Adjustable TFT Bias Supply with WLED Driver

The LTC3524 is an integrated BIAS and white LED power converter solution for small/medium-sized polysilicon thin film transistor (TFT) liquid crystal (LCD) display panels. The device operates from a single Lithium-Ion/polymer battery or any voltage source between 2.5V and 6V.

A 1.5MHz synchronous boost converter generates a programmable low noise, high efficiency 25mA TFT supply of up to 6.0V. Regulated, low ripple charge pumps are used to generate up to +20V and –20V at 2mA. Output sequencing is internally controlled to insure proper initialization and rapid discharge of the LCD panel in shutdown.

A second 1.5MHz boost converter powers one or two LED strings with up to five series elements each. LED current and display brightness can be controlled over a wide range using analog or digital means up to 25mA.

The LTC3524 is offered in the 4mm × 4mm 24-pin QFN package, minimizing the total solution footprint.

Applications

* PDAs, Palmtop Computers

* Digital Still and Video Cameras

* Handheld GPS

* Portable Instrument Displays

* Portable Media Players

* Generates Three Adjustable, Low Noise Rails for Small/Medium TFT Displays

* Drives Up to Ten White LEDs

* LED Dimming and Open-Circuit Protection

* Controlled Power-Up/Power-Down Sequencing

* 1.5MHz Fixed Frequency, Low Noise Operation

* VIN Range 2.5V to 6V, VOUT Range 3V to 6V

* TFT Supply Efficiency Up to 90%

* LED Supply Efficiency Up to 78%

* Two independently Enabled LED Strings

* 200 to 1 True Color PWM™ Dimming

* Tiny External Solution

* 24-Lead QFN Package (4mm × 4mm × 0.75mm)