AAT1405 Advanced Analogic Technologies, Inc., AAT1405 Datasheet

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AAT1405

Manufacturer Part Number
AAT1405
Description
4 Channel Led Backlight Driver With Integrated Boost And High Frequency Direct Pwm Dimming
Manufacturer
Advanced Analogic Technologies, Inc.
Datasheet
General Description
The AAT1405 is a highly integrated, high efficiency LED
backlight solution for notebook computers, monitors and
portable TVs. The device operates from DC inputs, ciga-
rette lighter adapters, or multi-cell Li-ion batteries over
the 4.5V to 26V voltage range.
An integrated boost (step-up) converter provides up to
45V output for driving series LEDs. Four precision cur-
rent sinks are programmed up to 30mA per string
through one external R
white LEDs at 120mA total output current.
LED strings may be disabled or operated in parallel for
increased drive capability. The boost output voltage is
set by the LED string with the highest voltage require-
ment, allowing a wide range of LED characteristics.
The PWM dimming range at 100Hz is up to 1,000:1.
The boost switching frequency is selectable (up to
1.3MHz) to allow optimum efficiency and the smallest
external L/C filtering components. Alternatively, the
device may be synchronized to an external clock.
Boost current mode control provides fast response to
line and load transients. Integrated Light-Load mode
ensures highest efficiency across the entire load range.
Fault tolerant circuitry extends system life by disabling
open LED strings. The unique high voltage current sinks
prevent damage resulting from shorted LEDs.
The AAT1405 is available in the Pb-free, thermally
enhanced 24-pin 3x4 TQFN package.
1. The maximum number of LEDs in each string is dependent upon the maximum V
1405.2010.06.1.0
SwitchReg
TM
4 Channel LED Backlight Driver with Integrated Boost and High Frequency Direct PWM Dimming
SET
resistor, supporting up to 44
w w w . a n a l o g i c t e c h . c o m
1
F
of the diodes in that string. Under no event should the voltage at LX be exceeded.
Features
• V
• LX Rated to 50V
• Maximum I
• Up to 92% Efficiency
• High Efficiency Light-Load Mode
• 4 LED Current Sinks up to 30mA/each
• Flexible Configurations
• Switching Frequency Options
• PWM Direct Dimming Input
• Fault Tolerant: Open/Short LED(s)
• Current Limit Protection
• Over-Voltage Protection
• Over-Temperature Protection
• Soft-Start Minimizes Inrush Current
• TQFN34-24 Low Profile Package
• -40°C to +85°C Temperature Range
Applications
• Monitors
• Notebook Computers
• Portable TV
• Portable DVD Players
• White LED Backlight
IN
±2% Accuracy (21mA)
±2% Matching (21mA)
Disable or Parallel
675kHz or 1.3MHz
Synchronize to System Clock
Up to 100kHz Prevents Audio Interference
Fast Turn-On/Off
Wide 1,000:1 Dimming Range (100Hz)
Range: 4.5V to 5.5V / 5.0V to 26.0V
OUT
: 120mA
PRODUCT DATASHEET
AAT1405
1

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AAT1405 Summary of contents

Page 1

... TM 4 Channel LED Backlight Driver with Integrated Boost and High Frequency Direct PWM Dimming General Description The AAT1405 is a highly integrated, high efficiency LED backlight solution for notebook computers, monitors and portable TVs. The device operates from DC inputs, ciga- rette lighter adapters, or multi-cell Li-ion batteries over the 4 ...

Page 2

... TQFN34-24 0805 0603 PWM SYNC COMP RSET C3 R2 FSET R1 PGND WLED Backlight LX R3 OVP R4 CS1 CS2 CS3 CS4 GND SGND PRODUCT DATASHEET AAT1405 V : 45V at 120mA OUT C4 2.2μF 50V 0805 1405.2010.06.1.0 ...

Page 3

... Exposed paddle. Connect to PCB GND plane. PCB paddle should maintain acceptable junction temperature. TQFN34-24 (Top View SYNC FSET GND 2 18 GND OVP 3 17 GND EP COMP 4 16 PWM RSET 5 15 CS1 GND 6 14 CS2 GND PRODUCT DATASHEET AAT1405 3 ...

Page 4

... 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 20mW/°C above 25° PRODUCT DATASHEET AAT1405 Value Units -0.3 to 7.0 -0 0.3 CC ...

Page 5

... J(HYS The AAT1405 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. Output voltage must result in a voltage lower than the LX maximum rating under all operating conditions. ...

Page 6

... OUT 10 = 45V OUT 100 0 4.7 4.65 4.6 4.55 4.5 4.45 4.4 4.35 4 PRODUCT DATASHEET AAT1405 Boost Efficiency vs. Load Current (L = 10μ 4.7V; PWM = GND SET 28V IN OUT V = 12V OUT V = 24V OUT 60 80 ...

Page 7

... FSET = GND 1.12 FSET = Current Sink Matching vs. Temperature 1.6 1.4 1.2 1 0.8 0.6 0 PRODUCT DATASHEET AAT1405 Shutdown Current vs. Input Voltage ( Open) LX CSX Input Voltage ( 12V) IN -40 - Temperature (° 12V ...

Page 8

... I OUT (50mA/div (1A/div) Time (100μs/div 2.2μF; (AC coupled) (50mV/div) (AC coupled) (200mV/div) (1A/div) = 2.2μ PRODUCT DATASHEET AAT1405 Switching Waveforms (V = 12V 37V 2.2μF; OUT IN OUT L = 4.7μ 80mA) OUT OUT I LX Time (500ns/div) 1405 ...

Page 9

... PWM SYNC FSET Functional Description The AAT1405 is a highly integrated, high efficiency white LED backlight solution for notebook computers, monitors and portable TVs. The device operates from regulated DC inputs, cigarette lighter adapters, and multi-cell Li-ion batteries over a voltage range from 4.5V to 26V. ...

Page 10

... Figure 1: PWM Input Frequency vs. Dimming Range. 10 Fault Tolerant Operation The AAT1405 device is protected from faults arising from LED opens and/or shorts. An LED open condition will be detected by the controller at startup and during normal operation. The low voltage on the current sink is detected by the controller, which disables the feedback to the boost converter from that current sink ...

Page 11

... Channel LED Backlight Driver with Integrated Boost and High Frequency Direct PWM Dimming Application Information OVP Protection with Open LED Failure The AAT1405's OVP protection consists of a resistive divider network (R3 and R4) as shown in Figure 2. The resistor divider must be selected so that the voltage at ...

Page 12

... R2 (kΩ) Diode junction temperature can be estimated. 5.23 6.19 7.87 10.5 15.8 31 PRODUCT DATASHEET AAT1405 ) and package thermal resis should be considered for high pulsed FSM rating drops with increasing con- FSM AVG OUT ...

Page 13

... IN(MIN) Compensation Component Selection · The AAT1405 Boost architecture uses peak current mode control to eliminate the double pole effect of the output L&C filter and simplifies the compensation loop design. The current mode control architecture simplifies the transfer function of the control loop one-pole, one left plane zero and one right half plane (RHP) system in frequency domain ...

Page 14

... L · I · OUT L1 VIN Figure 3: AAT1405 Equivalent Output Stage recommended to design the bandwidth to one decade lower than the frequency of RHP zero to guaran- tee the loop stability. A series capacitor and resistor network (R1 and C3) connected to the COMP pin sets the 4 ...

Page 15

... C1 Taiyo Yuden, GMK325BJ106KN-T, 10μF, 35V, X5R,1210; OR Murata GRM32ER71H106K, 10μF, 50V, X7R, 1210 C2 2.2μF, 10V, 0603 C3 15nF, 10V, 0603 C4 Murata, GRM31CR71H225KA88L, 2.2μF, 50V, X7R, 1206 R1, R2, R3, R4 Carbon Film resistors, 1%, 0603 Figure 4: AAT1405IMK Evaluation Board Schematic. Figure 5: AAT1405IMK Evaluation Board Top Side Layout. 1405.2010.06.1 4.7μ ...

Page 16

... Marking 1 K3XYY TQFN34-24 3 1.700 ± 0.050 R(5x) Detail “A” Bottom View 0.203 REF PRODUCT DATASHEET AAT1405 Part Number (Tape and Reel) 2 AAT1405IMK-T1 0.210 ± 0.040 0.400 BSC Detail “A” 1405.2010.06.1.0 ...

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