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PDF AAT3156 Data sheet ( Hoja de datos )
| Número de pieza | AAT3156 | |
| Descripción | High Efficiency 1X/1.5X/2X Charge Pump For White LED Applications | |
| Fabricantes | Advanced Analogic Technologies | |
| Logotipo |  |
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AAT3156
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
General Description
Features
ChargePump™
The AAT3156 is a low noise, constant frequency
charge pump DC/DC converter that uses a tri-
mode load switch (1X), fractional (1.5X), and dou-
bling (2X) conversion to maximize efficiency for
white LED applications. The AAT3156 is capable of
driving six-channel LEDs at a total of 180mA from
a 2.7V to 5.5V input. The current sinks may be
operated individually or in parallel for driving high-
er-current LEDs. A low external parts count (two
1µF flying capacitors and two small 1µF capacitors
at VIN and VOUT) make this part ideally suited for
small battery-powered applications.
AnalogicTech's AS2Cwire™ (Advanced Simple
Serial Control™) serial digital input is used to
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.
• VIN Range: 2.7V to 5.5V
• Fully Programmable Current with Single Wire
— 16-Step Logarithmic Scale
— 15/20/30mA Max Current
— Four Low Current Settings Down to 50µA
— Low IQ (50µA) for Low Current Mode
• Tri-Mode 1X, 1.5X, and 2X Charge Pump for
Maximum Efficiency and VF Coverage
• Drives Six Channels of LEDs
• Individual Main/Sub-Group Control
• No Inductors, Low Noise Operation
• 1MHz Constant Switching Frequency
• Small Application Circuit
• Built-In Thermal Protection
• Built-In Auto-Disable For Open Circuit
• Automatic Soft-Start
• IQ <1µA in Shutdown
• Thermally-Enhanced QFN44-16 Package
Each output of the AAT3156 is equipped with built-
in protection for VOUT short circuit and auto disable
for LED failure condition. Built-in soft-start circuitry
www.DataSheet4U.comprevents excessive inrush current during start-up.
Applications
A low current shutdown feature disconnects the
• Color (RGB) Lighting
load from VIN and reduces quiescent current to less
than 1µA.
• Programmable Current Sinks
• White LED Backlighting
The AAT3156 is available in a space-saving, ther-
• White Photo Flash for DSCs
mally-enhanced 16-pin 4x4mm QFN package.
Typical Application
2.7V to 5.5V
VIN C1+
CIN C1-
1µF
C2+
AAT3156
C2-
VOUT
EN/SET
EN/SET
GND
D1
D2
D3
D4
D5
D6
C1
1µF
C2
1µF
D1 D2 D3 D4 D5 D6
COUT
1µF
3156.2005.06.1.1
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AAT3156
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
Typical Characteristics
Efficiency vs. Supply Voltage
100
90
80
70
60
50
2.8
4.1mA
VF = 2.9V
10.2mA
VF = 3.1V
20mA
VF = 3.4V
3.0 3.2 3.4 3.6 3.8 4.0 4.2
Supply Voltage (V)
EN
(2V/div)
CP
(2V/div)
VSINK
(500mV/div)
IIN
(200mA/div)
Turn-On to 1X Mode
(VIN = 4.2V; 20mA Load)
100µs/div
EN
(2V/div)
CP
(2V/div)
VSINK
(500mV/div)
IIN
(200mA/div)
Turn-On to 1.5X Mode
(VIN = 3.8V; 20mA Load)
Turn-On to 2X Mode
(VIN = 2.8V; 20mA Load)
EN
www.DataShee(2Vt/d4CivP) U.com
(2V/div)
VSINK
(500mV/div)
IIN
(200mA/div)
100µs/div
100µs/div
EN
(2V/div)
VF
(1V/div)
IIN
(100mA/div)
Turn-Off from 1.5X Mode
(VIN = 3.5V; 20mA Load)
100µs/div
Current Matching vs. Temperature
20.2
20.0
19.8
19.6
19.4
19.2
-40
Channel 2
Channel 1
Channel 5
Channel 3
Channel 4
Channel 6
-20 0 20 40 60 80
Temperature (°C)
3156.2005.06.1.1
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AAT3156
High Efficiency 1X/1.5X/2X Charge Pump
For White LED Applications
Max Current Register Settings—Address 4
Data
1
2
3
4
Max Current
20mA Max Scale
30mA Max Scale
15mA Max Scale
Low Current Mode1
Thermal Protection
The AAT3156 has a built-in thermal protection cir-
cuit 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.
Low Current Register Settings—Address 5
Applications Information
Data
D1-D4 (mA) D5-D6 (mA)
LED Selection
10
0
20
0
30
0
40
0
5 0 0.05
6 0 0.5
70
1
80
2
9 0.05
0
The AAT3156 is specifically intended for driving
white LEDs. However, the device design will allow
the AAT3156 to drive most types of LEDs with for-
ward voltage specifications ranging from 2.0V to
4.3V. LED applications may include main and sub-
LCD display backlighting, camera photo-flash appli-
cations, color (RGB) LEDs, infrared (IR) diodes for
remotes, and other loads benefiting from a con-
trolled output current generated from a varying input
voltage. Since the D1 to D6 constant current sinks
10 0.5
11 1
www.DataSheet4U.com12 2
0
0
0
are matched with negligible voltage dependence,
the LED brightness will be matched regardless of
the specific LED forward voltage (VF) levels.
13 0.05 0.05
14 0.5
0.5
15 1
1
16 2
2
In some instances (e.g., in high-luminous-output
applications such as photo-flash), it may be neces-
sary to drive high-VF type LEDs. The low-dropout
current sinks in the AAT3156 make it capable of
driving LEDs with forward voltages as high as 4.3V
Disabled Current Sinks
Current sink inputs that are not used should be dis-
abled. To disable and properly terminate unused
at full current from an input supply as low as 3.0V.
Current sinks can be paralleled to drive high-cur-
rent LEDs without complication.
current sink inputs, they must be tied to VOUT. If left
unconnected or terminated to ground, the part will
Device Switching Noise Performance
be forced to operate in 2X charge pump mode.
The AAT3156 operates at a fixed frequency of
Properly terminating unused current sink inputs is
important to prevent the charge pump modes from
prematurely activating. When properly terminated,
only a small sense current flows for each disabled
channel. The sense current for each disabled chan-
nel is less than 120µA.
The AAT3156 is also equipped with an "auto-disable"
feature to protect against an LED failure condition.
approximately 1MHz to control noise and limit har-
monics that can interfere with the RF operation of
cellular telephone handsets or other communica-
tion 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 solu-
tions. The AAT3156 soft-start feature prevents
noise transient effects associated with in-rush cur-
rents during start up of the charge pump circuit.
1. Low Current Mode requires the Max Current register to be set to Low Current Mode. Low Current Mode is unaffected by the settings
for Addresses 1-3.
3156.2005.06.1.1
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| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet AAT3156.PDF ] | |
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