Four-String, White LED Driver for LCD Backlight Applications

The ADD5211 is a four-string, white LED driver for backlight applications based on high efficiency, current mode, step-up converter technology. The boost controller drives an external MOSFET switch for step-up regulation from an input voltage of 4.5 V to 40 V and a pin adjustable operating frequency from 200 kHz to 1.2 MHz. An adjustable UVLO function is implemented to reduce input current during power-off.

The ADD5211 provides four regulated current sinks for uniform brightness intensity. Each current sink can be driven from 40 mA to 200 mA; the LED driving current is pin adjustable using an external resistor. With an input PWM interface, the ADD5211 drives up to four parallel strings of multiple series connected LEDs.

Additional features include LED short protection, LED open protection, boost output short protection, overvoltage protection, cycle-by-cycle current limit, and thermal shutdown for both the IC and the LED array. An open-drain fault output is also included. A programmable soft start is implemented to reduce inrush current during startup.

Applications

* LCD monitor and TV LED backlights

* Industrial lighting

* White LED driver based on an inductive boost controller

* Wide input voltage range: 4.5V to 40 V

* Adaptive output voltage to minimize power dissipation

* Adjustable operating frequency: 200 kHz to 1.2 MHz

* Programmable UVLO

* Programmable soft start time for boost converter

* Programmable external MOSFET switching rising/falling time

* Drives up to 4 LED current sinks with internal MOSFETs

* Brightness control with PWM input

* Adjustable LED current: 40 mA to 200 mA

* Headroom control to maximize efficiency

* LED dimming frequency: up to 25 kHz

* PWM dimming at 300 Hz: 1000:1

* Open-drain fault indicator

* LED open and LED short fault protection

* Thermal shutdown

* Undervoltage lockout (UVLO)

* 24-lead, 4 mm × 4 mm LFCSP