clipka wrote:

> According to JEDEC,
> 
> VCC = logic power voltage, serving as a reference for high signal levels 
> (often sharing a common rail with VDD, in which case they may be used 
> interchangeably).
> 
> VDD = drain power voltage. separate (positive) power rail to drive the 
> chip's internals.
> 
> VSS = GND = ground reference / source power voltage, serving as both 
> (negative) power rail and low signal level reference.
> 
> VSSQ = GNDQ = output stage source power voltage / ground reference, 
> serving as both a (negative) power rail and low signal level reference 
> specifically for output signals (should always be at the same level as 
> VSS=GND).

Suddenly the picture becomes even more complex than you feared...

> (This is just a subset of all the symbols used; for instance, 
> digital/analog devices such as programmable amplifiers or ADCs/DACs 
> often use separate voltage rails for the analog signals.)

Thank god I don't have to deal with anything analogue yet! ;-)

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