Tool/software:
Hi,
I have a daughterboard which uses LMH6881 devices. When tested on the bench (not fitted to end-use mother board) the devices operate correctly. However, when it is fitted to the motherboard it is designed for, we have a couple of boards where the LMH6881's get extremely hot and draw a lot of current.
I have not investigated this fully as of yet, however I wanted to ask if there has ever been any reported instances of this happening before, it seems like the characteristics of latch-up. This device only uses a single 5V rail, however the SPI communications in this context are derived from 3.3V logic, which I think could be active before the 5V is enabled (power sequencing), which I wonder if could be the cause.
Interestingly, while the devices are powered, the SPI bus still works, and I can read back data from them. Presumably the SPI communications "block" within the device is still operational.
The devices utilise the thermal bonding pad on the base. The boards have been fine when tested not fitted, but are showing these problems when fitted to the motherboard, and once removed and tested not fitted, continue to overheat, meaning something has permanently changed.
I still need to investigate further, but wanted to see if there is any information/advice that could help me get to the problem quicker.
Many thanks.
