Please see follow his description:
Until now we already assembled about 100 components, on 3 of them we found
problem and I start concern this could be a trend.
Three components do not functioning as suspected, (maybe they broken, maybe
they burned) see attached image – outside they look OK , we required
investigate where is a problem.
Problem was discovered only after hot-swap module testing.
Short explanation how we exercise these components:
These components (4 components per system) assembled on the backplane and
transfer unidirectional common I2C clock and data from the backplane to the hot
See part of backplane schematic attached.
VDD1 and SDA1 and SCL1 of each component connected on backplane all time ,
VDD2, SDA2, SCL2 are removable and connected only when module is connected
otherwise they are stay unconnected.
VDD2 power provided to the chip only from the module and following SDA2 and
In this type of application, the place we can have problems is ESD damage
during hot swapping. I suspect we will find ESD damage on one of the inputs. If
modules are connected on the fly, then there needs to be robust ESD control for
the I/O and power lines.