Marc Murphy wrote on May 28th, 2006, 11:49am:Do I short the 1V pairs and short the gnd pairs, using a single 1 V supply? Or do I need 2 supplies each set at 1 V, connected to the core and IO pin pairs? If the latter is the case, I'm not clear on how ground is defined for the circuit. Don't the grounds need to be connected somewhere to have a common reference?
Thanks,
Marc
You can do either, but unless there is a very clear reason (different voltage or power supply isolation/crosstalk issues etc.) then both supplys and both grounds can come from one supply.
If you use seperate supplies, still it is often they will share the PCB ground reference.
Usually although a chip may have several grounds supplies, often each domain has a substrtae connections somewhere in the die, which nominally means each ground pins is connected together electrically via the substrate (in some chip power/ESD strategies one does NOT do this). Anyway, even though they have nominally the same potential, the grounds can still be isolated from one another in terms of impedance (by deep trenches, substrate isolation structures, phyiscal die distance).