AAT3150IWP-T1 [SKYWORKS]
LED Driver;
| 型号： | AAT3150IWP-T1 |
| 厂家： | 
SKYWORKS SOLUTIONS INC. |
| 描述： | LED Driver 驱动 光电二极管 接口集成电路 |
| 文件： | 总15页 (文件大小：1088K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
DATA SHEET
AAT3150
High Efficiency 1X/1.5X Charge Pump For White LED Applications
General Description
Features
The AAT3150 is a low noise, constant frequency charge
pump DC/DC converter that uses a dual mode load
switch (1X) and fractional (1.5X) charge pump conver-
sion to maximize efficiency for white LED applications.
The AAT3150 is capable of driving four white LEDs at a
total of 120mA from a 2.7V to 5.5V input. The current
sinks may be operated individually or in parallel for driv-
ing higher-current LEDs. A low external parts count (two
1µF flying capacitors and two small 1µF capacitors at VIN
and VOUT) makes the AAT3150 ideally suited for small
battery-powered applications.
•ꢀ VIN Range: 2.7V to 5.5V
•ꢀ FullyꢀProgrammableꢀCurrentꢀwithꢀSingleꢀWire
16-Step Logarithmic Scale
15/20/30mA Max Current
Four Low-Current Settings Down to 50µA
Low IQ (50µA) for Low-Current Mode
▪
▪
▪
▪
Individual Channel ON/OFF Control
▪
•ꢀ Dualꢀ Modeꢀ 1Xꢀ andꢀ 1.5Xꢀ Chargeꢀ Pumpꢀ forꢀ Maximumꢀ
Efficiency and VF Coverage
•ꢀ DrivesꢀFourꢀChannelsꢀofꢀLEDs
•ꢀ NoꢀInductors,ꢀLowꢀNoiseꢀOperation
•ꢀ 1MHzꢀConstantꢀSwitchingꢀFrequency
•ꢀ SmallꢀApplicationꢀCircuit
•ꢀ Built-InꢀThermalꢀProtection
•ꢀ Built-InꢀAuto-DisableꢀforꢀShort-Circuit
•ꢀ AutomaticꢀSoftꢀStart
Skyworks AS2Cwire™ (Advanced Simple Serial Control)
serial digital input is used to individually enable, disable,
and set current for each LED with a 16-level logarithmic
scale plus four low-current settings down to 50µA for
optimized efficiency, with a low housekeeping current of
only 50µA.
•ꢀ IQ <1µA in Shutdown
•ꢀ TDFN33-12ꢀPackage
The charge pump output of the AAT3150 is equipped
with built-in protection for VOUT. Each current sink input
has short-circuit and auto-disable to guard against LED
failure 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.
Applications
•ꢀ Colorꢀ(RGB)ꢀLighting
•ꢀ ProgrammableꢀCurrentꢀSinks
•ꢀ WhiteꢀLEDꢀBacklighting
•ꢀ WhiteꢀPhotoꢀFlashꢀforꢀDigitalꢀStillꢀCameras
The AAT3150 is available in a Pb-free, space-saving,
thermally-enhanced, 12-pin 3x3mm TDFN package.
Typical Application
VIN
2.7V to 5.5V
C1+
C1
1µF
C
IN
C1-
1µF
C2+
C2
1µF
AAT3150
C2-
VOUT
COUT
1µF
D1
D2
D3
D4
EN/SET
D1
D2
D3
D4
EN/SET
GND
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DATA SHEET
AAT3150
High Efficiency 1X/1.5X Charge Pump For White LED Applications
Pin Descriptions
Pin #
Symbol
Function
1
2
3
4
D4
EN/SET
C1+
Current sink input #4.
AS2Cwire serial interface control pin.
Flying capacitor 1 positive terminal. Connect a 1µF ceramic capacitor between C1+ and C1-.
Flying capacitor 1 negative terminal.
C1-
Charge pump output to drive load circuit. Requires a 1µF or larger ceramic capacitor connected between
this pin and ground.
5
VOUT
6
7
8
C2+
C2-
VIN
GND
D1
Flying capacitor 2 positive terminal. Connect a 1µF ceramic capacitor between C2+ and C2-.
Flying capacitor 2 negative terminal.
Input power supply. Requires a 1µF or larger ceramic capacitor connected between this pin and ground.
Ground.
Current sink input #1.
Current sink input #2.
Current sink input #3.
Exposedꢀpaddleꢀ(bottom).ꢀConnectꢀtoꢀGNDꢀdirectlyꢀbeneathꢀpackage.
9
10
11
12
EP
D2
D3
Pin Configuration
TDFN33-12
(Top View)
1
2
3
4
5
6
12
11
10
9
D4
EN/SET
C1+
D3
D2
D1
GND
C1-
8
VOUT
C2+
VIN
C2-
7
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DATA SHEET
AAT3150
High Efficiency 1X/1.5X Charge Pump For White LED Applications
Absolute Maximum Ratings1
Symbol
Description
Value
Units
VIN
Input Voltage
EN/SETꢀtoꢀGNDꢀVoltage
Maximum DC Output Current
Junction Temperature Range
Maximum Soldering Temperature (at Leads)
Operating Temperature Range
-0.3 to 6
-0.3 to VIN + 0.3
150
V
V
mA
°C
°C
°C
VEN/SET
2
IOUT
TJ
TLEAD
TA
-40 to 150
300
-40 to 85
Thermal Information3
Symbol
Description
Maximum Power Dissipation4
Maximum Thermal Resistance
Value
Units
PD
qJA
2.0
50
W
°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. Based on long-term current density limitation.
3. Mounted on an FR4 board.
4.ꢀDerateꢀ20mW/°Cꢀaboveꢀ25°C.
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DATA SHEET
AAT3150
High Efficiency 1X/1.5X 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
Conditions
Min Typ Max Units
VIN
Operation Range
2.7
27
5.5
1
3
V
1XꢀMode,ꢀ3.0ꢀ≥ꢀVINꢀ≥ꢀ5.5,ꢀActive,ꢀNoꢀLoadꢀCurrent
1.5XꢀMode,ꢀ3.0ꢀ≥ꢀVINꢀ≥ꢀ5.5,ꢀActive,ꢀNoꢀLoadꢀCurrent
50µA Setting, 1X Mode
EN/SET = 0
ISET = 30mA, TA = 25°C
0.3
1
50
mA
ICC
Operating Current
µA
µA
mA
ISHDN
IDX
Shutdown Current
ISINK Current Accuracy2
1
33
30
Current Matching Between Any
Two Current Sink Inputs3, 4
1X to 1.5X Transition Threshold
at Any ISINK Pin
I(D-Match)
VTH
VF:D1:D4 = 3.6V
ISET = 20mA
0.5
%
150
mV
Charge Pump Section
TSS
FCLK
Soft-Start Time
Clock Frequency
100
1000
µs
kHz
EN/SET
VIL
VIH
TEN/SET LO
Enable Threshold Low
EnableꢀThresholdꢀHigh
EN/SET Low Time
VIN = 2.7V
VIN = 5.5V
0.4
75
V
V
1.4
0.3
µs
ns
µs
µs
µs
µA
TEN/SET_HI_MIN MinimumꢀEN/SETꢀHighꢀTime
TEN/SET_HI_MAX MaximumꢀEN/SETꢀHighꢀTime
50
75
500
500
1
TOFF
TLAT
IEN/SET
EN/SET Off Timeout5
EN/SET Latch Timeout6
EN/SET Input Leakage
-1
1. The AAT3150 is guaranteed to meet performance specifications over the -40°C to +85°C operating temperature range and is assured by design, characterization, and correla-
tion with statistical process controls.
2. Determined by the average of all active channels.
3. Current matching is defined as the deviation of any sink current at IOUT = 20mA and 2mA.
4. Specification applies only to the tri-mode charge pump.
5. The EN/SET pin must remain logic low (less than VIL) for the duration of longer than 500µs to guarantee the off timeout.
6. The EN/SET pin must remain logic high (greater than VIH) for the duration of longer than 500µs to guarantee the latch timeout.
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DATA SHEET
AAT3150
High Efficiency 1X/1.5X Charge Pump For White LED Applications
Typical Characteristics
3150 Backlight Efficiency vs. Supply Voltage
Turn-On to 1X Mode
(V = 4.2V; 20mA Load)
IN
100
90
20mA
EN
80
70
60
50
(2V/div)
CP
(2V/div)
V
SINK
1mA
(500mV/div)
10.2mA
40
I
IN
30
(200mA/div)
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
Supply Voltage (V)
Time (100µs/div)
Turn-On to 1.5X Mode
Turn-Off from 1.5X Mode
(V = 3.5V; 20mA Load)
IN
(V = 3.5V; 20mA Load)
IN
EN
EN
(2V/div)
(2V/div)
CP
V
F
(2V/div)
(1V/div)
V
SINK
(500mV/div)
I
IN
I
IN
(100mA/div)
(200mA/div)
Time (100µs/div)
Time (500µs/div)
Current Matching vs. Temperature
20.4
20.2
20.0
19.8
19.6
19.4
19.2
19.0
Channel 2
Channel 4
Channel 3
Channel 1
-40
-20
0
20
40
60
80
Temperature (°C)
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DATA SHEET
AAT3150
High Efficiency 1X/1.5X Charge Pump For White LED Applications
Typical Characteristics
Load Characteristics
Load Characteristics
(V = 3.7V; 1.5X Mode; 15mA Load)
IN
(V = 3.9V; 1.5X Mode; 20mA Load)
IN
V
V
IN
IN
(40mV/div)
(40mV/div)
CP
CP
(40mV/div)
(40mV/div)
V
V
SINK
SINK
(40mV/div)
(40mV/div)
Time (500ns/div)
Time (500ns/div)
Load Characteristics
EN/SET Latch Timeout vs. Input Voltage
(V = 4.2V; 1.5X Mode; 30mA Load)
IN
350
300
250
200
150
100
50
V
IN
(40mV/div)
-40°C
CP
(40mV/div)
25°C
85°C
V
SINK
(40mV/div)
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
Time (500ns/div)
Input Voltage (V)
Input Ripple vs. Input Voltage
EN/SET Off Timeout vs. Input Voltage
20
18
16
14
12
10
8
400
350
300
250
200
150
100
50
30mA
-40°C
20mA
6
25°C
85°C
10.2mA
4
2
0
0
2.50 2.75 3.00 3.25 3.50 3.75 4.00 4.25 4.50 4.75 5.00
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
Input Voltage (V)
Input Voltage (V)
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DATA SHEET
AAT3150
High Efficiency 1X/1.5X Charge Pump For White LED Applications
Typical Characteristics
Enable Threshold High vs. Input Voltage
Enable Threshold Low vs. Input Voltage
1.2
1.1
1
1.2
1.1
1
-40°C
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
-40°C
25°C
85°C
25°C
85°C
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
Input Voltage (V)
Input Voltage (V)
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DATA SHEET
AAT3150
High Efficiency 1X/1.5X Charge Pump For White LED Applications
Functional Block Diagram
C1+ C1- C2+ C2-
1X and 1.5X
Charge Pump
VIN
VOUT
Soft-Start
Control
1MHz
Oscillator
Voltage
Reference
D/A
D1
D2
D3
D4
D/A
D/A
D/A
6 x 16 bit
ROM
AS2Cwire
Interface
EN/SET
GND
stant current sinks, the voltage observed on any single
given input will be determined by the difference between
VOUT and the actual forward voltage (VF) of the LED being
driven.
Functional Description
The AAT3150 is a dual mode load switch (1X) and high
efficiency (1.5X) charge pump device intended for white
LED backlight applications. To maximize power conver-
sion 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 volt-
age. As the battery discharges over time, the AAT3150
charge pump is enabled when any of the four current
sinks near dropout.
Since the constant current levels for the AAT3150 are
programmable,ꢀ noꢀ PWMꢀ (pulseꢀ widthꢀ modulation)ꢀ orꢀ
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.”
Withꢀitsꢀhigh-speedꢀserialꢀinterfaceꢀ(>1MHzꢀdataꢀrate),ꢀ
the LED current drive can be changed successively to
brighten or dim LEDs in smooth transitions (e.g., to fade
out) or in abrupt steps, giving the user complete pro-
grammability and real-time control of LED brightness.
The AAT3150 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 1µF ceramic charge pump output capaci-
tor (COUT).
For each Max Current scale, there are 16 current level
settings separated from one another by approximately
1dB. Code 1 is full-scale current and Code 15 is full-scale
current attenuated by roughly 14dB. Code 16 is reserved
as a “no current” setting (see Table 1).
The AAT3150 constant current sinks can drive four indi-
vidual LEDs with a maximum current of 30mA per chan-
nel. The AS2Cwire serial interface enables the AAT3150
and sets the constant current sink magnitudes.
The AAT3150 has an additional Low Current mode with
reduced quiescent current. This mode is especially useful
for low-current applications where a continuous, low-
current state is maintained. The reduction in quiescent
current significantly lowers the impact due to maintain-
ing a continuous backlighting state. In addition, the user
has the ability to turn on or turn off individual channels
via the AS2Cwire interface.
Constant Current Output Level Settings
The constant current level for the LED channels is set via
the AS2Cwire serial interface according to a logarithmic
scale. In this manner, LED brightness appears to change
linearly when the settings in the scale are traversed.
Because the inputs D1 to D4 are true independent con-
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DATA SHEET
AAT3150
High Efficiency 1X/1.5X Charge Pump For White LED Applications
held high for time TLAT. Address or data is differentiated
by the number of EN/SET rising edges. Since the data
20mA Max1
IOUT (mA)
30mA Max 15mA Max
Data
IOUT (mA)
IOUT (mA)
registers are 4 bits each, the differentiating number of
pulses is 24 or 16, so that Address 1 is signified by 17
rising edges, Address 2 by 18 rising edges, and so forth.
Data is set to any number of rising edges between 1 and
including 16. A typical write protocol is a burst of EN/SET
rising edges, signifying a particular address, followed by
a pause with EN/SET held high for the TLAT timeout
period, a burst of rising edges signifying data, and a TLAT
timeout for the data registers. Once an address is set,
then multiple writes to the corresponding data register
are allowed.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
20.0
17.8
15.9
14.3
12.7
11.1
10.2
8.9
7.9
7.0
6.3
5.7
30.0
26.7
23.8
21.4
19.0
16.7
15.2
13.3
11.9
10.5
9.5
15.0
13.3
11.9
10.7
9.5
8.3
7.6
6.7
6.0
5.2
4.8
4.3
3.8
3.3
3.1
0.0
8.6
7.6
6.7
6.2
WhenꢀEN/SETꢀisꢀheldꢀlowꢀforꢀanꢀamountꢀofꢀtimeꢀgreaterꢀ
than TOFF, the AAT3150 enters shutdown mode and
draws less than 1µA from the supply. Address 1 is the
default address on the first rising edge after the AAT3150
hasꢀbeenꢀdisabled.ꢀWheneverꢀshutdownꢀmodeꢀisꢀentered,ꢀ
all registers are reset to 1.
5.1
4.4
4.1
0.0
0.0
Table 1: Constant Current Programming
Levels (mA)2.
AS2Cwire Addressing
AS2Cwire Serial Interface
A number of addresses are available to control all of the
part’s functionality. Use Address 1 to program all four
LED channels to any one of 16 possible settings that
depend on the Max Current scale setting. Use Address 4
to program the Max Current register, which sets the Max
Current scale. Address 5 programs the Low Current reg-
ister. The Low Current register controls the highly effi-
cient Low Current mode.
The AS2Cwire single wire interface is used to set the pos-
sible combinations of current levels and LED channel
states.
AS2Cwire relies on the number of rising edges of the EN/
SET pin to address and load the registers. AS2Cwire
latches data or address after the EN/SET pin has been
AS2Cwire Serial Interface Timing
Address
Data
THI
TLAT
TLO
TLAT
EN/SET
1
2
17
1
18
1
2 . . .
n <= 16
2
Address
1
n
Data Reg 1
1. The device defaults to the 20mA Max scale. Use the Max Current Register to change the Max Scale.
2. There is an additional Low Current mode with currents down to 50µA. See the Low Current Register Settings section.
Skyworks Solutions, Inc.
•
Phone [781] 376-3000
•
Fax [781] 376-3100
•
sales@skyworksinc.com
•
www.skyworksinc.com
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DATA SHEET
AAT3150
High Efficiency 1X/1.5X Charge Pump For White LED Applications
WhenꢀtheꢀMaxꢀCurrentꢀregisterꢀisꢀprogrammedꢀtoꢀ1,ꢀ4,ꢀ
the Low Current register with 1-16 rising edges. The part
will update to the new Low Current mode setting and
operate with significantly reduced quiescent current.
or 5, changing the data for Address 1 will result in the
corresponding values found in the Constant Current
Programmingꢀ Levelsꢀ tableꢀ (Tableꢀ 1).ꢀ Whenꢀ theꢀ Maxꢀ
Current register is programmed to 4, the part is pro-
grammed to operate in Low Current mode and the Data
for Address 1 is irrelevant. In Low Current mode, the
Low Current register takes precedence. See Table 4 for
the available current level settings.
Data
Max Current
1
2
3
4
20mA Max Scale
30mA Max Scale
15mA Max Scale
Low Current Mode
Table 3: Max Current Register Settings—
Address 4.
Address EN/SET Edges
Addressed Register
1
4
5
6
17
20
21
22
D1-D4 Current
Max Current
Low Current
Data
D1-D4 (mA)
ON/OFF Control
1
2
3
4
0.05
0.5
1
Table 2: Addresses for Setting Current Level.
2
Max Current and Low Current Registers
Table 4: Low Current Register Settings—
Address 5.
Use the Max Current and Low Current registers to pro-
gram constant current settings outside of the 20mA Max
scale. By default (without changing the Max Current reg-
ister), the AAT3150 operates in the 20mA Max scale (see
Constant Current Programming Levels). For example, to
change to the 30mA Max scale, address the Max Current
register with 20 rising edges and pause for TLAT. Program
the Max Current register with 2 rising edges and pause
for TLAT. The part will next operate in the same Data row,
but for the setting found in the 30mA Max column. Next,
to change to a different setting on the 30mA Max scale,
address the D1-D4 register with 17 rising edges. Program
the new constant current level with 1-16 rising edges.
The part will update to the new Data setting according to
the Constant Current Programming Levels table.
Individual ON/OFF Control
LED sinks D1, D2, D3, and D4 can be turned on or off
individually by writing data to Address 6. By default (no
programming), all channels are set to DATA 1 or ON. To
turn off a channel (or channels) the D1-D4 ON/OFF regis-
ter should be addressed with 22 rising edges and a pause
for TLAT. Next, to turn off (e.g.) D1, address the register
with 2 rising edges followed by a pause for TLAT. D1 will
now turn off. The ON/OFF settings are shown in Table 5.
Disabled Current Sinks
Current sink inputs that are not used should be disabled.
To disable and properly terminate unused current sink
The AAT3150 has a distinct Low Current mode with ultra-
low quiescent current. For driving currents of 2mA or
less, the part operates with significantly reduced quies-
cent current. This is particularly useful for applications
requiring an “always on” condition, such as transmissive
displays. As an example, to change to Low Current mode,
address the Max Current register with 20 rising edges
and pause for TLAT. Program the Max Current register with
4 rising edges and pause for TLAT. Address the Low Current
register with 21 rising edges and pause for TLAT. Program
inputs, they must be tied to VOUT
.
Properly terminating unused current sink inputs is
important to prevent the charge pump modes from pre-
maturelyꢀ activating.ꢀ Whenꢀ properlyꢀ terminated,ꢀ onlyꢀ aꢀ
small sense current flows for each disabled channel. The
sense current for each disabled channel is 120µA.
The AAT3150 is also equipped with an “auto-disable”
feature to protect against an LED failure condition.
Skyworks Solutions, Inc.
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DATA SHEET
AAT3150
High Efficiency 1X/1.5X Charge Pump For White LED Applications
In some instances (e.g., in high luminous output appli-
Code
D4
D3
D2
D1
cations such as photo flash), it may be necessary to
drive high-VF type LEDs. The low dropout current sinks
in the AAT3150 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. Current sinks can be paral-
leled to drive high-current LEDs without complication.
1*
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
ON
ON
ON
ON
ON
ON
ON
ON
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
ON
ON
ON
ON
ON
OFF
OFF
ON
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
ON
OFF
OFF
OFF
OFF
ON
ON
OFF
OFF
ON
Device Switching Noise Performance
The AAT3150 operates at a fixed frequency of approxi-
matelyꢀ1MHzꢀtoꢀcontrolꢀnoiseꢀandꢀlimitꢀharmonicsꢀthatꢀ
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 induc-
tor-based DC/DC boost converter white LED backlight
solutions. The AAT3150 soft-start feature prevents noise
transient effects associated with inrush currents during
start-up of the charge pump circuit.
ON
ON
ON
OFF
OFF
OFF
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
OFF
OFF
ON
ON
OFF
OFF
Table 5: ON/OFF Register Settings—
Address 6.
Thermal Protection
Power Efficiency and Device Evaluation
The AAT3150 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 VOUT pin.
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 architec-
ture and design of the AAT3150, it is very difficult to
measure efficiency in terms of a percent value compar-
ing input power over output power.
Applications Information
Since the AAT3150 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 D4)
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.
LED Selection
The AAT3150 is specifically intended for driving white
LEDs.ꢀHowever,ꢀtheꢀdeviceꢀdesignꢀwillꢀallowꢀtheꢀAAT3150ꢀ
to drive most types of LEDs with forward voltage speci-
fications ranging from 2.0V to 4.3V. LED applications
may include main and sub-LCD display backlighting,
cameraꢀ photo-flashꢀ applications,ꢀ colorꢀ (RGB)ꢀ LEDs,ꢀ
infrared (IR) diodes for remotes, and other loads bene-
fiting from a regulated output current generated from a
varying input voltage. Since the D1 to D4 constant cur-
rent sinks are matched with negligible voltage depen-
dence, the LED brightness will be matched regardless of
the specific LED forward voltage (VF) levels.
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.
*Indicates default code.
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DATA SHEET
AAT3150
High Efficiency 1X/1.5X Charge Pump For White LED Applications
The AAT3150 efficiency may be quantified under very
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:
specific conditions and is dependent upon the input volt-
age versus the output voltage seen across the loads
applied to inputs D1 through D4 for a given constant
current setting. Depending on the combination of VIN and
voltages sensed at the current sinks, the device will
operateꢀinꢀloadꢀswitchꢀmode.ꢀWhenꢀanyꢀoneꢀofꢀtheꢀvolt-
ages sensed at the current sinks nears dropout, the
device will operate in 1.5X charge pump mode. Each of
these modes will yield different efficiency values. Refer
to the following two sections for explanations for each
operational mode.
POUT
PIN
VOUT · IOUT
VOUT
η =
=
=
VIN · 1.5IOUT
1.5VIN
-or-
VOUT
η(%) = 100
1.5V
IN
Load Switch Mode Efficiency
Capacitor Selection
The AAT3150 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.ꢀWhenꢀinꢀloadꢀswitchꢀmode,ꢀtheꢀvoltageꢀconversionꢀ
efficiency is defined as output power divided by input
power:
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 gener-
al, 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 constant current sinks
are only programmed for light current levels, then the
capacitor size may be decreased.
POUT
η =
PIN
The expression to define the ideal efficiency (h) can be
rewritten as:
Capacitor Characteristics
POUT VOUT · IOUT VOUT
=
η =
=
Ceramic composition capacitors are highly recommend-
ed over all other types of capacitors for use with the
AAT3150. Ceramic capacitors offer many advantages
over their tantalum and aluminum electrolytic counter-
parts. A ceramic capacitor has very low ESR, is lowest
cost, has a smaller PCB footprint, and is non-polarized.
Low ESR ceramic capacitors help maximize charge pump
transient response. Since ceramic capacitors are non-
polarized, they are not prone to incorrect connection
damage.
PIN
VIN · IOUT
VIN
-or-
V
OUT
η(%) = 100
VIN
Charge Pump Section Efficiency
The AAT3150 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 (h) 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 (h) for an ideal 1.5X charge pump can typi-
cally be expressed as the output power divided by the
input power.
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.
POUT
η =
PIN
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DATA SHEET
AAT3150
High Efficiency 1X/1.5X Charge Pump For White LED Applications
itors greater than 1µF are not typically required for
Ceramic Capacitor Materials
AAT3150 applications.
Ceramic capacitors less than 0.1µF are typically made
fromꢀNPOꢀorꢀC0Gꢀmaterials.ꢀNPOꢀandꢀC0Gꢀmaterialsꢀgen-
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., greater than 2.2µF) are often
available in low-cost Y5V and Z5U dielectrics, but capac-
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.
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DATA SHEET
AAT3150
High Efficiency 1X/1.5X Charge Pump For White LED Applications
Ordering Information
Package
Marking1
Part Number (Tape and Reel)2
AAT3150IWP-T1
TDFN33-12
NSXYY
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 Information3
TDFN33-12
Index Area
Detail "A"
0.43 0.05
0.1 REF
C0.3
Pin 1 Indicator
(optional)
3.00 0.05
1.70 0.05
Top View
Bottom View
Detail "A"
0.05 0.05
Side View
All dimensions in millimeters.
1. XYY = assembly and date code.
2. Sample stock is generally held on part numbers listed in BOLD.
3. The leadless package family, which includes QFN, TQFN, DFN, TDFN and STDFN, has exposed copper (unplated) at the end of the lead terminals due to the manufacturing
process. A solder fillet at the exposed copper edge cannot be guaranteed and is not required to ensure a proper bottom solder connection.
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DATA SHEET
AAT3150
High Efficiency 1X/1.5X Charge Pump For White LED Applications
Copyright © 2012 Skyworks Solutions, Inc. All Rights Reserved.
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works may change its documentation, products, services, specifications or product descriptions at any time, without notice. Skyworks makes no commitment to update the materials or information and shall have no
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Customers are responsible for their products and applications using Skyworks products, which may deviate from published specifications as a result of design defects, errors, or operation of products outside of pub-
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Skyworks Solutions, Inc.
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