202137A.pdf

DATA SHEET
AAT3132
High Efficiency 1.5X Fractional Charge Pump for White LED Applications
General Description
Features
The AAT3132/32A is a low noise, constant frequency
charge pump DC/DC converter that uses fractional
(1.5X) conversion to maximize efficiency for white LED
applications. The device can be used to produce current
levels up to 20mA in three of its outputs and up to 25 or
30mA in one of its outputs to drive 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) makes the AAT3132/32A ideally suited for small battery-powered applications.
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Skyworks' Simple Serial Control™ (S2Cwire™) interface
is used to enable, disable, and set the LED drive current
in two groups: the three 20mA outputs and the single
30mA output with multiple level logarithmic scales. The
AAT3132/32A 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
AAT3132/32A is available in the very small, Pb-free,
12-pin TSOPJW package.
VIN Range: 2.7V to 5.5V
<1.0µA of Shutdown Current
1MHz Switching Frequency
White LED Backlighting
Fully Independent Display Lighting
Drives Low-VF and High-VF Type LEDs
Up to Three 20mA Outputs
Single 25mA Output (AAT3132-1)
Single 30mA Output (AAT3132/32A)
Multi-Position Logarithmic Scale with Digital Control
Low Noise Constant Frequency Operation
Regulated Output Current
Automatic Soft Start
No Inductors
-40°C to +85°C Temperature Range
12-Pin TSOPJW Package
Applications
•
•
•
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Color (RGB) Lighting
Programmable Current Source
White LED Backlighting
White Photo Flash for Digital Still Cameras
Typical Application
VIN
C1+
C1
1µF
VOUT
VBATTERY
CIN
1µF
COUT
1µF
C1C2+
AAT3132
C2
1µF
C2D1
D2
D3
D4
EN/SET
EN/SET
D5
D4
D3
D2
D1
GND
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202137A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 5, 2012
1
DATA SHEET
AAT3132
High Efficiency 1.5X Fractional Charge Pump for White LED Applications
Pin Descriptions
Pin #
Symbol
1
2
3
4
5
6
7
8
9
10
11
12
C2+
OUT
C1C1+
D3
D2
D4
D1
EN/SET
IN
GND
C2-
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 #3.
Current source output #2.
Current source output #4.
Current source output #1.
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+
OUT
C1C1+
D3
D2
2
1
12
2
11
3
10
4
9
5
8
6
7
C2GND
IN
EN/SET
D1
D4
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202137A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 5, 2012
DATA SHEET
AAT3132
High Efficiency 1.5X Fractional Charge Pump for White LED Applications
Absolute Maximum Ratings1
Symbol
VIN
VOUT
VEN/SET
VEN/SET(MAX)
IOUT2
TJ
Description
Input Voltage
Charge Pump Output
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
VIN - 0.3
150
-40 to 150
V
V
V
V
mA
°C
Value
Units
160
625
°C/W
mW
Thermal Information3
Symbol
qJA
PD
Description
Thermal Resistance
Maximum Power Dissipation (TA = 25°C)4
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.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202137A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 5, 2012
3
DATA SHEET
AAT3132
High Efficiency 1.5X Fractional Charge Pump for White LED Applications
Electrical Characteristics1
VIN = 3.5V, CIN = COUT = C1 = C2 = 1.0µF; TA = -40°C to +85°C, unless otherwise noted. Typical values are TA = 25°C.
Symbol
Description
Input Power Supply
VIN
Operation Range
ICC
Operating Current
ISHDN
Shutdown Current
IDX
Maximum Output Current D1 to D3
IDX
Maximum Output Current D4
I(D-Match)
hCP
Charge Pump
TSS
FCLK
EN/SET
VEN(L)
VEN(H)
TEN/SET LO
TEN/SET HI
TOFF
Input Current
Conditions
Min
Typ
2.7
3.0 ≤ VIN ≤ 5.5, Active, No Load Current
EN = 0
3.0 ≤ VIN ≤ 5.5
TA = 25°C AAT3132-1
TA = 25°C AAT3132
1.8
18
22.5
27
20
25
30
Max
Units
5.5
3.5
1.0
22
27.5
33
V
mA
µA
mA
mA
Current Matching Between Any Two
Outputs
VD1:D3 = 3.6, VIN = 3.3V
0.5
%
Charge Pump Section Efficiency
VIN = 3.5V, IOUT(TOTAL) = 90mA, Measured
from IN to OUT
93
%
200
1000
µs
kHz
Section
Soft-Start Time
Clock Frequency
Enable Threshold Low
Enable Threshold High
EN/SET Low Time
Minimum EN/SET High Time
EN/SET Off Timeout
EN/SET Input Leakage
0.5
VEN/SET < 0.5
VEN/SET > 1.4
VEN/SET < 0.5
1.4
0.3
75
50
-1
500
1
V
V
µs
ns
µs
µA
1. The AAT3132/32A 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
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202137A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 5, 2012
DATA SHEET
AAT3132
High Efficiency 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.
IDIODE vs. Input Voltage
VIH and VIL vs. VIN
(4x20mA)
90
VDIODE = 3.3V
85
VDIODE = 3.4V
IDIODE (mA)
80
0.850
VDIODE = 3.5V
VDIODE = 3.6V
0.825
0.800
75
0.775
70
0.750
65
0.725
60
0.700
55
0.675
50
0.650
45
0.625
40
0.600
2.7
2.9
3.1
3.3
3.5
3.7
3.9
4.1
4.3
4.5
4.7
4.9
VIH
VIL
2.5
5.1
3.0
3.5
4.0
4.5
5.0
5.5
Input Voltage (V)
Input Voltage (V)
Turn-On to Full-Scale Load Switch
Turn-On to Full-Scale Charge Pump
ENSET
(1V/div)
ENSET
(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)
80mA Load Characteristics
Turn-Off
VIN
20mV/div
ENSET
(1V/div)
VDIODE
(2V/div)
IIN
(100mA/div)
OUT
VDIODE
Time (200µs/div)
Time (1µs/div)
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202137A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 5, 2012
5
DATA SHEET
AAT3132
High Efficiency 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.
Output Current Change (%)
I DIODE vs. Temperature
2.00
1.00
0.00
-1.00
-2.00
-3.00
-4.00
-5.00
-6.00
-7.00
-50
-30
-10
10
30
50
Temperature (°C)
6
70
90
110
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202137A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 5, 2012
DATA SHEET
AAT3132
High Efficiency 1.5X Fractional Charge Pump for White LED Applications
Functional Block Diagram
VIN
Soft-Start
Control
1.5X
Charge
Pump
1MHz
Oscillator
Voltage
Reference
C1+
C1C2+
C2OUT
Current
Reference
Quad
Output
DAC
D1
D2
D3
32x16 bit
ROM
EN/SET
S2Cwire
Interface
Single
Output
DAC
32x16 bit
ROM
D4
GND
Functional Description
The AAT3132/32A is a high efficiency (1.5X) fractional
charge pump device intended for white LED backlight
applications. It consists of a 1.5X charge pump with multiple current source outputs. To maximize power conversion efficiency, an internal feedback control sensing circuit monitors the voltage required on the constant current source outputs.
The AAT3132/32A 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 1.5X charge pump output is converted into three (D1 to D3) constant current outputs to
drive three individual LEDs with a maximum current of
20mA each, and one (D4) constant current output with
a maximum current of 25 or 30mA. The current source
output magnitude is controlled by the EN/SET serial data
interface. The interface records rising edges of the EN/
SET pin and decodes them into 32 addresses corresponding to individual current level settings. The 32
addresses are divided up such that outputs D1 to D3 can
be controlled independently of output D4. For Addresses
1 to 8, 9 to 16, 17 to 24, and 25 to 32, outputs D1 to D3
start at 0mA and increase from 0.5mA to 20mA in three
8dB steps and three 2.5dB steps. Output D4 remains
constant over these address ranges which provides
orthogonal control of the two channels. For Addresses 1
to 8, D4 is set to 0mA. For Addresses 9 to 16, D4 is set
to the next brightness setting; likewise for Addresses 17
to 24 and Addresses 25 to 32. This is summarized in
Table 1 and Figure 1.
The modulo 32 interface wraps back to State 1 after the
32nd clock. With each EN/SET pulse, the output current
changes to the next setting in the address decoding. To
change settings to the previous address decoding, 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 currents 0mA.
Additional clocks are required to set the desired current
level. 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.
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202137A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 5, 2012
7
DATA SHEET
AAT3132
High Efficiency 1.5X Fractional Charge Pump for White LED Applications
Applications Information
Current Level Settings (mA)
Address
D1 to D3
D4 (AAT3132/32A)
D4 (AAT3132-1)
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
0.0
0.5
1.3
3.3
8.3
11.1
15.0
20.0
0.0
0.5
1.3
3.3
8.3
11.1
15.0
20.0
0.0
0.5
1.3
3.3
8.3
11.1
15.0
20.0
0.0
0.5
1.3
3.3
8.3
11.1
15.0
20.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
15.0
15.0
15.0
15.0
15.0
15.0
15.0
15.0
30.0
30.0
30.0
30.0
30.0
30.0
30.0
30.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
15.0
15.0
15.0
15.0
15.0
15.0
15.0
15.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
20.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
25.0
Constant Current Output Level Settings
The constant current source output amplitude for outputs D1 to D3 and D4 are set via the serial interface
according to a logarithmic scale depicted in Figure 1.
Using a logarithmic scale, 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 AAT3132/32A is programmable through its S2Cwire 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.” Furthermore, with its high-speed
serial interface (1MHz data rate), the output current of
the AAT3132/32A 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.
Table 1: Constant Current Source Output
Programming Levels.
Output Current Level Settings
Option 3132
30
25
Current (mA)
20
15
10
5
0
32
31
30
29
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
Address Code
Figure 1: Output Current Level Settings (Option AAT3132).
8
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202137A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 5, 2012
DATA SHEET
AAT3132
High Efficiency 1.5X Fractional Charge Pump for White LED Applications
EN/SET Serial Interface (S2Cwire)
LED Selection
The current source output magnitude is controlled by the
EN/SET serial data interface. The interface records rising
edges of the EN/SET pin and decodes them into 32 individual current level settings, as summarized in Table 1.
The modulo 32 interface wraps back to State 1 after the
32nd clock, so the previous state is achieved by clocking
the EN/SET pin 31 times. The counter can be clocked at
speeds up to 1MHz, so that intermediate states are not
visible. The first rising edge of EN/SET enables the IC
and initially sets the output LED current to 0. 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.
The AAT3132/32A is specifically intended for driving
white LEDs. However, the device design will allow the
AAT3132/32A 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 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 AAT3132/32A 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 AAT3132/32A 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. Backinjected 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 AAT3132/32A soft-start feature
prevents noise transient effects associated with inrush
currents during start-up of the charge pump circuit.
EN/SET Timing Diagram
tHI
tOFF
tLO
EN/SET
Code
OFF
1
2
3
OFF
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202137A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 5, 2012
9
DATA SHEET
AAT3132
High Efficiency 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 AAT3132/32A, it is very difficult to measure
efficiency in terms of a percent value comparing input
power over output power.
Since the AAT3132/32A 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 components count,
reliability, operating range, and total energy usage...not
just % efficiency.
The AAT3132/32A 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. The efficiency (h) 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 (h) 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 (h) can be
rewritten as:
η=
POUT
VOUT ∙ IOUT
V
=
= OUT
PIN
VIN ∙ 1.5IOUT 1.5VIN
-or-
η(%) = 100
10
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 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 100mW. 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
AAT3132/32A. 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.
 VOUT 
 1.5VIN
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202137A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 5, 2012
DATA SHEET
AAT3132
High Efficiency 1.5X Fractional Charge Pump for White LED Applications
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 typically composed of X7R, X5R,
Z5U, or Y5V dielectric materials. Large ceramic capacitors, greater than 2.2µF, are often available in low-cost
Y5V and Z5U dielectrics, but capacitors greater than 1µF
are usually not required for AAT3132/32A 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 AAT3132A is higher (~150µA) to accommodate LEDs with lower impedance in failure mode.
Thermal Protection
The AAT3132/32A 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 OUT pin.
Driving Multiple LEDs, White LED Display Module Backlights, and Individual LEDs Connected in Parallel
The AAT3132/32A D1 to D4 outputs are true constant
current sources capable of driving up to 20mA (D1 to
D3) or 25/30mA (D4) 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
D4) 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-manufactured display modules which are prewired 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
AAT3132/32A internal current source reference circuit
bases feedback from current sensed on the D1 and D4
outputs. For best operation, the only requirement for
this type of application is the outputs D1 and D4 should
always be connected to the load circuit.
The AAT3132/32A may be used to drive multiple LEDs
having differing forward voltages. Using feedback techniques, the current in D1 to D3 is referenced to the current in the LED connected to D1. Current source output
D4 is its own reference. If all 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 type and low-VF type LEDs,
the AAT3132/32A has the capability to optimally drive
up to four LEDs of one type and up to two LEDs of
another type simultaneously. This feature can be useful
for driving different color LEDs, driving both display
backlight and photo-flash LEDs, or for driving main 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 D3 and the red diodes to
D4, good control and uniformity in brightness is maintained despite the 2V difference in the diode forward
voltages.
Similarly, if a 4V photo-flash LED array is connected to
outputs D1 through D3 (with the outputs shorted
together) and two 3.3V sub-LCD display backlight LEDs
are connected to output D4, then the AAT3132/32A can
optimally drive each set of LEDs at the programmed current level (see Figure 2).
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
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11
DATA SHEET
AAT3132
High Efficiency 1.5X Fractional Charge Pump for White LED Applications
VIN
C1+
C1
1µF
VOUT
VBATTERY
CIN
COUT
1µF
1µF
C1C2+
AAT3132
AAT3132A
C2
1µF
D1
D2
D3
D5
D6
D4
C2D1
D2
D3
EN/SET
EN/SET
GND
D4
Figure 2: AAT3132/32A Driving Two Groups of Paralleled White LEDs
(e.g., main and sub-LCD backlights).
12
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202137A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 5, 2012
DATA SHEET
AAT3132
High Efficiency 1.5X Fractional Charge Pump for White LED Applications
Ordering Information
Package
Marking1
Part Number (Tape and Reel)2
TSOPJW-12
TSOPJW-12
TSOPJW-12
JAXYY
KHXYY
OJXYY
AAT3132ITP-T1
AAT3132ITP-1-T1
AAT3132AITP-1-T1
Skyworks Green™ products are compliant with
all applicable legislation and are halogen-free.
For additional information, refer to Skyworks
Definition of Green™, document number
SQ04-0074.
Package Information
TSOPJW-12
2.85 ± 0.20
2.40 ± 0.10
0.20 + 0.10
- 0.05
0.50 BSC 0.50 BSC 0.50 BSC 0.50 BSC 0.50 BSC
7° NOM
0.055 ± 0.045
All dimensions in millimeters.
0.04 REF
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
1. XYY = assembly and date code.
2. Sample stock is generally held on part numbers listed in BOLD.
Copyright © 2012 Skyworks Solutions, Inc. All Rights Reserved.
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Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202137A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 5, 2012
13