From: [email protected]
Date: Tue Aug 29 2000 - 13:19:30 PDT
Your dilemma has been shared for years by circuit designers (as opposed to
die-hard text editors). It is a painful task to draw schematics, assign
nodes, do extensive text entry (with all of the normal human errors in simple
transfer of the "picture" into text form), them type in all the related
commands, options, time steps, etc., etc., etc. If you are not prohibited
from using Windows-based programs (there is at least one large well-known
company that severely frowns on Windows ... guess who), there are a few
reasonably affordable programs you may find useful, and others that may make
you switch altogether.
I apologize in advance if the following dissertation offends anyone
(Engineers and vendors alike), but I make my living by quickly arriving at
correct answers that are also clearly communicable to both engineers and
managers. I recently (and successfully) completed a consulting task that
reduced the performance period by greater than 10:1 over using HSPICE for the
same design decisions.
I have both OrCAD Capture and Spectrum Software's Micro-Cap 6 (MC6) which
offer schematic entry, as does Intuit's ISPICE, Tanner's TSPICE (which claims
direct compatibility with HSPICE format), and I think Electronics Workbench
as well. Micro-Cap programs have included schematic entry for ~15 years
(which I think preceded most other SPICE-based programs by several years) and
OrCAD now ports into PSPICE. All save the human error problems that
represent perhaps 90% of the debugging time (of text-based entry) to simply
get a model running. (Note: Debugging was NOT an issue in the time saving I
noted earlier. There are many other Windows features that are conducive to
high productivity relative to UNIX-based programs.)
MC6 is based on SPICE and IMHO blows away the competition. It includes
analog and digital multimode simulation with schematic probing, plotting
DURING the run, performance plotting, 3D plotting, multidimensional stepping,
analog and digital behavioral modeling, an optimizing parts model generator,
BSIM devices, magnetics modeling, animated devices (e.g., LEDs), individual
device temperatures, Monte Carlo analysis with 3D statistical plotting (with
graded colors), and nearly automatic macro generation. You can enter or
import text SPICE files and run them if that is your choice (but alternate
model options are more efficient). An analysis dialog box allows you to
review and specify all simulation time periods, time steps, parameter ranges,
etc., and it writes the text lines automatically into the SPICE text file for
you (again, with no human errors and less time consumed). It directly exports
text netlist files to PSPICE or two versions of Berkeley SPICE (your choice)
and (with very minor semantic changes) will run in HSPICE. Note that PSPICE
or other netlists (with perhaps the exception of TSPICE) must also be altered
before they will run in HSPICE.
The MC6 schematic entry allows you to SEE your total schematic, with every
connection and every node (numbered for you automatically, without errors).
You can repetitively copy parts or entire sections of the circuit with
sequential part reference designators and node numbers added automatically
(again, no editing or errors). After a simulation, a mouse click can display
the voltages at all nodes or current or power in every device, or the B-field
strength in a coil, etc., etc., etc.
If you have complete SPICE circuits and called subcircuits (and who doesn't),
they can be imbedded into a macro and imported directly into an MC6 schematic
and mated with signal sources, passives, other digital or analog devices or
macros which can be in any of the modeling formats supported by MC6 (which
includes all SPICE formats as well). This mixed bag of models is efficiently
simulated with the latest Berkeley SPICE engine while outputting real-time
plotting displays of the analysis results.
The sophisticated, multicolored plotting subsystem allows waveform/curve
analysis with peaks, valleys, slopes, magnitude and time deltas, zoom
functions, automatic rescaling functions, individually selectable curve
widths, text weights, etc. And, the cursor always displays the time and
magnitude of any point on any curve you place it on.
The program allows plots to be captured in Windows metafile format (.wmf) and
embedded into the schematic, or (as I do) placed into PowerPoint and/or WORD
files for virtually universal (except perhaps at some companies where "Bill
Gates" is considered worse than a four-letter word) viewing by all interested
parties. The schematic can of course also be captured and transferred to
other Windows programs.
Like many other SPICE programs, MC6 does NOT (as yet) directly accept IBIS
files, but it DOES support tabulated models. I routinely extract equivalent
parameters from IBIS data and formulate MC6 models (e.g., drivers). The
clamp circuits are also easily extracted from IBIS data (takes 3-4 minutes to
build an equivalent Vcc/Vee clamp circuit model).
MC6 does not yet support coupled T-lines; however, if SPICE models or
cross-coupling equations (behavioral models) are available from other
sources, they can be imported and run successfully. Standard SPICE RLCG
T-lines, and telegraphers equations and equivalents are of course supported.
I recently imported and ran a (proprietary) Teradyne cross-coupled connector
model (received in HSPICE) that had over 2000 equivalent components without a
Many SPICE programs are node or memory limited. The only limit to MC6 is the
memory installed on your machine; i.e., RAM plus hard drive. I have
successfully run large simulations (upwards of 5000 nodes with 1.75 GBytes
resultant data) without problems.
Although I haven't compared prices in the last year, the cost for the various
programs varies widely. I think Electronics workbench goes at $1k. MC6 is
at $3.6k, and the others go from $5k to >$12k, depending on the tack-ons you
want. MC6 is an integrated, schematic/file entry, >12k model library,
simulation/analysis, and plotting program; i.e., no tack-ons. Most of these
include free upgrades for a year and may only cost a pittance ($500 to $1k)
for a major upgrade (PSPICE may be more).
Hope the above didn't bore or offend anyone,
Michael L. Conn
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