User`s guide

Specifyin
g
Di
g
ital Power Supplies 15
-7
Specif
y
in
g
Di
g
ital Power
Supplies
Digital power supplies are used to power interface subcircuits
that are automatically created by PSpice A/D when simulating
analog/digital interfaces. They are specified as follows:
• PSpice A/D can instantiate them automatically.
• You can create your own digital power supplies and place
them in the schematic.
When using parts from the standard libraries in your schematic,
you can normally let PSpice A/D automatically create the
necessary digital power supply.
Because digital power supplies are used only by analog/digital
interface subcircuits, digital power supplies are not needed for
digital-only schematics. It is recommended to avoid placing a
power supply to a digital-only schematic because it may
increase simulation time and memory usage.
Default Power Suppl
y
Selection
b
y
PSpice A/D
When PSpice A/D encounters an analog/digital interface, it
creates the appropriate interface subcircuit and power supply
according to the I/O model referenced by the digital part. The I/
O model is specific to the digital part’s logic family. The power
supply provides reference or drive voltage for the analog side of
the interface.
By default, PSpice A/D inserts one power supply subcircuit for
every logic family in which a digital primitive is involved with
an analog/digital interface. These power supply subcircuits
create the digital power and ground nodes which are the defaults
for all devices in that family. If multiple digital primitives from
the same logic family are involved with analog/digital
interfaces, one instance of the power supply subcircuit is created
If you use custom di
g
ital parts
created in technolo
g
ies other
than those provided in the
standard Model Library, you may
need to create your own di
g
ital
power supplies.