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PDF AAT3167 Data sheet ( Hoja de datos )
| Número de pieza | AAT3167 | |
| Descripción | High Efficiency 1X/1.5X/2X Charge Pump | |
| Fabricantes | AAT | |
| Logotipo |  |
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AAT3167
High Efficiency 1X/1.5X/2X Charge
Pump for White LED Applications
General Description
Features
ChargePump™
The AAT3167 is a low noise, constant frequency
charge pump DC/DC converter that uses a tri-
• VIN Range: 2.7V to 5.5V
• Fully Programmable Current with Single Wire
mode load switch (1X), fractional (1.5X), and dou-
— 16-Step Logarithmic Scale
bling (2X) conversion to maximize efficiency for
— 14/18/27mA Max Current
white LED applications. The AAT3167 is capable of
— Four Low-Current Settings Down to 115µA
driving five LEDs for a total of 135mA from a 2.7V
to 5.5V input. The current sinks may be operated
— Low IQ (50µA) for Single-Channel, Low-
Current Mode
individually or in parallel for driving higher current
• Tri-Mode 1X, 1.5X, 2X Charge Pump for
LEDs. A low external parts count (two 1µF flying
capacitors and two small 1µF capacitors at IN and
Maximum Efficiency and VF Coverage
• Drives Up to Five LEDs
OUTCP) make this part ideally suited for small,
• Individual Main-Sub (4-1) Group Control
battery-powered applications.
• No Inductors, Low Noise Operation
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 115µA. For optimized efficiency, low-current set-
tings require only 50µA of housekeeping current.
• 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
• STDFN33-14 or QFN44-16 Package
Each output of the AAT3167 is equipped with built-
in protection for output short circuit and auto-dis-
able for load short-circuit conditions. Built-in soft-
www.DataSheet4U.com
start circuitry prevents excessive inrush current
during start-up. A low-current shutdown feature dis-
Applications
connects the load from the input and reduces qui-
escent current to less than 1µA.
• Color (RGB) Lighting
• Programmable Current Sink
The AAT3167 is available in a Pb-free, space-sav-
• Transmissive LCD Display
ing, thermally-enhanced, 14-pin 3x3mm STDFN or
• White LED Backlighting
16-pin 4x4mm QFN package and is rated over the
• White Photo Flash for Digital Still Cameras
-40°C to +85°C temperature range.
Typical Application
C1+
C1
1µF
C1-
C2+
C2-
2.7V to 5.5V
EN/SET
IN OUTCP
CIN
1µF
AAT3167
GND
D1
D2
EN/SET
D3
D4
D5
C2
1µF
D1 D2 D3 D4 D5
COUT
1µF
3167.2007.03.1.4
1
1 page  
AAT3167
High Efficiency 1X/1.5X/2X Charge
Pump for White LED Applications
Typical Characteristics
CIN = COUT = C1 = C2 = 1.0µF; TA = 25°C, VIN = 3.6V, unless otherwise noted.
Efficiency vs. Supply Voltage
100
5.1mA
90 VF = 3.0V
80
18mA
VF = 3.4V
70
60
50
40
30 350μA
20 VF = 2.7V
10
0
2.5 2.8 3.0 3.3 3.5 3.8 4.0 4.3 4.5 4.8 5.0 5.3 5.5
Supply Voltage (V)
EN
(2V/div)
OUT
(2V/div)
VSINK
(500mV/div)
IIN
(200mA/div)
Turn-On to 1X Mode
(VIN = 4.2V; 18mA Load)
Time (100µs/div)
EN
(2V/div)
OUT
(2V/div)
VSINK
(500mV/div)
IIN
(200mA/div)
Turn-On to 1.5X Mode
(VIN = 3.5V; 18mA Load)
Time (100µs/div)
EN
(2V/div)
OUT
(2V/div)
VSINK
(500mV/div)
IIN
(200mA/div)
Turn-On to 2X Mode
(VIN = 2.8V; 18mA Load)
Time (100µs/div)
EN
(2V/div)
VF
(1V/div)
IIN
(100mA/div)
Turn-Off from 1.5X Mode
(VIN = 3.5V; 18mA Load)
Time (100µs/div)
Current Matching vs. Temperature
19.0
18.8
18.6
18.4
18.2
18.0
17.8
17.6
17.4
17.2
17.0
-40
Channel 2 Channel 3
Channel 4
Channel 1
Channel 5
-20 0
20 40
60
Temperature (°C)
80
3167.2007.03.1.4
5
5 Page 
AAT3167
High Efficiency 1X/1.5X/2X Charge
Pump for White LED Applications
AS2Cwire Serial Interface Timing
EN/SET
Address
Address
THI
TLO
TLAT
12
17 18
0
Data
TLAT
1 2 . . . n <= 16
1
Data Reg 1
Data Reg 2
0n
0
Applications Information
LED Selection
Although the AAT3167 is designed for driving white
LEDs, the device also can be used to drive most
types of LEDs with forward voltage specifications
ranging from 2.0V to 4.7V. LED applications may
include main and sub-LCD display backlighting,
camera photo-flash applications, color (RGB)
LEDs, infrared diodes for remotes, and other loads
benefiting from a controlled output current generat-
ed from a varying input voltage. Since the D1 to D5
input current sinks 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 neces-
sary to drive high-VF type LEDs. The low-dropout
current sinks in the AAT3167 make it capable of
driving LEDs with forward voltages as high as 4.7V
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 AAT3167 operates at a fixed frequency of
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 AAT3167 soft-start feature prevents
noise transient effects associated with inrush cur-
rents during start-up of the charge pump circuit.
Capacitor Selection
Careful selection of the four external capacitors
(CIN, C1, C2, COUT) is important because they will
affect turn-on time, output ripple, and transient per-
formance. Optimum performance will be obtained
when low equivalent series resistance (ESR)
(<100mΩ) ceramic capacitors are used. A value of
1µF for all four capacitors is a good starting point
when choosing capacitors. If the LED current
sources are programmed only for light current lev-
els, then the capacitor size may be decreased.
3167.2007.03.1.4
11
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| PDF Descargar | [ Datasheet AAT3167.PDF ] | |
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