Analogic AAT3123 High efficiency 1x/1.5x fractional charge pump for white led application Datasheet

AAT3123/23A/24
High Efficiency 1X/1.5X Fractional Charge
Pump for White LED Applications
General Description
Features
The AAT3123/23A/24 is a low noise, constant frequency charge pump DC/DC converter that uses a
dual mode load switch (1X) and fractional (1.5X)
conversion to maximize efficiency for white LED
applications. The device can be used to produce
current levels up to 20mA to drive up to six LEDs
from a 2.7V to 5.5V input. Outputs may be operated individually or paralleled for driving higher-current LEDs. A low external parts count (two 1µF flying capacitors and two small 1µF capacitors at VIN
and OUT) make the AAT3123/23A/24 ideally suited
for small battery-powered applications.
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•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
AnalogicTech’s Simple Serial Control™ (S2Cwire™)
interface is used to enable, disable, and set the
LED drive current with a 32-level logarithmic scale
LED brightness control. The AAT3123/23A/24 has a
thermal management system to protect the device
in the event of a short-circuit condition at the 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. A low-current shutdown feature
disconnects the load from VIN and reduces quiescent current to less than 1µA. The device also integrates a test current/auto-disable feature for each
channel. The AAT3123/23A is available in a very
small, Pb-free 12-pin TSOPJW package. The six
output AAT3124 is available in a Pb-free 16-pin
4x4mm QFN package.
ChargePump™
VIN Range: 2.7V to 5.5V
Dual Mode 1X and 1.5X Charge Pump for
Maximum Efficiency
Drives Low-VF and High-VF Type LEDs
Up to Six 20mA Outputs (AAT3124)
Up to Four 20mA Outputs (AAT3123/23A)
32-Position Logarithmic Scale with Digital
Control
Simple Serial Control (S2Cwire) Interface
Low Noise Constant Frequency Operation
1MHz Switching Frequency
Small Application Circuit
Regulated Output Current
Automatic Soft Start
No Inductors
IQ <1µA in Shutdown
Temperature Range: -40°C to +85°C
12-Pin TSOPJW Package (AAT3123/23A)
16-Pin 4x4mm QFN Package (AAT3124)
Applications
•
•
•
•
Color (RGB) Lighting
Programmable Current Source
White LED Backlighting
White Photo Flash for DSCs
Typical Application
VIN
C1+
C1
1µF
VBATTERY
C1C2+
VOUT
CIN
1µF
C OUT
1µF
AAT3124
C2
1µF
C2-
EN/SET
EN/SET
D1
D2
D3
D4
D5
D6
GND
D6
3123.2005.12.1.4
D5
D4
D3
D2
D1
1
AAT3123/23A/24
High Efficiency 1X/1.5X Fractional Charge
Pump for White LED Applications
Pin Descriptions
Pin #
AAT3123/23A
(TSOPJW-12)
AAT3124
(QFN44-16)
Symbol
1
10
C2+
2
9
OUT
3
4
7
6
C1C1+
5
6
7
8
9
10
5
4
1
16
15
14
D4
D3
D2
D1
EN/SET
IN
11
12
12
11
2
3
8, 13
EP
GND
C2D5
D6
N/C
Function
Flying capacitor 2 positive terminal. Connect a 1µF capacitor
between C2+ and C2-.
Charge pump output. Requires 1µF capacitor connected
between this pin and ground.
Flying capacitor 1 negative terminal.
Flying capacitor 1 positive terminal. Connect a 1µF capacitor
between C1+ and C1-.
Current source output #4.
Current source output #3.
Current source output #2.
Current source output #1.
Control pin using S2Cwire serial interface.
Input power supply. Requires 1µF capacitor connected between
this pin and ground.
Ground.
Flying capacitor 2 negative terminal.
Current source output #5.
Current source output #6.
No connection.
Exposed paddle (bottom); connect to GND directly beneath
package.
Pin Configuration
TSOPJW-12
(Top View)
9
8
7
12
GND
11
C2-
3
10
C2+
4
9
OUT
D2
1
D5
2
D6
D3
AAT3124
8
7
6
5
N/C
C1-
C1+
D4
2
13
6
10
14
4
5
AAT3123
AAT3123A
N/C
IN
3
C2GND
IN
EN/SET
D1
D2
15
11
16
12
2
D1
1
EN/SET
C2+
OUT
C1C1+
D4
D3
QFN44-16
(Top View)
3123.2005.12.1.4
AAT3123/23A/24
High Efficiency 1X/1.5X Fractional Charge
Pump for White LED Applications
Absolute Maximum Ratings1
Symbol
VIN
VOUT
FB, VEN/SET
VEN/SET(MAX)
IOUT2
TJ
Description
Input Voltage
Charge Pump Output
FB or EN/SET to GND Voltage
Maximum EN/SET to Input Voltage
Maximum DC Output Current
Operating Junction Temperature Range
Value
Units
-0.3 to 6
-0.3 to 6
-0.3 to 6
0.3
150
-40 to 150
V
V
V
V
mA
°C
Value
Units
Thermal Information3
Symbol
Description
θJA
Thermal Resistance
PD
Maximum Power Dissipation
QFN44-16
TSOPJW-12
QFN44-164
TSOPJW-125
50
160
2.0
0.625
°C/W
W
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 20mW/°C above 25°C.
5. Derate 6.25mW/°C above 25°C.
3123.2005.12.1.4
3
AAT3123/23A/24
High Efficiency 1X/1.5X Fractional 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 = 3.5V.
Symbol
Description
Input Power Supply
VIN
Operation Range
Icc
Operating Current
ISHDN(MAX)
IDX
I(D-Match)
ηCP
Charge Pump
TSS
FCLK
EN/SET
VEN(L)
VEN(H)
TEN/SET LO
TEN/SET HI
TOFF
Input Current
Shutdown Current
Output Current
Current Matching Between Any
Two Outputs
Charge Pump Section Efficiency
Conditions
Min
Max
Units
1.8
5.5
3.5
V
mA
1
22
µA
mA
2.7
3.0 ≤ VIN ≤ 5.5, Active,
No Load Current
EN = 0
VIN = 3.5V, Code = 32, TA = 25°C
VD1:D4 = 3.6V, VIN = 3.5V
VD5:VD6 = 3.6V, VIN = 3.5V
VIN = 3.5V, IOUT(TOTAL) = 120mA,
Measured from IN to OUT
18
Section
Soft-Start Time
Clock Frequency
Enable Threshold Low
Enable Threshold High
EN/SET Low Time
Minumum EN/SET High Time
EN/SET Off Timeout
EN/SET Input Leakage
Typ
20
0.5
0.5
93
%
%
200
1000
VIN = 2.7V to 5.5V
VIN = 2.7V to 5.5V
µs
kHz
0.5
1.4
0.3
75
50
-1
500
1
V
V
µs
ns
µs
µA
1. The AAT3123/4 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.
4
3123.2005.12.1.4
AAT3123/23A/24
High Efficiency 1X/1.5X Fractional Charge
Pump for White LED Applications
Typical Characteristics
Unless otherwise noted, VIN = 3.5V, CIN = COUT = C1 = C2 = 1µF, TA = 25°C.
Efficiency vs. Input Voltage
Efficiency vs. Input Voltage
(4x20mA)
(4x10mA)
100
100
95
VDIODE = 3.4V
VDIODE = 3.2V
90
85
VDIODE = 3.0V
80
75
70
65
VDIODE = 3.4V
VDIODE = 3.2V
90
Efficiency (%)
Efficiency (%)
95
85
VDIODE = 3.0V
80
75
70
65
60
60
55
55
50
50
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
2.7
2.9
3.1
3.3
3.5
Input Voltage (V)
3.7
3.9
4.1
4.3
4.5
4.7
4.9
5.1
4.7
4.9
5.1
Input Voltage (V)
IDIODE vs. Input Voltage
IDIODE vs. Input Voltage
(4x20mA)
(4x10mA)
85
45
VDIODE = 3.4V
VDIODE = 3.2V
75
IDIODE (mA)
IDIODE (mA)
80
VDIODE = 3.0V
70
VDIODE = 3.0V
65
60
2.7
35
2.9
3.1
3.3
3.5
3.7
3.9
4.1
4.3
4.5
4.7
4.9
5.1
2.7
2.9
3.1
3.3
3.5
Input Voltage (V)
2.6
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6 VDIODE = 3.0V
0.4
0.2
0.0
2.7 2.9 3.1 3.3
3.9
4.1
4.3
4.5
VIH and VIL vs. VIN
0.850
0.825
0.800
0.775
VIH
0.750
0.725
VDIODE = 3.4V
VIL
0.700
0.675
VDIODE = 3.2V
0.650
0.625
0.600
3.5
3.7
3.9
4.1
4.3
Input Voltage (V)
3123.2005.12.1.4
3.7
Input Voltage (V)
Quiescent Current vs. Input Voltage
Quiescent Current (mA)
VDIODE = 3.4V
VDIODE = 3.2V
40
4.5
4.7
4.9
5.1
2.5
3.0
3.5
4.0
4.5
5.0
5.5
Input Voltage (V)
5
AAT3123/23A/24
High Efficiency 1X/1.5X Fractional Charge
Pump for White LED Applications
Typical Characteristics
Unless otherwise noted, VIN = 3.5V, CIN = COUT = C1 = C2 = 1µF, TA = 25°C.
Turn-On to Full-Scale Charge Pump
Turn-On to Full-Scale Load Switch
EN/SET
(1V/div)
EN/SET
(1V/div)
OUT
(2V/div)
OUT
(2V/div)
VDIODE
(1V/div)
VDIODE
(2V/div)
IIN
(200mA/div)
IIN
(100mA/div)
Time (50µs/div)
Time (50µs/div)
Charge Pump to Load Switch
Load Switch to Charge Pump
(80mA)
(80mA)
VIN
(10mV/div)
VIN
(20mV/div)
OUT
(2V/div)
OUT
(1V/div)
VDIODE
(2V/div)
VDIODE
(1V/div)
IIN
(100mA/div)
IIN
(200mV/div)
Time (50µs/div)
Time (50µs/div)
Turn-Off
80mA Load Characteristics
VIN
20mV/div
EN/SET
(1V/div)
VDIODE
(2V/div)
OUT
IIN
(100mA/div)
VDIODE
Time (200µs/div)
6
Time (1µs/div)
3123.2005.12.1.4
AAT3123/23A/24
High Efficiency 1X/1.5X Fractional Charge
Pump for White LED Applications
Functional Block Diagram
VIN
Soft-Start
Control
C1+
1x/1.5x
Charge
Pump
1MHz
Oscillator
C1C2+
C2-
Voltage
Reference
OUT
D1
Current
Current
Reference
Quad
Output
DAC
D2
D3
D4
EN/SET
S2Cwire
Interface
Dual
Output
DAC
32 x 8 bit
ROM
D5*
D6*
*AAT3124 only
GND
Functional Description
The AAT3123/23A/24 is a dual mode load switch
(1X) and high efficiency (1.5X) fractional charge
pump device intended for white LED backlight
applications. The fractional charge pump consists
of a low dropout linear voltage regulator followed
by a 1.5X charge pump with multiple currentsource outputs. To maximize power conversion
efficiency, an internal feedback control sensing circuit monitors the voltage required on the constant
current source outputs. This control circuit then
sets the load switch and charge pump functions
based upon the input voltage level versus the output voltage level needed. This function significantly enhances overall device efficiency when the
input voltage level is greater than the voltage
required at the constant current source outputs.
For the AAT3123/23A, the 1X load switch/1.5X
charge pump mode is decided on the voltage
sensed on the output D1. The AAT3124 bases the
1X load switch/1.5X charge pump mode decision
on the voltage levels sensed on either the D1-D4
output group or the D5-D6 output group, whichever is greater. Switchover between the 1.5X
(charge-pump) operating mode and the 1X (load
switch) mode occurs automatically (as a function of
input and output voltages) and does not require
user intervention to maintain maximum efficiency.
3123.2005.12.1.4
The AAT3123/23A/24 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 output capacitor (COUT). The
LDO/1.5X charge pump output is converted into
four (D1 to D4) or six (D1 to D4 and D5 to D6) constant current outputs to drive four or six individual
LEDs with a maximum current of 20mA each. The
current source output magnitude is controlled by
the EN/SET serial data S2Cwire interface. The interface records rising edges of the EN/SET pin and
decodes them into 32 individual current level settings each 1dB apart (see Table 1, Current Level
Settings). Code 32 is full scale, and Code 1 is full
scale attenuated by 31dB. The modulo 32 interface
wraps states back to State 1 after the 32nd clock.
With each EN/SET pulse, the output current increases by 1dB. To decrease the output current by 1dB,
31 EN/SET clock pulses are required. The counter
can be clocked at speeds up to 1MHz, so intermediate states are not visible. The first rising edge of
EN/SET enables the IC and initially sets the output
LED current to -31dB, the lowest setting equal to
525µA. Once the final clock cycle is input for the
desired brightness level, the EN/SET pin is held high
to maintain the device output current at the programmed level. The device is disabled 500µs after
the EN/SET pin transitions to a logic low state.
7
AAT3123/23A/24
High Efficiency 1X/1.5X Fractional Charge
Pump for White LED Applications
Applications Information
Constant Current Output Level Settings
The constant current source output amplitude for
outputs D1 to D6 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
D6 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.
Normalized Output Current Settings
1.0
Normalized I OUT (D1 to D6)
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0.0
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
Since the output current of the AAT3123/23A/24 is
programmable through its single-wire serial interface, no PWM (pulse width modulation) or 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." Furthermore, with its high-speed
serial interface (1MHz data rate), the output current
of the AAT3123/23A/24 can 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.
Code
IOUT
(mA)
Code
IOUT
(mA)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
0.549
0.627
0.706
0.784
0.863
1.020
1.098
1.255
1.412
1.569
1.804
1.961
2.275
2.510
2.824
3.137
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
3.529
4.000
4.471
5.020
5.647
6.353
7.059
7.922
8.941
10.039
11.216
12.627
14.118
15.843
17.804
20.000
Table 1: Constant Current Source Output
Programming Levels (mA).
8
3123.2005.12.1.4
AAT3123/23A/24
High Efficiency 1X/1.5X Fractional Charge
Pump for White LED Applications
EN/SET Serial Interface
The current source output magnitude is controlled
by the EN/SET pin, using AnalogicTech’s Simple
Serial Control (S2Cwire) interface. The interface
records rising edges of the EN/SET pin, and
decodes them into 32 individual current level settings each 1dB apart. Code 32 is full scale, and
Code 1 is full scale attenuated by 31dB. The modulo 32 interface wraps states back to State 1 after the
32nd clock, so 1dB of attenuation is achieved by
clocking the EN/SET pin 31 times. The counter can
be clocked at speeds up to 1MHz, so intermediate
states are not visible. The first rising edge of
EN/SET enables the IC and initially sets the output
LED current to -31dB, the lowest setting equal to
525µA. Once the final clock cycle is input for the
desired brightness level, the EN/SET pin is held
high to maintain the device output current at the
programmed level. The device is disabled 500µs
after the EN/SET pin transitions to a logic low state.
The EN/SET timing is designed to accommodate a
wide range of data rates. After the first rising edge
of EN/SET, the charge pump is enabled and reaches full capacity after the soft-start time (TSS). During
the soft-start time, multiple clock pulses may be
entered on the EN/SET pin to set the final output
current level with a single burst of clocks.
Alternatively, the EN/SET clock pulses may be
entered one at a time to gradually increase LED
brightness over any desired time period. A constant
current is sourced as long as EN/SET remains in a
logic high state. The current source outputs are
switched off after EN/SET has remained in a low
state for at least the tOFF timeout period.
EN/SET Timing
tHI
tOFF
tLO
EN/SET
Code
OFF
1
LED Selection
The AAT3123/23A/24 is specifically intended for driving white LEDs. However, the device design will
allow the AAT3123/23A/24 to drive most types of
LEDs with forward voltage specifications ranging
from 2.0V to 4.3V. LED applications may include
main and sub-LCD display backlighting, camera
photo-flash applications, color (RGB) LEDs, infrared
(IR) diodes for remotes, and other loads benefiting
from a controlled output current generated from a
varying input voltage. Since the D1 to D6 output current sources are matched with negligible voltage
dependence, 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
3123.2005.12.1.4
2
3
OFF
current sources in the AAT3123/23A/24 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.
Device Switching Noise Performance
The AAT3123/23A/24 operates at a fixed frequency
of approximately 1MHz to control noise and limit
harmonics that can interfere with the RF operation
of cellular telephone handsets or other communication devices. Back-injected noise appearing on the
input pin of the charge pump is 20mV peak-to-peak,
typically ten times less than inductor-based DC/DC
boost converter white LED backlight solutions. The
AAT3123/23A/24 soft-start feature prevents noise
transient effects associated with inrush currents
during start-up of the charge pump circuit.
9
AAT3123/23A/24
High Efficiency 1X/1.5X Fractional Charge
Pump for White LED Applications
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 AAT3123/23A/24, it is
very difficult to measure efficiency in terms of a percent value comparing input power over output power.
Since the AAT3123/23A/24 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 D6) 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 AAT3123/23A/24 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 or D6 for a given constant current setting.
Depending upon the case of VIN being greater than
the specific voltage seen across the load on D1 (or
D5 when the AAT3124 is used) 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 charge pump mode.
Each of these two modes will yield different efficiency values. Refer to the following two sections for
explanations of each operational mode.
η=
The expression to define the ideal efficiency (η)
can be rewritten as:
η=
10
POUT VOUT × IOUT
V
=
= OUT
VIN × IOUT
VIN
PIN
-or-
η(%) = 100
⎛ VOUT ⎞
⎝ VIN ⎠
Charge Pump Section Efficiency
The AAT3123/23A/24 contains a fractional charge
pump which will boost the input supply voltage in
the event where 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 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=
Load Switch Mode Efficiency
The AAT3123/23A/24 load switch mode is operational at all times and functions alone to enhance
device power conversion efficiency when the condition exists where VIN is greater than voltage
across the load connected to the constant current
source outputs. When in load switch mode, the
voltage conversion efficiency is defined as output
power divided by input power:
POUT
PIN
POUT
VOUT × IOUT
VOUT
=
=
PIN
VIN × 1.5IOUT 1.5VIN
-or-
η(%) = 100
⎛ VOUT ⎞
⎝ 1.5VIN⎠
3123.2005.12.1.4
AAT3123/23A/24
High Efficiency 1X/1.5X Fractional Charge
Pump for White LED Applications
For a charge pump with an output of 5 volts and a
nominal input of 3.5 volts, 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 AAT3123/23A/24. 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.
3123.2005.12.1.4
Ceramic Capacitor Materials
Ceramic capacitors less than 0.1µF are typically
made from NPO or C0G materials. NPO and C0G
materials typically have tight tolerance and are stable over temperature. Large capacitor values are
typically composed of X7R, X5R, Z5U, or Y5V
dielectric materials. Large ceramic capacitors, typically greater than 2.2µF, are often available in lowcost Y5V and Z5U dielectrics, but capacitors
greater than 1µF are typically not required for
AAT3123/23A/24 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.
Test Current/Channel Disable
Each channel of the output is equipped with test
current function. A small amount of current (~2µA)
is injected into each output current source to detect
the presence of load (LED). Unused channels that
are tied to ground or LED load fail short will be
automatically disabled instead of wasting the programmed output current. The test current in the
AAT3123A is higher (~150µA) to accommodate
LEDs with lower impedance in failure mode.
Thermal Protection
The AAT3123/23A/24 has a thermal protection circuit
that will shut down the internal LDO and charge pump
if the die temperature rises above the thermal limit, as
is the case during a short-circuit of the OUT pin.
Driving Multiple LEDs, White LED
Display Module Backlights, and
Individual LEDs Connected in Parallel
The AAT3123/23A/24 D1 to D6 outputs are true
constant current sources capable of driving up to
20mA each over the operation input voltage range.
Since these outputs are true constant current
sources, they may be connected in parallel to drive
a single power output. Any combination of outputs
(D1 to D6) may be connected in parallel. The maximum total output current is a sum of how many
current sources are parallel connected. This feature is particularly useful to power pre-manufac11
AAT3123/23A/24
High Efficiency 1X/1.5X Fractional Charge
Pump for White LED Applications
tured display modules which are pre-wired with
white LED backlights connected in a parallel circuit
configuration. Any combination of outputs may be
connected in parallel to drive groups of LEDs. The
AAT3123 internal current source reference circuit
bases feedback from current sensed on the D1
output. The AAT3124 internal current source reference circuit bases feedback from current sensed
on the D1 and D5 outputs. For best operation, the
only requirement for this type of application is the
output D1 (and/or D5 for the AAT3124) should
always be connected to the load circuit.
The AAT3124 may be used to drive multiple LEDs
having differing forward voltages. Using feedback
techniques, the current in D1 to D4 output current
sources are referenced to the current in the LED
connected to D1. In the AAT3124 (six-output version), the D5 and D6 output current sources are
referenced to the current in D5, not to D1. If all six
LEDs are of similar type, the diodes will be
matched in current, maintaining uniform LED
brightness despite variations in manufacturer, production, etc.
However, if the diodes are dramatically different in
type comprising a mix of high-VF and low-VF LEDs,
the AAT3124 has the capability to optimally and
simultaneously drive up to four LEDs of one type
and up to two LEDs of another type. Such a feature
can be useful for driving different color LEDs; driving both display backlight and photo-flash LEDs; or
for driving main-LCD and sub-LCD display LED
backlights from a single charge pump IC.
For example, when driving independent RGB LEDs,
the green and blue LEDs typically require a high VF
to operate (e.g., 3.7V), while the red LED needs a
low forward voltage (e.g., 2V). By connecting the
green and blue diodes to outputs D1 to D4 and the
red diodes to D5 and D6, good control and uniformity in brightness are maintained despite the 2V difference in the diode forward voltages. The AAT3124
determines if the 1.5X charge pump circuit is needed based on the voltage on D1 and D5, whichever
12
is higher. If adequate voltage is available to drive
the higher voltage LED (of output D1 or D5) without
the charge pump running, the IC automatically
switches into step-down (1X) mode to maximize
efficiency.
Similarly, if a 4V photo-flash LED array is connected to outputs D1 through D4 (with the outputs
shorted together) and two 3.3V sub-LCD-display
backlight LEDs are connected to outputs D5 and
D6, then the AAT3124 can optimally drive each set
of LEDs at the programmed current level (see
application schematics). The photo flash can be
disabled by an N-channel switch connected in
series with the photo-flash LED.
The AAT3123/23A/24 has only one programmed
value of current and does not allow for separate
on/off or brightness control of each current source
output. This limitation can easily be circumvented
by introducing grounded source N-channel MOSFET switches in series with the LEDs to turn any
given LED (or bank of LEDs) on or off. The various
LEDs can be turned on and off independently,
simultaneously, or multiplexed to produce any variety of lighting effects. By reprogramming the current source (via the serial interface) between
switching transitions, the brightness of individual
LEDs or banks of LEDs can also be controlled.
Charge Pump Compatibility
The four-output AAT3123 is pin compatible with the
AAT3113 in both QFN and TSOPJW packages.
The six-output AAT3124 is pin compatible with the
AAT3114 in the QFN package. Compared to the
AAT3113/14, the AAT3123/23A/24 offers an
improved overall efficiency, wider operating range,
and the ability to drive high-VF LEDs (up to 4.3V) at
full current from a 3V input condition. The
AAT3123/23A/24 is well suited for battery-powered
applications using single-cell lithium-ion (li-ion) batteries (4.2V to 2.8V), lithium-polymer batteries, and
3-series connected dry cells (3.6V).
3123.2005.12.1.4
AAT3123/23A/24
High Efficiency 1X/1.5X Fractional Charge
Pump for White LED Applications
Additional Application Circuits
VIN
C1+
C1
1µF
VBATTERY
C1C2+
VOUT
CIN
C OUT
1µF
1µF
AAT3123
AAT3123A
C2
1µF
C2-
EN/SET
EN/SET
D1
D2
D3
D4
GND
D4
D3
D2
D1
Typical AAT3123/23A Application Circuit.
VIN
C1+
C1
1µF
C1C2+
VOUT
VBATTERY
CIN
1µF
C OUT
1µF
AAT3123
AAT3123A
C2
1µF
C2D1
D2
D3
D4
EN/SET
Display Module
EN/SET
D1
D2
D3
D4
GND
RB1
RB2
RB3
RB4
Resistor R is optional
AAT3123/23A Driving a Display Module with Four Paralleled White LEDs.
3123.2005.12.1.4
13
AAT3123/23A/24
High Efficiency 1X/1.5X Fractional Charge
Pump for White LED Applications
VIN
C1+
C1
1µF
CIN
C OUT
1µF
1µF
D2
D3
D4
RB1
RB2
RB3
RB4
C1C2+
VOUT
VBATTERY
D1
C2
1µF
AAT3124
C2-
EN/SET
Resistor R is optional
D1
D2
D3
D4
D5
D6
EN/SET
D5
D6
GND
RB5
RB6
Resistor R is optional
AAT3124 Driving Two Groups of Paralleled White LEDs (e.g., main and sub-LCD backlights).
VIN
C1+
C1
1µF
C1C2+
VOUT
VBATTERY
CIN
C OUT
1µF
1µF
C2
1µF
AAT3124
C2-
EN/SET
EN/SET
D1
D2
D3
D4
D5
D6
D1
D2
D3
D4
D5
D6
RB1*
RB2*
RB3*
RB4*
RB5*
RB6*
GND
Photo-Flash LED
Resistor R is optional
*In some applications, white LED forward voltages (VF) can vary significantly. Ballast resistors between the LED cathodes and ground are recommended
for balancing the forward voltage differences. The ballast resistor value may be approximated by the following equation:
RB =
VSOURCE - VF
IF
AAT3124 Driving a High-Current Photo-Flash LED.
14
3123.2005.12.1.4
AAT3123/23A/24
High Efficiency 1X/1.5X Fractional Charge
Pump for White LED Applications
VIN
C1+
C1
1µF
C1C2+
VOUT
VBATTERY
CIN
COUT
1µF
1µF
AAT3124
C2
1µF
C2-
EN/SET
EN/SET
D1
D2
D3
D4
D5
D6
D1
D2
D3
D4
GND
D5
D6
Enable Display Backlight
Enable Keyboard Backlight
AAT3124 Driving Two Groups of Paralleled White LEDs (with series N-channel switch).
VIN
C1+
C1
1µF
C1C2+
VOUT
VBATTERY
CIN
C OUT
1µF
1µF
AAT3124
C2
1µF
C2-
EN/SET
EN/SET
D1
D2
D3
D4
D5
D6
GND
RED1
RED2
GRN1
GRN2
BLU1
BLU2
Enable Red
Enable Green
Enable Blue
AAT3124 Separately Driving RGB Color LEDs.
3123.2005.12.1.4
15
AAT3123/23A/24
High Efficiency 1X/1.5X Fractional Charge
Pump for White LED Applications
Additional Application Circuits
VIN
C1+
C1
1µF
C1C2+
VOUT
VBATTERY
CIN
1µF
COUT
1µF
AAT3124
C2
1µF
C2-
EN/SET
EN/SET
D1
D2
D3
D4
D5
D6
Common-Anode
RGB Color LED
GND
RED
GRN
BLU
Enable Red
Enable Green
Enable Blue
AAT3124 Driving Common-Anode RGB Color LED.
16
3123.2005.12.1.4
AAT3123/23A/24
High Efficiency 1X/1.5X Fractional Charge
Pump for White LED Applications
Ordering Information
Package
Marking1 Part Number (Tape and Reel)2
TSOPJW-12
TSOPJW-12
IRXYY
OIXYY
AAT3123ITP-20-T1
AAT3123AITP-20-T1
QFN44-16
ISXYY
AAT3124ISN-20-T1
Description
4-Channel Output
4-Channel Output with Increased Start-Up
Current (see “Test Current/Channel Disable”
section on page 11)
6-Channel Output
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°
0.010
0.45 ± 0.15
All dimensions in millimeters.
1. XYY = assembly and date code.
2. Sample stock is generally held on all part numbers listed in BOLD.
3123.2005.12.1.4
17
AAT3123/23A/24
High Efficiency 1X/1.5X Fractional Charge
Pump for White LED Applications
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.
© 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
18
3123.2005.12.1.4