Difference between revisions of "LTspice Genealogy - The Heritage of Simulation Ubiquity"
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== 1971: SPICE 1 (Simulation Program with IC Emphasis) - direct outgrowth of CANCER == | == 1971: SPICE 1 (Simulation Program with IC Emphasis) - direct outgrowth of CANCER == | ||
* Ron Rohrer leaves UC Berkeley and further development of CANCER (renamed SPICE) became Larry Nagel's Masters project with Don Pederson taking over as faculty advisor | * Ron Rohrer leaves UC Berkeley and further development of CANCER (renamed SPICE) became Larry Nagel's Masters project with Don Pederson taking over as faculty advisor | ||
− | * '''''KEY EVENT:''''' Don Pederson insisted that all further work be releasable to the public domain | + | * '''''<font color="green">KEY EVENT:</font>''''' Don Pederson insisted that all further work be releasable to the public domain |
* SPICE 1 release's key features: | * SPICE 1 release's key features: | ||
** Models for bipolar transistors were changed to Gummel-Poon equations | ** Models for bipolar transistors were changed to Gummel-Poon equations | ||
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* Was the first commercial offspring of Berkeley SPICE to run directly on the PC platform | * Was the first commercial offspring of Berkeley SPICE to run directly on the PC platform | ||
* Was the first SPICE program to gain wide acceptance in both industry and academia | * Was the first SPICE program to gain wide acceptance in both industry and academia | ||
− | * '''''KEY EVENT:''''' A zero cost (but node-limited) student version is introduced in 1988 | + | * '''''<font color="green">KEY EVENT:</font>''''' A zero cost (but node-limited) student version is introduced in 1988 |
** For the first time, SPICE becomes truly ubiquitous in the electrical engineering community | ** For the first time, SPICE becomes truly ubiquitous in the electrical engineering community | ||
* Evolved from Berkeley SPICE 2G, but added many proprietary enhancements | * Evolved from Berkeley SPICE 2G, but added many proprietary enhancements | ||
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* Schematics, a graphical front end, was added much later sometime in the early 1990s | * Schematics, a graphical front end, was added much later sometime in the early 1990s | ||
− | == The Road To <font face="serif" font color="red" size="+2"> | + | == The Road To '''<font face="serif" font color="red" size="+2">LTspice IV</font>''' == |
* 1991 DOS SwitcherCAD available from LTC (equation based) | * 1991 DOS SwitcherCAD available from LTC (equation based) | ||
* 1992 First ever port to Linux of SPICE (3E2) publicaly released by Mike Engelhardt | * 1992 First ever port to Linux of SPICE (3E2) publicaly released by Mike Engelhardt |
Revision as of 17:10, 19 July 2013
Contents
1969: Beginnings of CANCER (Computer Analysis of Nonlinear Circuits, Excluding Radiation)
- CANCER began as a derivative of a program that was the class project of a series of courses taught by Ron Rohrer with the approval and encouragement of Professor Donald O. Pederson
- Larry Nagel wrote the netlist parser and the analysis core and was student group leader
- Lynn Weber developed a noise analysis feature that utilized adjoint network techniques
- Bob Berry wrote the sparse matrix LU decomposition package
- CANCER project's key features:
- Was the first circuit simulator to utilize sparse matrix techniques
- Used Newton-Raphson iteration method heuristically modified for bipolar circuits
- Utilized implicit integration to accommodate widely spread time-constants of an IC
- Integrated DC operating point analysis, small-signal AC analysis and transient analysis
- Project presented by Ron Rohrer at the 1971 ISSCC[1], but the code was considered partially proprietary and was never publicly released
1971: SPICE 1 (Simulation Program with IC Emphasis) - direct outgrowth of CANCER
- Ron Rohrer leaves UC Berkeley and further development of CANCER (renamed SPICE) became Larry Nagel's Masters project with Don Pederson taking over as faculty advisor
- KEY EVENT: Don Pederson insisted that all further work be releasable to the public domain
- SPICE 1 release's key features:
- Models for bipolar transistors were changed to Gummel-Poon equations
- JFET and Shichman-Hodges MOSFET devices added (for Dave Hodges' MOSFET design class)
- Fixed time step and strict Nodal Analysis (true voltage sources and inductors not supported)
- DC, AC, Transient, Noise, and Sensitivity Analyses in the same program
- Built-in models for diodes, bipolar transistors, MOSFETs, and JFETs
- Was about 6k lines of FORTRAN at first informal limited public release in late 1971
- Official public release was May 1972 with first formal paper presented by Don Pederson at the 16th Midwest Symposium on Circuit Theory, April 12, 1973
- SPICE 1 becomes industry standard simulation tool running on large mainframe computers
1972: SPICE 2 begins
- First version of SPICE 2 was Larry Nagel's Ph.D. project under Don Pederson
- Modified Nodal Analysis (MNA) added, enabling voltage sources and inductors for the first time
- Ellis Cohen added dynamic memory allocation
- Adjustable time-step control added, greatly speeding most simulations
- MOSFET and bipolar models overhauled and extended
- Was about 8k lines of FORTRAN when first released to the public domain in late 1974
- Larry Nagel departs for Bell Labs and his thesis becomes the de facto SPICE 2 Users Guide
1975: Journey to SPICE 2G6 (the pinnacle FORTRAN version)
- Ellis Cohen becomes primary contributor with later help from Andrei Vladimirescu
- First of a series of public revision releases after Nagel's version 2B begin in 1978
- Along the way, sub circuits, poly sources and transmission lines are added
- Version 2G6 ends up implementing three MOSFET models:
- MOS 1 is a simplistic model described purely by ideal square-law I-V characteristics
- MOS 2 is an analytical model, MOS 3 is a semi-empirical model and both include second-order effects such as channel length modulation, sub threshold conduction, scattering limited velocity saturation, small-size effects, and charge-controlled capacitances
- 2G6 released to public domain in April 1983 (and is still available today from UC Berkeley)
- Many current commercial simulators are based on SPICE 2G6
1983: SPICE 3 begins
- Tom Quarles begins work, writing first version in RATFOR, a C-like preprocessor for FORTRAN
- Was fully converted to C in 1985 with first early versions released in March of that year
- Added models: MESFET, lossy transmission line and non-ideal switch
- Arbitrary behavioral voltage and current sources added
- Includes polynomial capacitors, inductors and voltage controlled sources
- Allowed the use of alphabetical node labels rather than only numbers
- Features a graphical interface for viewing results
- New version eliminates many convergence problems
- Added noise, distortion and pole-zero analysis, temperature sweeping, Monte Carlo and Fourier analysis
- Not fully compatible with SPICE 2G6
- Was about 135,000 lines of C code at first public release in 1989
- Final version at Berkeley, SPICE 3F5, released to public in 1993
- XSPICE was developed at Georgia Tech as an extension to the SPICE language to allow behavioral modeling of components
- Drastically improve the speeds of mixed-mode and digital simulations
1984: PSpice (micro Processor SPICE)
- Developed by MicroSim to run on the first IBM PC, initially released in January 1984
- Was the first commercial offspring of Berkeley SPICE to run directly on the PC platform
- Was the first SPICE program to gain wide acceptance in both industry and academia
- KEY EVENT: A zero cost (but node-limited) student version is introduced in 1988
- For the first time, SPICE becomes truly ubiquitous in the electrical engineering community
- Evolved from Berkeley SPICE 2G, but added many proprietary enhancements
- Probe, a waveform viewer module, was added when PC VGA graphics became available
- Schematics, a graphical front end, was added much later sometime in the early 1990s
The Road To LTspice IV
- 1991 DOS SwitcherCAD available from LTC (equation based)
- 1992 First ever port to Linux of SPICE (3E2) publicaly released by Mike Engelhardt
- 1994? Development at LTC of in-house advanced simulator begins based on Berkeley SPICE 3F4/5
- Code extensively revised to improve performance on machines with faster processors than memory
- Vastly improved convergence and time step control over that of Berkeley SPICE
- Added support for important industry standard device, model and behavioral extensions
- 1996 μPower SwitcherCAD available from LTC (simulation based)
- Proprietary mixed-mode HDL capability added to LTC's in-house simulator
- Efficiently handles extremely tight feedback between analog and digital sections
- Greatly reduces node count in switched-mode IC macro models
- 1998? SwitcherCAD released for internal review at LTC
- Decision made to extend PSpice syntax recognition to simplify user support and ease of use with existing models
1999: LTspice/SwitcherCAD III first released to public
- LTC's Field Application Engineers received the very first copies of LTspice in October
- FAEs were then free to give LTspice to customers they met on a visit-by-visit basis
- June 2001, now a web-based download, LTspice becomes widely publicized in trade journals and engineering forums
- LTspice/SitcherCAD III key features:
- Includes P-SPICE compatible semiconductor, device and syntax model extensions
- Diode recombination current, bipolar quasi-saturation and JFET deep impact ionization
- Behavioral modeling (legacy 2G6 POLY statements, arbitrary expressions, Laplace, and look-up tables)
- Includes an original mixed mode simulator with native digital library (not X-SPICE based)
- Inductors and capacitors come with extensive built-in parasitics available, yet don't cost any extra nodes
- New arbitrary capacitance device (user inputs charge expression)
- Is internally symbolically differentiated and then capacitance is integrated
- Initial release extends MOSFET model support to BSIM 3.2.2 and BSIM 4.1 (BSIMPD 2.2 and EKV 2.6 followed shortly thereafter)
- Also includes a native power VDMOS device model with integral nonlinear interelectrode capacitances
- Waveform viewer with marching waveforms and dynamic waveform data compression
- Built-in device library/database (includes many power MOSFETs, diodes, bipolars, JFETS and switch-mode controllers)
- Built-in program update checker (bug fixes and feature additions available in near real time)
- Includes P-SPICE compatible semiconductor, device and syntax model extensions
Important Follow-on Enhancements
- KEY EVENT: In October 2001 the LTspice Yahoo users group is started by Ralph Reinhold
- Within the first year Helmut Sennewald takes over as moderator organizing one of Yahoo's most successful technical forums
- Includes over 30k members and rapidly approaching 100k messages (as of July 2013)
- More noteworthy bullet points to be added here shortly (raw change log items are listed below)
Feb02: Added preliminary support for ddt(), idt(), and idtmod() analog behavioral functions. May02: Implemented binning for all MOS and BSIM models. May02: Wave file I/O capability added. Jan03: Hierarchical schematics added. Jan03: A graphical symbol editor was introduced. Mar03: Keyboard short cuts are now user definable. Jun03: Added an alternate solver (uses a 1/2x slower but >1000x more accurate sparse matrix package). Jul03: Ability to export a netlist for PCB layout added. Aug03: Implemented differential cross probing (drag the mouse between two wires). Nov03: Probing of component instantaneous power dissipation added (alt-left click its symbol). Jan04: Added the ability to annotate waveform plots with graphics and text. Mar04: Windows meta file output support added. Apr04: Chan inductor, undocumented behavioral inductor revealed. Dec04: Implemented .measure commands. Feb05: .raw files can now be converted to a Fast Access format that allows new plot traces to be added. Jun06: Added continuous derivative level 2 devices to the ideal diode and voltage controlled switch. Nov07: There is now a diode instance parameter, N, that sets the number of devices in series. Other: ako, param stepping, unlimited undo and redo, parametric (x-y) plotting, amp and power meters, Fourier analysis (both .four statements and FFT's of simulated data)
2008: LTspice IV released
- "SwitcherCAD" is dropped from the name, simplifying the description and thereby emphasizing the general purpose nature of LTspice
- Key features added to LTspice IV:
- Multi-threaded solvers to better utilize current multi-core processors
- New SPARSE matrix solvers that deploy self-authoring code
- Code is assembled and linked on the fly
- Approaches the theoretical flop limit of current FPU's
- Large circuits run up to 3x faster on quad core processors
- KEY EVENT: With 3+ million copies downloaded, LTspice becomes, by far, the de facto standard SPICE program
- More noteworthy bullet points to be added here shortly (raw change log items are listed below)
Feb09: A symbol can now be automatically generated for a schematic. Apr09: The data from a .step'ed .meas statements can now be reformatted to a .raw file and plotted (View=>SPICE Error Log then right button menu). Jul09: Reimplemented MOS levels 1, 2, and 3 to use the Yang-Chatterjee charge model instead of the Meyer capacitance model and added warnings when using archaic MOS levels 1, 2, or 3 below reasonable dimensions. Sep10: The .op values can now be displayed on the schematic while plotting .ac or .noise data (schematic right button menu->View->Place .op Data Label). Dec11: The LTspice-Gummel-Poon now supports a parasitic PNP to accurately model the substrate behavior of a vertical NPN. Mar13: Added a level 73 MOSFET: HiSIM-HV from Hiroshima University and STARC.