2 Conventional Backlighting vs. Local-Dimming backlighting

There are two types of technologies for controlling the dimming and brightness of an LCD screen, conventional and local dimming. In conventional backlighting black is reproduced as dark gray and details are lost in the shadows. With local dimming techniques, backlighting is optimized for specific areas of the image, resulting in deeper blacks. A local-dimming backlight technology is a direct-lit architecture where the LEDs are directly behind the LCD panel as shown in Figure 2-1.

In local dimming backlight, the LCD panel is divided into many small “zones”. The brightness of each zone is adjusted according to different display content. A local dimming backlight allows the display to have “darker blacks” and “brighter whites”.

To optimize the control of the brightness of these small zones, temperature feedback is critical to provide to the system. The LP8869-Q1 has two pins $T_{\mathrm{SET}}$ and $I_{\mathrm{SET}}$ that can be used in concert with thermistor divider circuits to provide thermal information to the system and allowing for a thermal foldback profile for the LED’s, limiting the amount of current after a certain temperature threshold thus protecting them.