AAT1407 Advanced Analogic Technologies, Inc., AAT1407 Datasheet - Page 9

• Manufacturer Part Number: AAT1407
• Description: 6 Channel Led Backlight Driver With Integrated Boost And High Frequency Direct Pwm Dimming
• Manufacturer: Advanced Analogic Technologies, Inc.

Functional Block Diagram
Functional Description
The AAT1407 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.
The integrated boost (step-up) converter provides up to
45V output to drive multiple strings of series LEDs. The
maximum number of LEDs is dependent upon the for-
ward voltage of each LED. Six precision current sinks can
provide constant current drive for up to 66 white LEDs
depending upon LED V
single external resistor up to 30mA per string for a total
output current capability of 180mA. The controller
derives output feedback from the channel with the lowest
current sink voltage while maintaining the programmed
current in each LED string. This ensures the lowest pos-
sible output voltage, highest efficiency and continuous
operation with mismatched LED strings.
1407.2010.06.1.0
SwitchReg
TM
6 Channel LED Backlight Driver with Integrated Boost and High Frequency Direct PWM Dimming
F
. The LED current is set by a
COMP
SYNC
FSET
PWM
OVP
VCC
EN
V
REF
Osc
w w w . a n a l o g i c t e c h . c o m
Linear Reg
GND
Logic
IN
PGND
P
The AAT1407 is designed for maximum flexibility. The LED
strings may be disabled or used in parallel for increased
current capability. Thus, the AAT1407 allows operation
with fewer than 6 LED strings with the maximum number
of LEDs per channel set by the LED V
age of the boost converter. A lower number of LEDs can
also be used. Unused current sinks are disabled by tying
them to ground. The unique high voltage current sinks
support non-matching LED strings (LED quantity, type,
etc.). For high current applications, such as high-bright-
ness LEDs, multiple current sinks may be connected in
parallel providing up to 180mA per LED string.
The AAT1407 supports a high input PWM frequency to
help eliminate potential audio emissions caused by har-
monic/sub-harmonic resonance of the power stage. The
PWM dimming range is up to 1,000:1 (see Figure 1).
The output voltage is regulated by the string with the
highest voltage requirement, allowing a wide range of
LED characteristics. The boost switching frequency is
P
LX
SGND
S
S
RSET
PRODUCT DATASHEET
CS1
CS2
CS3
CS4
CS5
CS6
AAT1407
F
and the output volt-
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