
(40mV/div)
VSINK
(40mV/div)
Time (500ns/div)
Time (500ns/div)
Input Ripple vs. Input Voltage
EN/SET Latch Timeout vs. Input Voltage
Input Ripple (mV)
12.0
EN/SET Latch Timeout (μ
μs)
14.0
20mA/channel
10.0
14mA/channel
8.0
6.0
4.0
10mA/
channel
2.0
0.0
2.5
3.0
3.5
4.0
4.5
Input Voltage (V)
6
5.0
5.5
350
300
250
-40°C
200
150
85°C
25°C
100
50
0
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
3155.2006.05.1.1
AAT3155
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
Typical Characteristics
CIN = COUT = C1 = C2 = 1.0µF; TA = 25°C, VIN = 3.6V, unless otherwise noted.
EN/SET Off Timeout vs. Input Voltage
Enable Threshold High vs. Input Voltage
Enable Threshold High (V)
EN/SET Off Timeout (μ
μs)
350
300
250
-40°C
200
150
100
25°C
85°C
50
0
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
1.4
1.2
-40°C
1.0
0.8
25°C
85°C
0.6
0.4
2.7
3.1
3.5
3.9
4.3
4.7
5.1
5.5
Input Voltage (V)
Enable Threshold Low (V)
Enable Threshold Low vs. Input Voltage
1.4
1.2
1.0
-40°C
0.8
0.6
0.4
2.7
25°C
3.1
3.5
3.9
85°C
4.3
4.7
5.1
5.5
Input Voltage (V)
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AAT3155
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
Functional Block Diagram
C1+
C1- C2+
C2-
1X, 1.5X, 2X
Charge Pump
IN
OUTCP
Soft-Start
Control
1MHz
Oscillator
Voltage
Reference
6 x 16 bit
ROM
EN/SET
S2Cwire
Interface
D/A
D1
D/A
D2
D/A
D3
D/A
D4
GND
Functional Description
The AAT3155 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 sink input and sets the load
switch and charge pump modes based on the input
battery voltage and the current sink input voltage.
As the battery discharges over time, the AAT3155
charge pump is enabled when any of the four current sink inputs nears dropout. The charge pump
initially starts in 1.5X mode. If the charge pump
output droops enough for any current source output to become close to dropout, the charge pump
will automatically transition to 2X mode. The
AAT3155 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 (COUT).
8
The four constant current sink inputs (D1 to D4)
can drive four individual LEDs with a maximum current of 20mA each. The unused sink inputs must be
connected to OUTCP, otherwise the part will operate only in 2X charge pump mode. The S2Cwire
serial interface enables the AAT3155 and sets the
current sink magnitudes.
Constant Current Output Level Settings
The constant current sink levels for D1 to D4 are set
via the serial interface according to a logarithmic
scale for the first 12 codes and a separate low-current scale for the last four codes. For the first 12
codes, each code is approximately 1.5dB lower than
the previous code. In this manner, LED brightness
appears linear with each increasing code count.
Because the inputs D1 to D4 are true independent
constant current sinks, the voltage observed on any
single given input will be determined by the actual
forward voltage (VF) for the LED being driven.
Since the input current sinks of the AAT3155 are
programmable, no PWM (pulse width modulation) or
3155.2006.05.1.1
AAT3155
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
The S2Cwire serial interface has flexible timing.
Data can be clocked-in at speeds greater than
1MHz, or much slower, such as 15kHz. After data
is submitted, EN/SET is held high to latch the data.
Once EN/SET has been held in the logic high state
for time TLAT, the programmed current becomes
active and the internal data register is reset to zero.
For subsequent current level programming, the
number of rising edges corresponding to the
desired code must be entered on the EN/SET pin.
additional control circuitry is 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 input sink current of the AAT3155 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.
When EN/SET is held low for an amount of time
greater than TOFF, the AAT3155 enters into shutdown
mode and draws less than 1µA from VIN. The internal
data register is reset to zero during shutdown.
S2Cwire Serial Interface
The current level magnitude is controlled by
AnalogicTech's Simple Serial Control (S2Cwire)
serial interface. The interface records rising edges
of the EN/SET pin and decodes them into 16 different states. The 16 current level settings available
are indicated in Table 1.
Data
Output
(mA/Ch)
Data
Output
(mA/Ch)
1
2
3
4
5
6
7
8
20.0
17.0
14.0
12.0
10.0
8.6
7.0
6.0
9
10
11
12
13
14
15
16
5.0
4.2
3.4
2.8
1.0
0.5
0.1
0.05
Auto-Disable Feature
The AAT3155 is equipped with an auto-disable feature for each LED channel. After the IC is enabled
and started up, a test current of 100µA (typical) is
forced through each sink channel. The channel will
be disabled if the voltage of that particular SINK pin
does not drop to a certain threshold. This feature is
very convenient for disabling an unused channel or
during an LED fail-short event.
Thermal Protection
The AAT3155 has a thermal protection circuit that
will shut down the charge pump if the die temperature rises above the thermal limit, as would be the
case during a short circuit of the OUTCP pin.
Table 1: Current Level Settings.
S2Cwire Serial Interface Timing
T HI
T LO
TOFF
TLAT
EN/SET
1
Data Reg
3155.2006.05.1.1
2
n
1
n <= 16
n
0
9
AAT3155
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
Applications Information
Although the AAT3155 is designed for driving white
LEDs, the device also can be used to drive most
types of LEDs with forward voltage specifications
ranging from 2.0V to 4.7V. 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 input current sinks 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-sinks in the AAT3155
make it capable of driving LEDs with forward voltages as high as 4.7V at full current from an input
supply as low as 3.0V. Outputs can be paralleled to
drive high-current LEDs without complication.
Device Switching Noise Performance
The AAT3155 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
DC/DC boost converter white LED backlight solutions. The AAT3155 soft-start feature prevents
noise transient effects associated with inrush currents during start-up of the charge pump circuit.
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
10
when choosing capacitors. If the LED current
sources are programmed only 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 AAT3155. 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 to 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 generally have tight tolerance and are
very stable over temperature. Larger capacitor values are usually composed of X7R, X5R, Z5U, or
Y5V dielectric materials. Large ceramic capacitors
(i.e., greater than 2.2µF) are often available in lowcost Y5V and Z5U dielectrics, but capacitors
greater than 1µF are not typically required for
AAT3155 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.
3155.2006.05.1.1
AAT3155
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
Ordering Information
Package
Marking1
Part Number (Tape and Reel)2
TSOPJW-12
QOXYY
AAT3155ITP-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
+ 0.10
- 0.05
2.40 ± 0.10
0.20
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 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.
Customers are advised to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. AnalogicTech
warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with AnalogicTech’s standard warranty. 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
3155.2006.05.1.1
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