1
AAT3104
DATA SHEET
Low Cost 1x/2x Four-Channel Charge Pump WLED Driver
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202124A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 2, 2012
General Description
The AAT3104 is a charge-pump based, current-source
white LED driver capable of driving one to four LEDs up
to 30mA, each. It automatically switches between 1x
mode and 2x mode to maintain the highest efficiency
and optimal LED current accuracy and matching.
The AAT3104 charge pump’s 1x mode (bypass mode)
has very low resistance allowing LED current regulation
to be maintained with input supply voltage approaching
the LED forward voltage.
LED brightness is controlled using Skyworks' patented
S2Cwire™ single wire interface. The AAT3104 is available
in a 2x2mm 10-lead SC70JW-10 package.
Features
• Drives up to 4 LEDs at up to 31mA each
• Automatic Switching Between 1x and 2x Modes
• 1MHz Switching Frequency
• Linear LED Output Current Control
• Single-wire, S2Cwire Interface
AAT3104-1: 16-step
AAT3104-2: 32-step
• ±10% LED Output Current Accuracy
• ±3% LED Output Current Matching
• Low-current Shutdown Mode
• Built-in Thermal Protection
• Automatic Soft-start
• Available in 2x2mm SC70JW-10 Package
Applications
• Cordless Phone Handsets
• Digital Cameras
• Mobile Phone Handsets
• MP3 and PMP Players
Typical Application
Input Voltage
2.7V to 5.5V
EN/SET
S2Cwire
Interface
IN
C+
C-
EN/SET
OUT
D1
D2
D3
COUT
1µF
GND
AAT3104
CP
1µF
CIN
1µF
D4
2
AAT3104
DATA SHEET
Low Cost 1x/2x Four-Channel Charge Pump WLED Driver
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202124A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 2, 2012
Pin Descriptions
Pin# Name Description
1 D2 LED2 Current Source Output. D2 is the output of LED2 current source. Connect LED2’s anode to D2
and its cathode to GND.
2 D1 LED1 Current Source Output. D1 is the output of LED1 current source. Connect LED1’s anode to D1
and its cathode to GND.
3 OUT Charge Pump Output. OUT is the output of the charge pump. Bypass OUT to GND with a 1μF or
larger ceramic capacitor.
4C- Charge Pump Capacitor Negative Node.
5 C+ Charge Pump Capacitor Positive Node. Connect a 1μF ceramic capacitor between C+ and C-.
6 GND Analog Ground. Connect this pin to the system’s analog ground plane.
7 EN/SET LED Enable and serial control input. EN/SET is the ON/OFF control for the LED and the S2Cwire digital
input for the AAT3104-1/-2 to control serially the LED brightness according to the maximum current.
8 IN Power source input. Connect IN to the power source, typically the battery. Bypass IN to GND with a
1μF or larger ceramic capacitor.
9 D4 LED4 Current Source Output. D4 is the output of LED4 current source. Connect LED4’s anode to D4
and its cathode to GND.
10 D3 LED3 Current Source Output. D3 is the output of LED3 current source. Connect LED3’s anode to D3
and its cathode to GND.
Pin Configuration
SC70JW-10
(Top View)
D1
C-
C+
D3
D4
EN/SET
GND
D2 1
2
3
56
OUT IN
47
8
9
10
3
AAT3104
DATA SHEET
Low Cost 1x/2x Four-Channel Charge Pump WLED Driver
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202124A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 2, 2012
Absolute Maximum Ratings1
Symbol Description Value Units
VIN, VOUT
, VC+,
VC-, VD1...4
IN, C+, C-, OUT, D1, D2, D3, and D4 Pin Voltages to GND -0.3 to 6.0 V
VEN/SET EN/SET Pin Voltage to GND -0.3 to VIN + 0.3 V
TSStorage Temperature Range -65 to 150 °C
TJOperating Junction Temperature Range -40 to 150 °C
TLEAD Maximum Soldering Temperature (at leads, 10 sec) 300 °C
Thermal Information
Symbol Description Value Units
PDMaximum Power Dissipation2, 3 625 mW
θJA Maximum Thermal Resistance3160 °C/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. Mounted on an FR4 circuit board.
3. Derate 6.25mW/°C above 40°C ambient temperature.
4
AAT3104
DATA SHEET
Low Cost 1x/2x Four-Channel Charge Pump WLED Driver
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202124A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 2, 2012
Electrical Characteristics1
IN = EN = 3.6V, CIN = 1µF, COUT = 1µF, C1 = 1µF, TA = -40°C to 85°C unless otherwise noted. Typical values are at TA
= 25°C.
Symbol Description Conditions Min Typ Max Units
Input Power Supply
VIN Input Voltage Range 2.7 5.5 V
IqQuiescent Current IN = 5.5V, EN = IN, VD1 = VD2 = VD3 = 0V 6 mA
IIN No Load Operating Current
IN = 5.5V, EN = IN, ID1 = ID2 = ID3 = ID4
= FS, VD1 = VD2 = VD3 = VD4 = IN – 1.5V,
Exclude IDN current, 1x mode
3.5 mA
Operating, ID1 = ID2 = ID3 = ID4 = OPEN,
2x mode 6 mA
IIN(SHDN) Input Shutdown Current EN/SET = GND 1 μA
Charge Pump Section
IOUT OUT Maximum Output Current 150 mA
VOUT Charge Pump Output Voltage When charge pump is on 5 V
fOSC Charge Pump Oscillator Frequency 0.6 0.8 1.05 MHz
VIN_(TH) Charge Pump Mode Hysteresis ID1 = ID2 = ID3 = ID4 =30mA 150 250 mV
tOUT LED Output Current Start-up Time EN/SET =IN 190 μs
AAT3104-1/-2: LED Current Source Outputs
ID_(MAX)
D1 – D4 Current Accuracy
(AAT3104-1 only) DATA = 1, VIN – VF = 1.5V 27 30 33 mA
ID_(MAX)
D1 – D4 Current Accuracy
(AAT3104-2 only) DATA = 1, VIN – VF = 1.5V 28 31 34 mA
ΔID_(MAX) D1 – D4 Current Matching DATA = 1, VIN – VF = 1.5V ±3 %
ID_(DATA15)
D1 – D4 Current Accuracy
(AAT3104-1 only) DATA = 15, VIN – VF = 1.5V 1.6 2.0 2.4 mA
ID_(DATA29)
D1 – D4 Current Accuracy
(AAT3104-2 only) DATA = 29, VIN – VF = 1.5V 1.6 2.0 2.4 mA
VD_(TH)
D1- D4 Charge Pump Mode Transition
Threshold
ID1 = ID2 = ID3 = ID4 = 30mA, VIN – VD1 is
measured 380 mV
ID1 = ID2 = ID3 = ID4 = 20mA, VIN – VD1 is
measured 350 mV
AAT3104-1/-2: EN/SET and S2Cwire Control
VENH EN/SET Input High Threshold Voltage 1.4 V
VENL EN/SET Input Low Threshold Voltage 0.4 V
IEN(LKG) EN/SET Input Leakage Current EN/SET = IN = 5V -1 1 μA
tEN/SET(OFF) EN/SET Input OFF Timeout 500 µs
tEN/SET(LAT) EN/SET Input Latch Timeout 500 µs
tEN/SET(LOW) EN/SET Input Low Time 0.3 75 µs
tENSET(H-MIN) EN/SET Minimum High Time 50 ns
tENSET(H-MAX) EN/SET Maximum High Time 75 µs
1. The AAT3104 is guaranteed to meet performance specification over the -40°C to 85°C operating temperature range and are assured by design, characterization and correlation
with statistical process controls.
5
AAT3104
DATA SHEET
Low Cost 1x/2x Four-Channel Charge Pump WLED Driver
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202124A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 2, 2012
Typical Characteristics
VIN = 3.6V, CIN = COUT = C1 = 1μF; TA = 25°C, unless otherwise noted.
1X Mode Turn-On Waveform
(VIN = 4.2V; Load = 120mA)
Time (200µs/div)
EN
(1V/div)
VLED
(2V/div)
IIN
(200mA/div)
VOUT
(2V/div)
0
0
0
0
2X Mode Turn-On Waveform
(VIN = 3.6V; Load = 120mA)
Time (200µs/div)
EN
(1V/div)
VLED
(2V/div)
IIN
(250mA/div)
VOUT
(2V/div)
0
0
0
0
2X Mode Turn-Off Waveform
(VIN = 3.6V; Load = 120mA)
Time (200µs/div)
EN
(1V/div)
VLED
(2V/div)
IIN
(250mA/div)
0
0
0
2X Mode Output Ripple
(VIN = 3.6V; Load = 120mA)
Time (0.4µs/div)
VOUT
(AC Coupled)
(20mV/div)
VIN
(AC Coupled)
(5mV/div)
0
0
1mA to 30mA LED Current Step
(VIN = 4.2V)
Time (80µs/div)
VLED
2V/div
IIN
200mA/div
VOUT
2V/div
EN
1V/div
0
0
0
0
30mA to 1mA LED Current Step
(VIN = 4.2V)
Time (80µs/div)
VLED
(2V/div)
IIN
(200mA/div)
VOUT
(2V/div)
EN
(1V/div)
0
0
0
0
6
AAT3104
DATA SHEET
Low Cost 1x/2x Four-Channel Charge Pump WLED Driver
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202124A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 2, 2012
Typical Characteristics
VIN = 3.6V, CIN = COUT = C1 = 1μF; TA = 25°C, unless otherwise noted.
Current Matching vs. Temperature
(AAT3104-2; Code = 1)
Temperature (°C)
Current (mA)
29.0
29.5
30.0
30.5
31.0
31.5
32.0
32.5
33.0
-40-15 10 35 60 85
D1
D2
D3
D4
Efficiency vs. Input Voltage
(ILED = 31mAx4; Voltage Sweep Upwards)
Input Voltage (V)
Efficiency (%)
30
40
50
60
70
80
90
2.73.1 3.53.9 4.34.7 5.15.5
VF = 2.7V
VF = 3.0V
VF = 3.3V
VF = 3.6V
Efficiency vs. Input Voltage
(ILED = 31mAx4; Voltage Sweep Downwards)
Input Voltage (V)
Efficiency (%)
30
40
50
60
70
80
90
2.73.1 3.53.9 4.34.7 5.15.5
VF = 2.7V
VF = 3.0V
VF = 3.3V
VF = 3.6V
Quiescent Current vs. Input Voltage
Input Voltage (V)
Quiescent Current (mA)
2.73.1 3.53.9 4.34.7 5.15.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
6.5
85°C
25°C
-40°C
Shutdown Current vs. Temperature
Temperature (°C)
ShutdownnCurrent (nA)
-40-15 10 35 60 85
0
5
10
15
20
25
VIN = 5.5V
VIN = 2.7V
Frequency vs. Temperature
Temperature (°C)
Frequency (KHz)
-40-15 10 35 60 85
750
760
770
780
790
800
810
820
830
840
850
7
AAT3104
DATA SHEET
Low Cost 1x/2x Four-Channel Charge Pump WLED Driver
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202124A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 2, 2012
Typical Characteristics
VIN = 3.6V, CIN = COUT = C1 = 1μF; TA = 25°C, unless otherwise noted.
No Load Operating Current vs. Input Voltage
(2x Mode)
Input Voltage (V)
Operating Current (mA)
2.73.1 3.53.9 4.34.7 5.15.5
5.0
5.2
5.4
5.6
5.8
6.0
6.2
6.4
85°C
25°C
-40°C
EN Input High Threshold Voltage
vs. Input Voltage
Input Voltage (V)
V
EN(H)
(V)
2.73.1 3.53.9 4.34.7 5.15.5
0.2
0.4
0.6
0.8
1.0
1.2
85°C
25°C
-40°C
EN Input Low Threshold Voltage
vs. Input Voltage
Input Voltage (V)
V
EN(L)
(V)
2.73.1 3.53.9 4.34.7 5.15.5
0.2
0.4
0.6
0.8
1.0
1.2
85°C
25°C
-40°C
EN/SET Input Latch Timeout
vs. Input Voltage
Input Voltage (V)
T
EN/SET(LAT)
(µs)
2.73.1 3.53.9 4.34.7 5.15.5
150
180
210
240
270
300
330
85°C
25°C
-40°C
EN/SET Input OFF Timeout
vs. Input Voltage
Input Voltage (V)
T
EN/SET(OFF)
(µs)
2.73.1 3.53.9 4.34.7 5.15.5
150
200
250
300
350
400
85°C
25°C
-40°C
8
AAT3104
DATA SHEET
Low Cost 1x/2x Four-Channel Charge Pump WLED Driver
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202124A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 2, 2012
Functional Description
The AAT3104 is a low-cost charge-pump solution
designed to drive up to four white LEDs. The charge
pump operates from a 2.7V to 5.5V power source and
converts it to voltage levels necessary to drive the LEDs.
LED current is individually controlled through integrated
current sources powered from the output of the charge
pump. Low 1x charge-pump output resistance and low-
drop voltage current sources allow the charge pump to
remain in 1x mode with an input voltage as low as 3.8V
and LED forward voltages of 3.5V. Once in 2x mode, the
charge pump monitors the input supply voltage and
automatically switches back to 1x mode when there is
sufficient input voltage.
The AAT3104 requires only three external components:
one 1μF ceramic capacitor for the charge pump flying
capacitor (CP), one 1μF ceramic input capacitor (CIN), one
1μF ceramic output capacitor (COUT). The four constant
current outputs of the AAT3104 (D1 to D4) can drive four
individual LEDs with a maximum current of 30mA each.
Skyworks' S2Cwire serial interface enables the AAT3104-
1/-2 and changes the current source magnitudes through
the EN/SET pin.
S2Cwire Serial Interface
The LED output current of the AAT3104 is controlled by
Skyworks' S2Cwire serial interface. Since the LED current
is programmable, no PWM 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.” With its high-speed serial interface
(1MHz data rate), the LED current can be changed quick-
ly and easily. Also, the non-pulsating LED current reduc-
Functional Block Diagram
C–C+ OUT
GND
IN
D3
D2
D1
S
2
Cwire Control5 Bits DAC
EN/SET
D4
Two-Mode
CP Control
V
F
Monitoring
4
I
REF
5
1x
2x
9
AAT3104
DATA SHEET
Low Cost 1x/2x Four-Channel Charge Pump WLED Driver
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202124A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 2, 2012
es system noise and improves LED reliability. The S2Cwire
interface relies on the number of rising edges to the EN/
SET pin to set the register. A typical write protocol is a
burst of EN/SET rising edges, followed by a pause with
EN/SET held high for at least tLAT (500μs). The pro-
grammed current is then seen at the current source out-
puts. When EN/SET is held low for an amount of time
longer than tOFF (500μs), the AAT3104 enters into shut-
down mode and draws less than 1μA from the input and
the internal data register is reset to zero.
The AAT3104-1/2’s serial interface reduces the LED cur-
rent on each rising pulse of the enable input. If the
AAT3104 is in shutdown, the first rising edge of the EN/
SET input turns on the LED driver to the maximum cur-
rent. Successive rising edges decrease the LED current
as shown in Table 1 and Figure 2 for the AAT3104-1. For
the AAT3104-2, Table 2 and Figure 3 illustrate a 32-step
LED current control profile.
Data
EN Rising
Edges
D1-D4
Current (mA)
1 1 30
2 2 28
3 3 26
4 4 24
5 5 22
6 6 20
7 7 18
8 8 16
9 9 14
10 10 12
11 11 10
12 12 8
13 13 6
14 14 4
15 15 2
16 16 0.5
Table 1: AAT3104-1 LED Current Settings.
Data EN Rising Edges D1-D4 Current (mA)
1 1 31
2 2 30
3 3 29
4 4 28
5 5 27
6 6 26
7 7 25
8 8 24
9 9 23
10 10 22
11 11 21
12 12 20
13 13 19
14 14 18
15 15 17
16 16 16
17 17 15
18 18 14
19 19 13
20 20 12
21 21 11
22 22 10
23 23 9
24 24 8
25 25 7
26 26 6
27 27 5
28 28 4
29 29 3
30 30 2
31 31 1
32 32 0.5
Table 2: AAT3104-2 LED Current Settings.
2 3OF
FO
FF
t
LO
t
OFF
t
HI
1
Figure 1: EN/SET Timing Diagram.
10
AAT3104
DATA SHEET
Low Cost 1x/2x Four-Channel Charge Pump WLED Driver
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202124A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 2, 2012
Applications Information
LED Selection
The AAT3104 is specifically designed for driving white
LEDs. However, the device design will allow the AAT3104
to drive most types of LEDs with forward voltage speci-
fications ranging from 2.2V to 4.7V. LED applications
may include mixed arrangements for display backlight-
ing, keypad display, and any other application needing a
constant current source generated from a varying input
voltage. Since the D1 to D4 constant current sources are
matched with negligible supply voltage dependence, the
constant current channels will be matched regardless of
the specific LED forward voltage (VF) levels.
The low dropout current sources in the AAT3104 maxi-
mize performance and make it capable of driving LEDs
with high forward voltages. Multiple channels can be
combined to obtain a higher LED drive current without
complication.
All unused LED source pins should be connected to GND
or left floating. Do not connect to the OUT pin.
Device Switching Noise Performance
The AAT3104 operates at a fixed frequency of approxi-
mately 1MHz to control noise and limit harmonics that
can interfere with the RF operation of mobile communi-
cation 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 AAT3104
soft-start feature prevents noise transient effects associ-
ated with inrush currents during start-up of the charge
pump circuit.
Shutdown
Since the current switches are the only power returns for
all loads, there is no leakage current when all source
switches are disabled. To enter shutdown operation, the
EN/SET input for the AAT3104-1/2 should be strobed
low. After tOFF (500μs), AAT3104 will be shut down and
typically draws less than 1μA from the input. Registers
are reset to 0 in shutdown.
Power Efficiency and Device Evaluation
The charge pump efficiency discussion in the following
sections accounts only for efficiency of the charge pump
section itself. Due to the unique circuit architecture and
design of the AAT3104, it is very difficult to measure
efficiency in terms of a percent value comparing input
power over output power.
Since the AAT3104 outputs are pure constant current
sources and typically drive individual loads, it is difficult
to measure the output voltage for a given output 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 output power over input power efficiency.
The AAT3104 efficiency may be quantified under very
specific conditions and is dependent upon the input volt-
age versus the output voltage across the loads applied
S2C Wire Interface Data Code
Dx Output Current (mA)
0
7.5
15.0
22.5
30.0
12
34
5678910111213141
51
6
S2C Wire Interface Data Code
Dx Output Current (mA)
0
5
10
15
20
25
30
135791113151719212325272931
Figure 2: AAT3104-1 Current Control Profile. Figure 3: AAT3104-2 Current Control Profile.
11
AAT3104
DATA SHEET
Low Cost 1x/2x Four-Channel Charge Pump WLED Driver
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202124A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 2, 2012
to outputs D1 through for a given constant current set-
ting. Depending on the combination of VIN and voltages
sensed at the current sources, the device will operate in
load switch mode. When any one of the voltages sensed
at the current sources nears dropout, the device will
operate in 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.
1X Mode Efficiency
The AAT3104 1X mode is operational at all times and
functions alone to enhance device power conversion effi-
ciency when VIN is higher than the voltage across the
load. When in 1X mode, voltage conversion efficiency is
defined as output power divided by input power.
An expression for the ideal efficiency (η) in 1X charge-
pump mode can be expressed as:
P
OUT
PIN
V
F
· I
LED
VIN · IIN
V
F
· I
LED
VIN · IOUT
V
F
VIN
η = = = ≈
-or
V
F
VIN
η (%) = · 100
For a charge pump led driver with VF of 3.2V and 4.2V
input voltage, the theoretical efficiency is 76%. Due to
internal switching losses and IC quiescent current con-
sumption, the actual efficiency can be measured at 73%.
2X Charge Pump Mode Efficiency
The AAT3104 contains a charge pump which will boost
the input supply voltage in the event where VIN is less
than the voltage required to supply the output. The effi-
ciency (η) can be simply defined as a linear voltage
regulator with an effective output voltage that is equal to
one and two times the input voltage. Efficiency (η) for an
ideal 2X charge pump can typically be expressed as the
output power divided by the input power.
η =
P
F
PIN
In addition, with an ideal 2X charge pump, the output
current may be expressed as 1/3 of the input current.
The expression to define the ideal efficiency (η) can be
rewritten as
P
OUT
PIN
V
F
· I
LED
VIN · IIN
V
F
· I
LED
VIN · 2 · IOUT
V
F
2 · VIN
η = = = ≈
or
V
F
2 · VIN
η (%) = · 100
For a charge pump current source driver with VF of 3.2V
and 2.7V input voltage, the theoretical efficiency is 59%.
Due to internal switching losses and IC quiescent current
consumption, the actual efficiency can be measured at
57%. Efficiency will decrease substantially as load cur-
rent drops below 1mA or when the voltage level at VIN
approaches the voltage level at VOUT
.
Additional Applications
The current sources of the AAT3104 can be combined
freely to drive higher current levels through one LED. As
an example, a single LED can be driven at 120mA by
combining together D1 through D4 outputs.
For lower-cost applications, the flying capacitor can be
removed; C+ and C- should be floating. This will force
AAT3104 to operate in 1X mode. To maintain regulated
LED current, the input supply voltage has to be higher
than the charge-pump's dropout voltage in 1X mode plus
the forward voltage of the LED at the preset LED
current.
Capacitor Selection
Careful selection of the three external capacitors CIN, CP
,
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 constant 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
AAT3104. Ceramic capacitors offer many advantages
over their tantalum and aluminum electrolytic counter-
parts. 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 maximizing
charge pump transient response. Since ceramic capaci-
tors are non-polarized, they are not prone to incorrect
connection damage.
12
AAT3104
DATA SHEET
Low Cost 1x/2x Four-Channel Charge Pump WLED Driver
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202124A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 2, 2012
Input Voltage
2.7V to 5.5V
EN/SET
S2Cwire
Interface
IN
C+
C-
EN/SET
OUT
D1
D2
D3
COUT
1µF
GND
AAT3104
CP
1µF
CIN
1µF
D4
Figure 4: Higher Current, Single LED Application.
Input Voltage
> VF + VDROP
EN/SET
S2Cwire
Interface
IN
C+
C-
EN/SET
OUT
D1
D2
D3
COUT
1µF
GND
AAT3104
CIN
1µF
D4
Figure 5: Lower Cost 1X Mode Application.
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 connec-
tions, size or area, material composition, and ambient
temperature. Capacitor ESR is typically measured in mil-
liohms 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 gen-
erally have tight tolerance and are very stable over tem-
perature. Larger capacitor values are usually composed
of X7R, X5R, Z5U, or Y5V dielectric materials. Large
ceramic capacitors (i.e., larger than 2.2μF) are often
available in low cost Y5V and Z5U dielectrics, but capac-
itors larger than 1μF are not typically required for
AAT3104 applications. Capacitor area is another con-
tributor 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.
Evaluation Board Layout
When designing a PCB for the AAT3104, the key require-
ments are:
1. Place two flying capacitors C1 and C2 as close to the
chip as possible; otherwise 2x mode performance
will be compromised.
2. Place input and output decoupling capacitors as
close to the chip as possible to reduce switching
noise and output ripple.
13
AAT3104
DATA SHEET
Low Cost 1x/2x Four-Channel Charge Pump WLED Driver
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202124A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 2, 2012
Evaluation Board Schematic
1µF
C1
1µF
C2
1µF
C3
0.1µ F
C4
1K
R5
330
R7
JP2
20K
R2
VIN
JP5
EN
S2C
UP
S1
DOWN
S2
CYCLE
S3
S1
S2
S3
EN
OUT
C-
C+
IN
330
R6
4.7µF
C6
JP3JP4
123
J1
DC+
DC+
DC-
1K
R4
1K
R3
VDD
1
GP5
2
GP4
3
GP3
4GP25
GP16
GP07
VSS8
PIC12F675
U2
D1D2D4
Green
S2C
LED1
Red
MCU Power
LED2
POT10K
VR1
10uF
C
AAT3104
D2
1
D1
2
OUT
3
C-
4EN/SET 7
VIN8
D4 9
D3 10
GND6
C+
5
U1
D3
JP1
Figure 6: AAT3104 Evaluation Board Schematic.
Figure 7: AAT3104 Evaluation Board Figure 8: AAT3104 Evaluation Board
Top Layer. Bottom Layer.
14
AAT3104
DATA SHEET
Low Cost 1x/2x Four-Channel Charge Pump WLED Driver
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202124A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 2, 2012
Ordering Information
Package Interface Current Control, Inverting Marking1Part Number (Tape and Reel)2
SC70JW-10 S2Cwire 16-step AAT3104IJQ-1-T1
SC70JW-10 S2Cwire 32-step 4DXYY AAT3104IJQ-2-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
SC70JW-10
0.45 ± 0.10
0.05
±
0.05
2.10 ± 0.30
4°
± 4°
0.15 ± 0.05
2.00 ± 0.20
7°
± 3°
0.85 ± 0.15
1.10 MAX
0.100
0.225 ± 0.075
1.75 ± 0.10
2.20 ± 0.20
0.40 BSC
Top View
Side View End View
All dimensions in millimeters.
1. XYY = assembly and date code.
2. Sample stock is generally held on part numbers listed in BOLD.
15
AAT3104
DATA SHEET
Low Cost 1x/2x Four-Channel Charge Pump WLED Driver
Skyworks Solutions, Inc. • Phone [781] 376-3000 • Fax [781] 376-3100 • sales@skyworksinc.com • www.skyworksinc.com
202124A • Skyworks Proprietary Information • Products and Product Information are Subject to Change Without Notice. • July 2, 2012
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