Reduce the Cost and Complexity of Medium LCD LED
Backlights with a Single Inductor LED Driver for 60 LEDs
Design Note 462
Daniel Chen
Introduction
One inductor, one IC, one string of LEDs. This is the
conventional way to build a boost LED driver for LCD
display backlights. Although this is a perfectly acceptable solution for small LCD displays that only require a
few strings, in larger displays the number of control ICs
and inductors multiplies quickly, as do the expenses and
PCB real estate requirements. This is a major hurdle in
the race to replace CCFLs with robust, spectrally superior
LEDs in medium sized, bright displays.
A better driver is needed to bring the cost and complexity of LED backlights in line with CCFLs. The LT3598
answers the call by driving six strings of ten LEDs at up
to 30mA per string. It also has a built-in power switch
to save space and design time. Efficiency is optimized
via an adaptive feedback loop that monitors all LED pin
voltages to provide an output voltage just high enough
to light all LED strings. The LED current is regulated even
when VIN is greater than VOUT . The LED current can be
derated based on programmed LED temperature through
an NTC resistor divider or by programming die junction …