Hello,
I designed a board which drives an LCD panel. It got 4 voltage rails (+1V8, +5V7, -5V7, +36V). Every one of those work fine except the +36V rail.
I choose the LP8867 as an LED driver to drive 2x5 white LED's (2 parallel 5 series). Unfortunately it doesn't work on the LCD panel I chose. I attached the backlight schematic for the panel aswell as the board and the schematic.

The LP8867 has 4 current sinks, of which I only use 2. I broke out the 2 cathodes and tried to drive regular white through-hole leds. They flicker 1 time and then they light up as expected. Nothing wrong here.

I power the whole thing with a bench power supply at +5V capped at 2A.

But when I attach the LCD panel the backlight doesn't turn on. Sometimes if flickers a few times (which assures me that the pinout is correct), but it never gets stable. When I measure the voltage on the +36V pad, it measures around +30V. I'm certain that the LCD panel work, because I have another board (not made by me) on which I can test them. I copied the voltage generation circuit from that known good board, but with a different yet pin compatible IC (TPS61194).

Again, the problem is that the LCD sometimes flickers the backlight, but it never turns fully on.

Any ideas are appreciated

 

An update: The problem are the contacts on the bottom of the LCD connector (top of the board.png). As you can see in the picture, the metallic almost cover the entire bottom. The problem now comes with the vias "between" the connector. The vias were not covered by soldermask, and so the contact is exposed under the connector. Thus, a few connections short with the ground vias under.

I designed a board without the vias below the connector and it works flawless.