– Copied from customer email –
Are the GigaBlox Rugged M3 Mount Holes “Floating” or connected to Ground (GND) ?
Doesn’t say in the datasheet.
They are floating. In “nearly” all cases, we leave the holes on our boards floating. There is a bit of thought behind this decision.
In many electrical systems, there is often more than one reference plane or ground. In ethernet systems, the chassis is often tied to earth, which is a different connection point to power ground. There are advantages to doing this such as ensuring full galvanic isolation and preventing ground loops.
When we design our boards, we have to consider the multiple different ways in which a customer may integrate it into their system. Their system may use a single shared ground for everything (this is probably the most common), but some customers may also have the chassis of their device tied to a different connection as power ground.
In the latter case, connecting our mount holes to ground can cause an unwanted short between power ground and chassis ground.
The only benefit we saw of adding ground to mount holes is that it makes it easier to share a ground to the board without needing a power wire, but you need a power wire for the positive supply. So the downside of causing integration issues for our customers is larger than the minimal benefits of adding ground to the chassis, thus the holes are floating.
Caveat: Some of our boards use mount holes which have an unpopulated 0 Ohm resistor or solder jumper that allows the mount hole to be connected to power ground if needed. Typically this is only done in our larger boards where there is space to do so.