User`s guide

Input/Output Characteristics 7
-19
TSWLH
n
and TSWHL
n
These switching times are subtracted from a device’s
propagation delay on the outputs which connect to interface
nodes. This compensates for the time it takes the DtoA device to
change its output voltage from its current level to that of the
switching threshold. By subtracting the switching time from the
propagation delay, the analog signal reaches the switching
threshold at the correct time (that is, at the exact time of the
digital transition). The values for these model parameters should
be obtained by measuring the time it takes the analog output of
the DtoA (with a nominal analog load attached) to change to the
switching threshold after its digital input changes. If the
switching time is larger than the propagation delay for an output,
no warning is issued, and a delay of zero is used.
When creating your own digital device models, you can create
I/O Models like these for the primitives you are using.
MicroSim recommends that you save these in your own custom
model library, which you can then configure for use with a given
schematic.
Note
The switchin
g
time parameters are not used when
the output drives a di
g
ital node.
Table 7-2
Digital I/O Model Parameters
UIO Model
Parameters
Description
INLD input load capacitance
OUTLD output load capacitance
DRVH output high level resistance
DRVL output low level resistance
DRVZ output Z-state leakage resistance
INR input leakage resistance
TSTOREMN minimum storage time for net to be
simulated as a charge
TPWRT pulse width rejection threshold
See the online MicroSim PSpice
A/D Reference Manual
for more
on units and defaults for these
parameters.