Fade-in/Fade-Out, 4-Channel Backlight Driver employs 2 LDOs.

Press Release Summary:



Able to drive 4 white LEDs at 124 mA total from 2.7-5.5 V input, AAT2869 constant-frequency (0.9 MHz) charge pump DC/DC converter uses dual-mode load switch (1x) and fractional (1.5x) conversion to maximize efficiency. External parts consist of two 1 µF flying capacitors and two 1 µF capacitors at IN and OUTCP. Along with fade-in/fade-out feature for backlight turn-on/-off, IC integrates two 150 mA LDO linear regulators, AS2Cwire(TM) serial digital input, and short-circuit protection.



Original Press Release:



AAT 2869 Fade-In/Fade-Out 4 Channel Backlight Driver with Dual LDOs



Lighting Management Units

The AAT2869 is a low-noise, constant-frequency charge pump DC/DC converter that uses a dual-mode load switch (1x) and fractional (1.5x) conversion to maximize efficiency for white LED applications. The AAT2869 is capable of driving 4 white LEDs at a total of 124mA from a 2.7V to 5.5V input. The current sinks may be operated individually or in parallel for driving higher-current LEDs. A low external parts count (two 1ìF flying capacitors and two small 1ìF capacitors at IN and OUTCP) makes the AAT2869 ideally suited for small battery-powered applications. The fade-in/fade-out feature makes backlight turn-on/turn-off more visual comfortable. The AAT2869 also includes two 150mA low, drop-out linear regulators as additional power supplies for display and related camera power. The LDO voltage is also programmable.

AnalogicTech's Advanced Simple Serial Control(TM) (AS2Cwire(TM)) serial digital input is used to enable, disable and set the maximum LED current to one of 32 levels for the LEDs, to enable/disable the LDOs, and to set the LDO's output. The programmable LED current ranges from 31mA to 0.4mA.

Each output of the AAT2869 is equipped with built-in protection for short-circuit and auto-disable for load short-circuit conditions. The soft-start circuitry prevents excessive inrush current at charge pump start-up and mode transitions. The AAT2869 is available in the Pb-free, space-saving TQFN3.0x2.2-18L package, and operates over the -40°C to 85°C ambient temperature range.

Features
2.7V to 5.5V Supply Voltage Range
Charge Pump for LED Driver
Dual Mode 1x/1.5x
Drives up to 4 LEDs with up to 31mA each
Linear LED Output Control Options
Maximum LED Current Set by AS²Cwire(TM) Interface, 32 Steps
Fade In and Fade Out
0.9MHz Constant Frequency
Automatic Soft-Start Limits Inrush Current
Dual 150mA LDOs
Five Voltages with 1.2V, 1.5V, 1.8V, 2.8V, and 3.0V, Sixteen Combinations Set by AS²Cwire(TM)
Enable Control Independently by AS²Cwire(TM)
Integrated Discharge Resistor when Disabled
< 1.0µA in Shutdown
Short Circuit Protection
Small Application Circuit
-40°C to 85°C Temperature Range
RoHS Compliant, Halogen-Free TQFN3.0x2.2-18 Package

Applications
  • Camera Phones
  • Digital Cameras
  • Media Players
  • PDAs and Handheld Computers
  • Smart Phones
  • All Topics