SwitchRegTM 8 Channel LED Backlight Driver with Integrated Boost and High Frequency Direct PWM Dimming
The AAT1409 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. Eight precision cur-
rent sinks are programmed up to 45mA per string
through one external RSET resistor, supporting up to 881
white LEDs at 360mA 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 AAT1409 is available in the Pb-free, thermally
enhanced 24-pin 3x4 TQFN package.
• VIN Range: 4.5V to 5.5V / 5.0V to 26.0V
• LX Rated to 50V
• Maximum IOUT: 360mA
• Up to 92% Efficiency
• High Efficiency Light-Load Mode
• 8 LED Current Sinks up to 45mA/each
▪ ±2% Accuracy (21mA)
▪ ±2% Matching (21mA)
• Flexible Configurations
▪ Disable or Parallel
• Switching Frequency Options
▪ 675kHz or 1.3MHz
▪ Synchronize to System Clock
• PWM Direct Dimming Input
▪ Up to 100kHz Prevents Audio Interference
▪ Fast Turn-On/Off
▪ Wide 1,000:1 Dimming Range (100Hz)
• 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
• Notebook Computers
• Portable TV
• Portable DVD Players
• White LED Backlight
1. The maximum number of LEDs in each string is dependent upon the maximum VF of the diodes in that string. Under no event should the voltage at LX be exceeded.