AAT AAT3153

AAT3153
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
Features
The AAT3153 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 AAT3153 is capable of driving six
LED channels 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 VIN and VOUT) makes this part ideally
suited for small, battery-powered applications.
•
•
•
•
•
•
•
•
•
•
•
•
AnalogicTech's S2Cwire™ (Simple Serial Control™)
serial digital input is used to enable, disable, and
set current for each LED with eight settings (20mA
down to 50µA) including main and sub-display
group control. The AAT3153 consumes extremely
low current internally (50µA typical) at light load for
optimized efficiency.
Each output of the AAT3153 is equipped with builtin protection for VOUT short-circuit and auto-disable
for load short-circuit conditions. Built-in soft-start
circuitry prevents excessive inrush current during
start-up. A low current shutdown feature disconnects the load from VIN and reduces quiescent current to less than 1µA.
ChargePump™
VIN Range: 2.7V to 5.5V
Fully Programmable Current with Single Wire
— Eight-Step Current: 20mA to 50µA
— Individual Main-Sub Group Control
— Low IQ (50µA) at Light Load
Tri-Mode 1X, 1.5X, and 2X Charge Pump for
Maximum Efficiency and VF Coverage
Drives Up to Six LED Channels
No Inductors, Low Noise Operation
1MHz Constant Switching Frequency
Small Application Circuit
Built-In Thermal Protection
Built-In Auto-Disable for Short-Circuit
Automatic Soft Start
IQ <1µA in Shutdown
Thermally-Enhanced 4x4mm 16-Pin QFN
Package
Applications
•
•
•
•
Color (RGB) Lighting
Programmable Current Sinks
White LED Backlighting
White Photo Flash for Digital Still Cameras
The AAT3153 is available in a Pb-free, space-saving,
thermally-enhanced 16-pin 4x4mm QFN package.
Typical Application
VIN
2.7V to 5.5V
C1+
C1
1µF
CIN
1µF
C1C2+
C2
1µF
AAT3153
C2VOUT
D1
D2
D3
D4
D5
D6
COUT
1µF
EN/SET
D1
EN/SET
D2
D3
D4
D5
GND
3153.2005.12.0.93
D6
1
Preliminary Information
General Description
AAT3153
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
Pin Descriptions
Pin #
Symbol
Function
1
2
3
4
D6
EN/SET
N/C
VOUT
5
6
7
8
9, 11
10
12
13
14
15
16
EP
C2+
C1+
C1C2GND
IN
D1
D2
D3
D4
D5
Current sink input #6.
S2Cwire serial interface control pin.
No connection.
Charge pump output to drive load circuit. Requires 1µF capacitor connected between this
pin and ground.
Flying capacitor 2 positive terminal. Connect a 1µF capacitor between C2+ and C2-.
Flying capacitor 1 positive terminal. Connect a 1µF capacitor between C1+ and C1-.
Flying capacitor 1 negative terminal.
Flying capacitor 2 negative terminal.
Ground.
Input power supply. Requires 1µF capacitor connected between this pin and ground.
Current sink input #1.
Current sink input #2.
Current sink input #3.
Current sink input #4.
Current sink input #5.
Exposed paddle (bottom); connect to GND directly beneath package.
Pin Configuration
QFN44-16
(Top View)
15
13
16
14
D4
1
12
D1
EN/SET
2
11
GND
N/C
3
10
IN
VOUT
4
9
GND
AAT3153
8
7
6
5
C2C1-
C1+
C2+
2
D2
D3
D5
D6
3153.2005.12.0.93
AAT3153
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
Absolute Maximum Ratings1
Symbol
VIN
VEN/SET
IOUT2
TJ
TLEAD
Description
Input Voltage
EN/SET to GND Voltage
Maximum DC Output Current
Operating Junction Temperature Range
Maximum Soldering Temperature (at leads, 10 sec)
Value
Units
-0.3 to 6
-0.3 to VIN + 0.3
180
-40 to 150
300
V
V
mA
°C
°C
Value
Units
2.0
50
W
°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.
3153.2005.12.0.93
3
AAT3153
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
2.0
3.7
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
EN/SET = 0
ISET = 30mA, TA = 25°C
Shutdown Current
ISINK Average Current Accuracy
Current Matching Between Any
I(D-Match)
VF:D1:D4 = 3.6V
Two Current Sink Inputs2, 3
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
50
18
20
1
22
µA
µA
mA
0.5
%
150
mV
100
1000
µs
kHz
0.4
1.4
0.3
75
50
-1
mA
75
500
500
1
V
V
µs
ns
µs
µs
µs
µA
1. The AAT3153 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.
3. Specification applies only to the tri-mode charge pump.
4
3153.2005.12.0.93
AAT3153
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
Typical Characteristics
Efficiency vs. Supply Voltage
Turn-On to 1X Mode
(VIN = 4.2V; 20mA Load)
100
10mA
VF = 3.1V
20mA
VF = 3.4V
EN
(2V/div)
Efficiency (%)
90
80
CP
(2V/div)
VSINK
(500mV/div)
70
60
IIN
(200mA/div)
50
2.8
3.0
3.2
3.4
3.6
3.8
4.0
4.2
Supply Voltage (V)
Time (100µs/div)
Turn-On to 1.5X Mode
Turn-On to 2X Mode
(VIN = 3.8V; 20mA Load)
(VIN = 2.8V; 20mA Load)
EN
(2V/div)
EN
(2V/div)
CP
(2V/div)
VSINK
(500mV/div)
CP
(2V/div)
VSINK
(500mV/div)
IIN
(200mA/div)
IIN
(200mA/div)
Time (100µs/div)
Time (100µs/div)
Turn-Off from 1.5X Mode
Current Matching vs. Temperature
(VIN = 3.5V; 20mA Load)
20.2
Channel 1
Channel 2
EN
(2V/div)
Current (mA)
20.0
VF
(1V/div)
IIN
(100mA/div)
19.8
Channel 5
19.6
Channel 3
19.4
Channel 4
Channel 6
19.2
-40
Time (100µs/div)
3153.2005.12.0.93
-20
0
20
40
60
80
Temperature (°°C)
5
AAT3153
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
Typical Characteristics
Load Characteristics
Load Characteristics
(VIN = 4.0V; 1.5X Mode; 20mA Load)
(VIN = 3.1V; 2X Mode; 20mA Load)
VIN
(40mV/div)
VIN
(40mV/div)
CP
(40mV/div)
CP
(40mV/div)
VSINK
(40mV/div)
VSINK
(40mV/div)
Time (500ns/div)
Time (500ns/div)
TLAT vs. VIN
TOFF vs. VIN
350
400
350
300
-40°C
300
TOFF (µ
µs)
TLAT (µ
µs)
250
200
150
25°C
85°C
100
-40°C
250
200
25°C
150
85°C
100
50
50
0
0
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
VIN (V)
VIN (V)
Input Ripple vs. VIN
Amplitude (mV)
25
30mA
20
15
10
20mA
10mA
5
0
2.50
2.67
2.84
3.01
3.18
3.35
3.52
3.69
3.86
4.03
4.20
VIN (V)
6
3153.2005.12.0.93
AAT3153
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
Typical Characteristics
VIH vs. VIN
VIL vs. VIN
1.2
1.2
1.1
1.1
-40°C
1
0.9
0.9
0.8
0.8
0.7
25°C
0.6
85°C
VIL (V)
VIH (V)
1
0.7
0.6
0.5
0.5
0.4
0.4
0.3
0.3
0.2
-40°C
25°C
85°C
0.2
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
VIN (V)
VIN (V)
3153.2005.12.0.93
7
AAT3153
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
Functional Block Diagram
C1+
C1- C2+
C2-
1X, 1.5X, and 2X
Charge Pump
VIN
VOUT
Soft-Start
Control
1MHz
Oscillator
Voltage
Reference
6 x 16 bit
ROM
EN/SET
S2Cwire
Interface
6 x 16 bit
ROM
D/A
D1
D/A
D2
D/A
D3
D/A
D4
D/A
D5
D/A
D6
D6
Functional Description
The AAT3153 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 AAT3153
8
charge pump is enabled when any of the four current sink inputs near 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 AAT3153
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).
3153.2005.12.0.93
AAT3153
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
The six constant current sink inputs (D1 to D6) can
drive six individual LEDs with a maximum current
of 20mA each. The unused sink inputs must be
connected to VOUT, otherwise the part will operate
only in 2X charge pump mode. The S2Cwire serial
interface enables the AAT3153 and sets the current
sink magnitudes. S2Cwire addressing allows independent control of two groups of current sink input:
D1-D4 and D5-D6.
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.
Constant Current Output Level Settings
When EN/SET is held low for an amount of time
greater than TOFF, the AAT3153 enters into shutdown
mode and draws less than 1µA from VIN. The internal data register is reset to zero during shutdown.
The constant current sink levels for D1 to D6 are
set via the serial interface. 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 (up to 1MHz data rate), the input
sink current of the AAT3153 can be changed successively to brighten or dim LEDs, giving the users
real-time control of LED brightness. Because the
inputs D1 to D6 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.
S2Cwire Serial Interface
The current sink input magnitude on the AAT3153 is
controlled by AnalogicTech's S2Cwire serial interface. The interface records rising edges of the
EN/SET pin and decodes them into 16 different
states, as indicated in Table 1. There are four brightness levels for the main or sub-display group with
the possibility of individually turning ON or OFF
each group. To further optimize power efficiency,
the AAT3153 also offers four low-current levels for
dim LED operation (Data 13 through 16). During
this low-current mode, the internal supply current
reduces to only 50µA typical.
3153.2005.12.0.93
Data
Main Group
(D1-D4)
IOUT (mA)
Sub Group
(D5-D6)
IOUT (mA)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
20
14
10
7
20
14
10
7
0
0
0
0
0.05
0.5
1
2
20
14
10
7
0
0
0
0
20
14
10
7
0.05
0.5
1
2
Table 1: AAT3153 Current Settings.
9
AAT3153
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
S2Cwire Serial Interface Timing
T HI
T LO
TOFF
TLAT
EN/SET
1
2
Data Reg
n
n <= 16
1
Auto-Disable Feature
The AAT3153 is equipped with an auto-disable feature for each LED channel. After the IC is enabled
and started up, a test current of 150µA (typical) is
forced through each sink channel. The channel will
be disabled if the voltage of that particular SINK pin
does not drop to certain threshold. This feature is
very convenient for disabling an unused channel or
during an LED fail short event.
Thermal Protection
The AAT3153 has a built-in 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 VOUT pin.
Applications Information
LED Selection
Although the AAT3153 is specifically intended for
driving white LEDs, the device can also 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 D6 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 applica-
10
n
0
tions such as photo flash), it may be necessary to
drive high-VF type LEDs. The low-dropout current
sinks in the AAT3153 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 AAT3153 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 AAT3153 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 the efficiency of the
charge pump section itself. Due to the unique circuit
architecture and design of the AAT3153, it is very difficult to measure efficiency in terms of a percent
value comparing input power over output power.
Since the AAT3153 inputs are pure constant current
sinks and typically drive individual loads, it is difficult
to measure the output voltage for a given input (D1
to D6) to derive an overall output power measurement. For any given application, white LED forward
voltage levels can differ, yet the load drive current
will be maintained as a constant.
3153.2005.12.0.93
AAT3153
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
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 AAT3153 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 inputs D1 through D6 for a
given constant current setting. Depending on the
combination of VIN and voltages sensed at the current sinks, the device will operate in load switch
mode. When any one of the voltages sensed at the
current sinks nears dropout, 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 for each
operational mode.
Load Switch Mode Efficiency
The AAT3153 load switch mode is operational at all
times and functions alone to enhance device power
conversion efficiency when VIN is greater than the
voltage across the load. When in load switch
mode, the voltage conversion efficiency is defined
as output power divided by input power:
P
η = OUT
PIN
The expression to define the ideal efficiency (η)
can be rewritten as:
η=
POUT VOUT × IOUT VOUT
=
=
PIN
VIN × IOUT
VIN
Charge Pump Section Efficiency
The AAT3153 contains a fractional charge pump that
will boost the input supply voltage when VIN is less
than the voltage required on the constant current
sink inputs. 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:
η=
POUT
VOUT × IOUT
VOUT
=
=
PIN
VIN × 1.5IOUT 1.5VIN
-or-
η(%) = 100
⎛ VOUT ⎞
⎝ 1.5VIN⎠
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.
-or-
Capacitor Characteristics
η(%) = 100
3153.2005.12.0.93
⎛ VOUT ⎞
⎝ VIN ⎠
Ceramic composition capacitors are highly recommended over all other types of capacitors for use
with the AAT3153. Ceramic capacitors offer many
advantages over their tantalum and aluminum elec-
11
AAT3153
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
trolytic counterparts. A ceramic capacitor 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.
12
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
AAT3153 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.
3153.2005.12.0.93
AAT3153
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
Ordering Information
Marking1
Package
Part Number (Tape and Reel)2
QFN44-16
AAT3153ISN-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
0.330 ± 0.050
Pin 1 Identification
13
16
0.650 BSC
1
R0.030Max
4
9
8
4.000 ± 0.050
2.400 ± 0.050
5
2.280 REF
Top View
0.0125 ± 0.0125
Bottom View
0.203 ± 0.025
0.900 ± 0.050
4.000 ± 0.050
Pin 1 Dot By Marking
0.450 ± 0.050
0.600 ± 0.050
QFN44-16
Side View
All dimensions in millimeters.
1. XYY = assembly and date code.
2. Sample stock is generally held on part numbers listed in BOLD.
3153.2005.12.0.93
13
AAT3153
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
© 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.
Advanced Analogic Technologies, Inc.
830 E. Arques Avenue, Sunnyvale, CA 94085
Phone (408) 737-4600
Fax (408) 737-4611
14
3153.2005.12.0.93