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I had to modify an older design that was put together years ago.
It seems that all of the power and ground pins on chips were not part of the individual component's schematic model and required opening the component's Properties window and assigning the nets under "SigPins". This is in PADs.
Was this ever a common practice? Sure, it can make the schematic look a little cleaner but if a technician were ever to look at the schematic to diagnose an RMA, how would they know what pins are connected to what rails?
It just seems like a really odd design and dangerous documentation choice. Or am I off-base and this is common?
- Comments(1)
A****min
Jul 09.2019, 17:31:04
One of my pet hates in schematics is having information that's essential to the operation of the design, but which can't be seen on a hard copy.
Hidden power pins are one example of this. Hiding power pins completely is a heinous crime; if you don't want them cluttering up a part of the design, split them out into a separate power & ground symbol, and put them on another page together with their decoupling caps.
Related crimes include calling a power net something like "VCC" instead of "+3V3", which tells the reader immediately what the supply rail voltage should be. The designer needs this information to be sure a chip is actually connected to the correct supply rail, and a technician may need the same information later on to tell whether or not a given supply is working correctly. Calling it something vague instead of stating the voltage explicitly is only OK if the supply voltage itself is variable, like the output of a solar panel, or a voltage which is altered at run time to trade CPU speed vs power dissipation.
There's a special circle in hell for designers who give the same net different names on different pages of the schematic, and expect the reader to navigate endlessly up and down their design's unnecessary hierarchy to keep track of which net is which.
