ADD5211 String fail

Hey all!

Some time ago I was looking for a backlight driver solution and successfully use the ADD5211 now.
We've made over 100 PCBs using the circuit and today one came back which doesn't work anymore.

The ADD5211 goes into faulty state and stops working.

I've measured the string voltages, all but one are around 46V, the faulty string is around 2.3V (probes on the LED driving voltage right after the Schottky diode and each feedback pin of the ADD)

What can cause a single string to fail? I suppose the ADD5211 on the PCB itself is faulty, the LCD panel work with another board.

Could this be caused by a too warm environment?

Thanks for any advice and with best regards,

Robert

  • I tried to contact Analog customer service but they have no time. They suggested asking here, I did that over a week ago.

    It seems that 2 more backlight drivers became faulty, currently they are on the way to us. Both were built into displays which usually run in a cooler environment compared to the faulty board mentioned in the first posting.

    I still have no idea why a string would fail, it's not even running at the maximum string current ...