RLE-TR-588-319047
Contents
1. ee ee es 3 4 3 Subcircuit Definitions 0 a eee ee ee Electrical iento alo aha 3 5 MOS Models rra A cd ce a paa ee eA Est cd 30 2 Bipolar Models A A eee hewn eae 3 9 3 Diodes rede tsa er Dee le a A Tak Bs 30 Lo Resistors cra dna A ere i Ee ee eye as Be AGED ACMLOT OS dr ter Sy ee ch vie oO tp td Ge ad hee Reda DS wlth EAR BRAS 3 5 6 Constant Current Source 3 5 7 Voltage Controlled Current Source 00002 ee eee 3 5 8 Constant Voltage Sources 2 ee ee 3 5 9 Piecewise linear Voltage Sources o 3 5 10 Sinusoidal Voltage Sources o ee ee Analysis and Control Statements 1 2 0 000 eee eee eee 3 651 Plot Statement tes such ea Ass le Re hh RUS ve a esa 3 6 2 Initial Conditions es 3 6 3 Simulation Options iii A SIMLAB Commands Q B g SIMLAB Variables Bale System Constante snes saroi oot iE SE Ae al a o B 2 Simulation Variables B 3 Functional Controls 0 eee ee ee ee ee eee Non Standard Supported Packages C 1 Iterative Methods for Linear System Solution Example Configuration File Example Session Example Circuit Files Example SIMLAB Session iv eee ee eee eee ee ee ee 33 43 43 43 49 ol 53 53 55 56 58 61 1 Introduction SIMLAB is a circuit simulation environment consisting of a flexible user friendly front end operating in conju2. 2 1 2 Plotting Currently viewing the results of a simulation run is done using a modified version of xgraph a two dimensional plotting package developed by D Harrison at U C Berkeley However if some local viewing program is available the user can override the use of xgraph by setting the environment variable SIMLAB PLOTTOOLS to point to the preferred plotting tool The environment variable SIMLAB PLOTARGS should also be set possibly with command line arguments for the plotting tool If no arguments are necessary the variable should still be set this can be acomplished from inside SIMLAB Note that the plotting tools must be able to read the simlab output format which consists of lines of the form node_name time voltage 2 2 Specifying algorithms in SIMLAB One of the most powerful features of SIMLAB when used for algorithm development is the ability to specify which numerical algorithms are used at different stages of the simulation For this purpose there are five basic predefined functional controls solve linear Specifies function to be used for linear system solution during simulation solve_nonlinear Specifies function to be used for nonlinear system solution during simu lation Key Action C a beginning of line C b backward char C d delete char C e end of line C f forward char C g keyboard quit TAB complete word C k kill line C
3. connected to internal base node SoS a6 4 wom a Da ges Table 7 Bipolar model parameters 24 name parameter units default typical kf af fc area ideal reverse transit time s zero bias collector substrate F capacitance substrate junction built in potential V substrate junction exponential factor forward and reverse beta temperature exponent energy gap for temperature effect on is eV temperature exponent for effect on is flicker noise coefficient flicker noise exponent coefficient for forward bias depletion capacitance formula area factor Table 8 Bipolar model parameters cont name parameter units examples area area factor m 1 Table 9 Bipolar Element parameters 25 parameters units default typical diode area saturation current Forward explotion current emission coefficient transit time thermal voltage zero bias junc cap junction potential grading coeff coeff of depletion cap in forward bias rev breakdown Table 10 Diode model parameters Diodes may be used anywhere and are typically used to represent source and drain junction effects on MOS devices In the element definition area is the area of the junction Model parameters are given in table 10 The parameter maz is used to bound the diode current to avoid numerical overflow It should be set to a value that well above a reasonable current for the diode 3 5 4 Resistors Resistors Model Defi
4. These packages are examples of the power fulness of SIMLAB as a tool for research in circuit simulation algorithms and are provided together with the standard distribution However to be able to use the functionality they provide SIMLAB must be told to incorporate these packages when building an executable This is accomplished by proper setup of the options provided in the config h configuration file The mentioned packages were built on top of SIMLAB and have been tested perhaps less frequently than the SIMLAB standard package they still run for at least one test case however The authors welcome any comments bug reports suggestions or enhancements to these packages as well as to the rest of the SIMLAB circuit simulation C 1 Iterative Methods for Linear System Solution This package is distributed under the relax subdirectory of the source code tree To have SIMLAB incorporate the functionality provided in this package you must define USE_RELAX in the config h configuration file of SIMLAB before building and installing the program Currently this package contains a series of algorithms for the iterative solution of linear systems Among these are e Gauss Jacobi relaxation gj e Gauss Seidel Relaxation gs e Kaczmark Relaxation km e Banded Relaxation vbr e Jacobi Over Relaxation methods jor e Seidel Over Relaxation methods sor e Conjugate Gradient cg Generalized Conjugate Residual gcr Conjugate Gradient Squ
5. To specify a parameter include the parameter name and the value separated by an equal sign The model parameters list can be in any order 3 4 2 Element Statements Element Statements General Form name nodel nodeN model or subcircuit name params Examples nmosl store input phase 1 0 mostran w 25u 1 1 5u gcapl input output c c 0 07p gate7 output outbar inverter The element definition statement consists of an element name the nodes connected to the element a model to which the element refers and optional parameters The element names can be the same as the model name or even as a node name but no two elements may have the same element name The number and order of the nodes must correspond to the model being referenced The model name can be either a user defined model a subcircuit or a SIMLAB low level model c r dc pwl i etc An element statement can also include parameters and will override the values given in the model statement MOS transistor elements can include the width w and length 1 parameters diodes can include the area factor and resistor and capacitor elements can include resistance and capacitance values As with the model statement parameters should be listed as a name value pair separated by 3 4 3 Subcircuit Definitions The subcircuit defines a macro which can be expanded in the circuit any number of times When an element statement refers to a subcircuit definition t
6. Without an argument cd changes to the user s home directory The cd command understands the csh style of shorthand for pathnames circuit circuit Purpose Load a circuit file for simulation Synopsis circuit filename Description circuit loads a circuit into SIMLAB for simulation filename must be a valid file name Some application variables will be affected by the circuit file Diagnostics The input circuit file must be specified in SIMLAB format See Section 3 for more information 33 continue continue Purpose Continue simulation run Synopsis continue Description continue allows the user to continue a simulation run from the present time until stop This is useful when a run is made and the stop time increased or when a run is interrupted Transient simulations started with continue begin at time t PresentTime and end at time t stop Diagnostics If the present time equals the stop time continue does nothing If continue is issued without a previous run a run is executed 34 diary diary Purpose Record the session in a file Synopsis diary on off filename Description The diary command saves the entire SIMLAB session in ascii format in file filename If no filename argument is specified the session is saved in ascii format in the file diary doc The argument off will temporarily suspend diary operation until diary on is issued The diary command
7. dc direct sparse Gaussian elimination tran direct sparse Gaussian elimination Default de direct tran direct solve_nonlinear Description Specifies function to be used for nonlinear system solution during simulation Dif ferent functions can be specified for DC and Transient simulation Values dc newton Newton Raphson iteration tran newton Newton Raphson iteration Default de newton tran newton 49 Description Specifies which integration method to use Has no meaning except in transient mode Values tran trap trapezoidal integration tran gear2 second order backward difference integration tran beuler backward Euler integration tran feuler forward Euler integration Default tran trap simulate Description Specifies what type of simulation structure to use Different functions can be spec ified for DC and Transient simulation Values dc pt pointwise solution in time tran pointwise solution in time Default dc pt tran pt 50 environment Description Specifies what type of environment SIMLAB was built for Different environments cannot be specified for DC and Transient simulation The value reflects the nature of the underlying hardware and is therefore likely to suffer little if any changes The notion of environment is included to allow expandability to different computer architectures such as was done
8. 1 performs dc solution If zero no dc solution is performed default dodc dotran 1 If equal to 1 performs transient analysis If zero no transient analysis is performed cmin le 18F Sets the minimum capacitance to ground Only used in the dc solution Should not be set to zero gmin Inmho Sets the minimum conductance to ground Only used in the dc solution Should not be set to zero nrvabs ImV sets the Newton Raphson absolute voltage tolerance nrvrel 0 001 Sets the Newton Raphson relative voltage tolerance nrcabs le 9 Sets the Newton Raphson absolute current tolerance nrcrel 0 001 Sets the Newton Raphson relative current tolerance maxdenr 200 Sets the number of newton iterations used before giving up in the de solution maxnr 10 Sets the number of newton iterations used before giving up in the transient solution nralpha 0 3V Sets the maximum voltage step to use in newton iteration newjacob 3 Number of newton iterations used before reevaluating the jacobian in the transient analysis lteabs 5m Sets the absolute local truncation error lterel Sets the relative local truncation error Table 11 SIMLAB program simulation options and default values 31 32 A SIMLAB Commands cd cd Purpose Change current working directory Synopsis cd pathname Description cd changes the current working directory i e the starting point for pathnames not beginning with
9. 5 Level 3 MOSFET model parameters cont name parameter units examples channel width m l channel length m 1 54 as area of source region m 100p ad area of drain region m 100p ps perimeter of source region m 40u pd perimeter of drain region m 40p number of squares source res calc 0 number of squares source res calc 0 Table 6 Level 3 MOSFET element parameters 23 name parameter units default typical Is transport saturation current bf ideal maximum forward beta nf forward current emission coefficient forward Early voltage corner for forward beta high current roll off B E leakage saturation current B E leakage emission coefficient ideal maximum reverse beta reverse current emission coefficient reverse Early voltage corner for reverse beta high current roll off B C leakage saturation current nc B C leakage emission coefficient rb zero bias base resistance irb current where base resistance falls halfway to its min value rbm minimum base resistance at high currents emitter resistance collector resistance B E zero bias depletion capacitance B E built in potential B E junction exponential factor ideal forward transit time coefficient for bias dependence of tf voltage describing vbe dependence on tf high current parameter for effect on tf excess phase at f zr Hz B C zero bias depletion capacitance B C built in potential B C junction exponential factor fraction of B C depletion capacitance
10. 6 lambda 0 02 model pulldn pmos3 vto 1 12 gamma 0 266 kp 79u phi 0 6 lambda 0 02 load1 vdd output output 0 pullup w 5u 1 20u pulldn 1 output outbar 0 0 pulldn w 10u 1 5u The model parameters used in MOS Level 3 are listed in table 4 The element parmeters for the MOS 3 model are listed in table 6 3 5 2 Bipolar Models There is a BJT model that can be used to simulate circuits with bipolar transistors with the SIMLAB program This model is an adaption of the integral charge control model of Gummel and Pool with extensions that include several effects of high bias levels 19 parameter units default typical default width for elements default length for elements default source area for elements default drain area for elements default source perimeter for elements default drain perimeter for elements bulk threshold parameter surface potential lambda channel length modulation vto zero bias threshold voltage kp transconductance parameter tox gate oxide Thickness cgso gate source overlap capacitance per unit channel width cgdo gate drain overlap capacitance per unit channel width cgbo gate bulk overlap capacitance per unit channel width fc coefficient for forward bias depletion capacitance formula js bulk junction saturation current per sq meter of junction area mj bulk junction bottom grading coef bulk junction sidewall grading coef cj zero bias bulk junction bottom cap per sq meter of junction area zero bias bulk
11. as ground The first node in the global node list is assumed by SIMLAB to be the ground node and should be so specified There is no other constraint on the order of the nodes in the list 3 4 General Form for Model and Element Statements Notation In the following description data fields that are enclosed in brackets and are optional Names enclosed in and Y should be replaced by alphanumeric strings and value fields should be replaced with numbers All indicated punctuation is required Associated reference directions are used positive current flows in the direction of most positive to most negative 3 4 1 Model Statements Model Statement General Form model name type namel value name2 value Examples model nmosl nmos vto 2v kp 15u gamma 0 model cstray c c 0 025pf 15 This statement describes a model in the circuit Element statements refer to this statement to obtain parameter values associated with the element The model statement must begin with the word model The next field is the model name which is used to refer to the model in the rest of the circuit description The third field is the model type This should be the name of an internal SIMLAB model r c nmos pmos nmos3 pmos3 d etc If there are parameters they should be listed at the end of the model statement All unlisted parameters will be set to the default value for the model type See next section
12. from the circuit file that change affects only the current value although it remains in effect until a new value is given at the command line or a new circuit is read This means that reading in circuits that explicitely contain commands to change the value of some of SIMLAB s variables will not affect subsequent runs of other circuit since the variables are reset to their default values before a new circuit is read into SIMLAB However setting the value of a variable at the command line changes the actual default value of the variable for the entire SIMLAB session Description The current value of time in the simulation run time is set to zero when run is issued and should be set to stop when a simulation run is completed normally Description Minimum value of capacitance to ground at each node Should not be set to zero Default 1 0e 18 F Description Boolean variable specifying whether or not to conduct a dc simulation If dode and dotran are both set to True the dc simulation is conducted first and the solution is used as the initial condition for the transient simulation Default True 44 Description Boolean variable specifying whether or not to conduct a transient simulation If dodc and dotran are both set to True the de simulation is conducted first and the solution is used as the initial condition for the transient simulation Default True Description Minimum condutance to ground at eac
13. is used to describe general parameters for the SIMLAB elements and many elements of the same type may refer to a single model statement Each model defini tion must include an external reference name the name of a primitive model type and the appropriate model parameters For example model BusMos nmos vio 0 8v kp 20u gamma 0 8 phi 0 6 defines the model for an enhancement NMOS transistor with 0 8V threshold The circuit topology is specified using element statements Each SIMLAB element statement must include a name for the element a list of node names and a reference to a model Soa BusMos transistor named dWrite2 whose substrate is grounded is clocked by signal PHI2 and connects nodes latchOut to DBus would be defined by dWrite2 latchOut PHI2 DBus 0 BusMos 11 3 1 2 Subcircuits and Parameters The SIMLAB circuit parser also supports hierarchical circuit descriptions through the use of subcircuits A subcircuit is like a program macro in the sense that the subcircuit is first defined and then each time it is referred to the definition replaces the reference The general form for a subcircuit definition is the keyword define followed by a subcircuit name and then a list of nodes enclosed in parentheses The element statements that describe the subcircuit follow the define statement and the subcircuit is terminated with an end statement For example an inverter subcircuit could be described as follows d
14. rel Reading boot rel stop 1 250000e 07 cmin 1 000000e 14 lterel 5 000000e 04 lteabs 5 000000e 06 dodc 0 gt Y Make sure to do DC solution gt dodc 1 dodc True gt Use direct methods for linear solution gt set solve linear direct gt Use 2nd order backwards differentiation integration formula gt set integrate gear2 gt Run gt run 56 Example Simlab session cont Simulating circuit boot rel DC Simulation Results Sun Oct 14 01 12 50 1990 Simulation Method DC Solution Time Nonlinear Solution Method DC Newton Iterations Linear Solution Method Initial Decomposition Time Linear Solution Time sobolev Pointwise Solution 0 Newton 23 Direct 0 0 Transient Simulation Results Sun Oct 14 01 12 51 1990 Simulation Method Transient Solution Time Integration Method Timesteps Nonlinear Solution Method Newton Iterations Linear Solution Method Initial Decomposition Time Linear Solution Time sobolev Pointwise Solution 966667 2nd Order Gear 231 Newton 362 Direct 0 0 0666667 gt Plot the results on the display gt plot gt Y Done gt diary off gt quit 57 F Example Circuit Files A simple boot strapped inverter is illustrated below bootinv rel SIMLAB Boot strapped inverter example Required global statement to indicate ground node global 0 Transistor model parame
15. will also save output generated by programs run with escapes to the shell Diagnostics Diary uses tee to capture output produced by programs run in an inferior shell Some programs in particular 1s have a different format when directing output to a pipe instead of to the standard output 35 help help Purpose Provide help Synopsis help item Description help provides help When invoked without an argument help provides a list of possible help topics When invoked with an argument help provides information on that specific topic Diagnostics At present help can only list possible help topics On line help will be enhanced in future releases history history Purpose List previous command lines Synopsis history Description history lists the lines entered into SIMLAB for review by the user Previous lines can be accessed with successive applications of the C p key see Section 2 1 1 36 plot plot Purpose Plot the circuit output Synopsis plot Description plot causes all the nodes specified in the circuit input file using the circuit description file plot directive which is distinct from the SIMLAB plot command to be plotted See Sections 2 1 2 and 3 6 1 Diagnostics SIMLAB effects this command by forking and calling an appropriate plot program for its host environment Presently only the X windows version 11 environment is supported At this time all the nodes specified by th
16. 17u ps 17u ma2 7 2 5 0 sqshare w 7u 1 3u ad 10 5p as 10 5p pd 17u ps 17u ma3 3 1 8 0 sqshare w 7u 1 3u ad 10 5p as 10 5p pd 17u ps 17u ma4 8 2 5 0 sqshare w 7u 1 3u ad 10 5p as 10 5p pd 17u ps 17u 9 5 maS 4 9 3 0 nqshare w 7u 1 3u ad 56p as 10 5p pd 30u ps 17u mnphi 5 10 0 O sqshare w 7u 1 3u ad 10 5p as 56p pd 17y ps 30u 59 domino rel cont Output buffer m7 6 4 100 100 pqshare w 7u 1 3u ad 56p as 56p pd 30u ps 30u m8 6 4 0 O sqshare w 7u 1 3u ad 56p as 56p pd 30u ps 30u Constructed complex p and n channel models model nmod nmos vto 0 8 kp 35u gamma 0 2 phi 0 55 lambda 0 02 cgso 1 4e 10 cgdo 1 4e 10 cgbo 2 4e 10 tox 500e 10 model pmod pmos vto 0 8 kp 14e 6 gamma 0 37 phi 0 61 lambda 0 01 cgso 2 1e 10 cgdo 2 1e 10 cgbo 2 4e 10 tox 500e 10 Diode models model npdmod d is 3e 9 cjo 0 73e 10 m 0 33 model nadmod d is 3e 9 cjo 0 77e 4 m 0 5 model ppdmod d is 1e 9 cjp 2 2e 10 m 0 33 model padmod d is 3e 9 cjo 1 4e 4 m 0 5 Define nqshare and pqshare subcircuits define nqshare d g s b parameters w 10u 1 5u as 1 0 ad 1 0 ps 10 pd 10 device d g s b nmod w w 1 1 dsp bs npdmod area ps dpd bd npdmod area pd dps bd nadmod area as dpd bd nadmod area ad end nqshare define pqshare d g s b parameters w 10u 1 5u as 1 0 ad 1 0 ps 1 0 pd 1 0 device d g s b pmod w w 1 1 dpd db ppdmod area ps dps sb padmod area as dpd db padmod area ad end pqshare 60 Ali in EDE HES Simulation of circ
17. Description Boolean value False Can be used with boolean simulation variables e g dodc False False is equivalent to integer value zero Description 3 14159 B 2 Simulation Variables These variables are used for controlling various aspects of the simulation You will most likely only need to change those variables which are necessary to specify the type of sim ulation desired e g stop dodc or dotrans In general the default values of the other variables will work well Tf convergence problems are encountered you may wish to adjust some see Sections 2 3 and 2 4 In the current release of SIMLAB all variables can be changed by the user when interacting with the front end Some of them however can also be set from the circuit file SIMLAB has the notion of default value of a variable and current value of a variable Changes in the default or current values of SIMLAB s variables adhere to the following conventions 1 all changes to values of SIMLAB s variables affecting either their default or current values are shown to the user 2 before any circuit is read into SIMLAB the current values of all SIMLAB variables are reset to their default values 43 3 if the value of a SIMLAB variable is set at the command line that change affects both the default and current values of that variable furthermore the new value becomes the new default value for the entire session 4 if the value of a SIMLAB variable is set
18. PURPOSE OR THAT THE USE OF THE LICENSED SOFTWARE COMPONENTS OR DOCUMENTATION WILL NOT INFRINGE ANY PATENTS COPYRIGHTS TRADE MARKS OR OTHER RIGHTS M LT shall not be held liable for any liability nor for any direct indirect or consequential damages with respect to any claim by LICENSEE or any third party on account of or arising from this Agreement or use of this software Contents 1 Introduction 2 A SIMLAB Primer 2 1 2 2 2 3 2 4 3 The 3 1 3 2 3 3 3 4 3 5 3 6 The SIMEAB Front End vay benden Wade eos eS deh eee oR 2 1 1 Command Line Editing is eae eda ek We aen ea Se Zele A co ence path a ake Rek ande tang hd ty ere We sa Specifying algorithms in SIMLAB 20 Warnings about the Algorithms used in the SIMLAB Program Hints on Convergence neee te ee Circuit File Fundamentals on wet heten eet and acces WP ln ee a ee ee Re 3 1 1 Models and Elements 2 0 00 cee eee ee eee 3 1 2 Subcircuits and Parameters 0 0 00 0000 ee ues 3 1 3 Locals and Globals 2 0 0 0 0 02 ee ee ees 3 1 4 Control Statements 2 e a 3 1 5 Initial Conditions and the DC Solution 3 16 Comments sate dem Vn eae hoe Ate wR lg A Erin Basie Language Rules sa aa wld aanried Ae wee we alae a US Choosing Node Names eis aa ene LN a a General Form for Model and Element Statements 3 4 1 Model Statements 00 cee ee ee ee eee 3 4 2 Element Statements
19. SIMLAB User s Guide M Silveira A Lumsdaine J White RLE Technical Report No 588 December 1994 The Research Laboratory of Electronics MASSACHUSETTS INSTITUTE OF TECHNOLOGY CAMBRIDGE MASSACHUSETTS 02139 4307 This work was supported in part by the National Science Foundation under Grant MIP 91 17724 SIMLAB USER S GUIDE M Silveira A Lumsdaine J White Research Laboratory of Electronics Department of Electrical Engineering and Computer Science Massachusetts Institute of Technology Cambridge MA 02139 Draft of December 12 1994 Abstract This manual describes how to use the SIMLAB circuit simulator for verifying the electrical behavior of circuits SIMLAB is a circuit simulation environment consisting of a flexible user friendly front end operating in conjunction with a sophisticated and versatile simulation engine The program is specifically designed to be used as an educational tool and as a research platform SIMLAB can be operated in either batch or interactive mode The user is allowed to separately specify algorithms for the various aspects of the simulation in cluding the simulation environment ODE system solution type numerical integration method nonlinear algebraic and linear system solution methods Furthermore SIMLAB is also designed to be easily customized for research purposes Researchers can easily construct and test algorithms by inserting them into the existing SIMLAB framework For in
20. Synopsis setenv env_var val Description With no arguments the setenv command displays all UNIX environment variables With the env_val argument it sets the environment variable env_var to have an empty null value By convention environment variables are normally given upper case names With both env_var and val arguments setenv sets the environment variable env var to the value val which must be either a single word or a quoted string When SIMLAB is started all the environment variables currently set are automatically imported to the sIMLAB UNIX environment Setting a new variable or reseting the value of an existing variable affectes the UNIX erivironment of SIMLAB but not that of its father process 39 sh sh Purpose Execute shell command Synopsis sh command Description sh executes its arguments using an inferior shell If nor arguments are given sh will start up the shell specified by the SHELL environment variable or bin sh if the SHELL environment variable is not set For example gt sh ls will execute the 1s command in the current working directory Diagnostics The inferior shell when sh is invoked with arguments is sh not csh so certain csh features will not work in particular the for pathnames 40 show show Purpose Show SIMLAB parameters and values Synopsis show mode param Description The show command displays SIMLAB parameters and values With an arg
21. ain area for elements m 0 0 ass area of the fet source sidewall m 0 0 asd area of the fet drain m 0 0 nrs number of squares source res calc 0 0 nrd number of squares source res calc 0 0 vto zero bias threshold voltage V 0 1 0 kp transconductance parameter AV 0 10u gamma bulk threshold parameter vi 0 0 37 phi surface potential Vv 0 0 65 cgso G S overlap cap m of width Fm 0 40p cgdo G D overlap cap m of width Fm 0 40p cgbo G B overlap cap m of length Fm 0 0 2n tox oxide thickness m 10u 10u nsub substrate doping ernie 0 4 0e15 nfs fast surface state density cm7 0 10G xj metallurgical junction depth m 0 lu ld lateral diffusion m 0 0 8u uo surface mobility cm Vs 1 600 700 vmax maximum drift velocity ms 0 50K delta width effect on thres 0 1 hold voltage theta mobility modulation 0 0 1 eta static feedback 0 1 kappa staturation field factor 0 2 0 5 fe coefficient for forward 0 2 1 2 bias delp cap formula js bulk junc sat current Am 0 if per m of area mj bulk junction bottom grad Fm 0 5 0 2m coefficient mjsw bulk junction sidewall grad Fm 0 5 0 2m coefficient Table 4 Level 3 MOSFET model parameters 22 name parameter units defaults examples j zero bias junc bottom capacitance m of area zero bias junc sidewall capacitance m of area bulk junc potential source resistance per square drain resistance per square surface state density bulk junc sat current Table
22. am and DARPA contract N00014 87 K 825 Miguel Silveira was partially sup ported by the Portuguese INVOTAN committee and Andrew Lumsdaine was also supported by an AEA Dynatech faculty development fellowship Installing SIMLAB in your computer system is done with the aid of makelinks a tool for avoiding code duplication developed at MIT by G Adams D Siegel and S Narasimhan The program uses a circuit parser written by P Moore and a sparse matrix solver based on work by K Kundert both of whom were students in computer aided design at U C Berkeley The front end interpreter for the program was inspired by the xlisp program written by David Michael Betz and uses the readline library from the Free Software Foundation s bash program The plotting package included with the SIMLAB distribution is xgraph a two dimensional plotting pack age developed by D Harrison at U C Berkeley Section 3 of this user s manual was derived in part from R Saleh s and A R Newton s SPLICE User s Manual available from U C Berkeley Question or problems related to the installation or usage of the SIMLAB circuit simula tor should be addressed to any one of the authors by U S mail or by electronic mail to simlab rle vlsi mit edu 18 62 0 214 Any bugs should be reported by electronic mail to simlab bug rle vlsi mit edu so that they can be solved for later releases Further more the authors welcome any comments suggestions or enhancements that will come
23. ared cgs Preconditioned Conjugate Gradient peg 53 e Preconditioned Conjugate Gradient Squared pcg e Conjugate Gradient applied to the normal equations cgnr e Conjugate Gradient applied to the normal equations cgnr e Conjugate Residual cr e Generalized Conjugate Residual gcr e Preconditioned Generalized Conjugate Residual pgcr e Preconditioned Restarted Generalized Conjugate Residual pgcr k e Orthomin orthomin These algorithms can be specified as linear system solvers see Functional Controls in sectionB 3 and are added to the list of possible values for the solve_linear parameter for both DC and Transient modes whenever this package is linked into SIMLAB The addition of this package and further setting up the solve_linear parameter to use one of the functions provided therein leads to the installation of some extra variables Normally one can expect that a bound on the number of iterations allowed for the iterative method will be one such variable Usually it is named after the algorithm being used for instance maxcg Increasing maxcg may cause an otherwise non converging method to suddenly converge At present each mode of simulation will have its own associated variable whose name for DC simulation will be such as maxdccg Using the who command will allow you to determine which new variables were added to your environment when one of the new algorithms is chosen for linear system solution If an iterative algori
24. cceptable See Appendix B for a complete description of SIMLAB s variables and the rules that guide their usage and the changes in their values 2 1 1 Command Line Editing One handy feature of SIMLAB in interactive mode is its command line editor which is implemented with the readline library of the Free Software Foundation s bash program The default key bindings are essentially patterned after gnu emacs or tcsh and allow the user to recall and edit previous lines Table 1 shows the most primary key bindings for the SIMLAB command line editor For more information about readline refer to the bash documentation from the Free Software Foundation The command line editor saves each line that is entered into a history list The history list can be accessed via the C n and C p keys down and up history respectively The entire history list can be displayed with the history command The run time length of the history list is controlled by the SIMLAB variable histlength Upon exiting SIMLAB saves the history list on a file The size of the saved history list is controlled by the SIMLAB variable savehist and cannot exceed the value of histlength By default upon starting SIMLAB looks for the environment variable SIMLAB_HISTFILE for the location of the history file If this variable is not set SIMLAB will use the default location which is defined at compile time normally simlab hist see config h if you desire to change this value
25. ductance to ground at each node e nrvabs nrvrel Newton Raphson absolute and relative voltage convergence criteria e nrcabs nrcrel Newton Raphson absolute and relative current convergence criteria e lterel lteabs absolute and relative local truncation error e nralpha Newton Raphson AV step limit e newjacob Number of Newton iterations before updating the Jacobian maxtrnr maxdcnr Maximum number of transient and dc Newton Raphson iterations allowed dode dotran flags indicating de or transient solution is desired verbose flag indicating verbose mode e simdebug flag indicating debug mode Simulation statistics are also reported for all phases of the simulation process In the bibliography references to standard textbooks and papers on circuit simulation and related topics are given In its basic form SIMLAB is a powerful circuit simulator but it is also designed to be easily customized for research purposes For example SIMLAB forms the core of special purpose simulation programs such as a switched capacitor filter simulator and a simulator for vision circuits The program code is highly modular so that researchers can easily construct and test algorithms by inserting them into the existing SIMLAB framework For information on how to add algorithms to SIMLAB see The SIMLAB Programmer s Guide The SIMLAB program was developed at MIT under support from Analog Devices the NSF PYI progr
26. e what Other options include increasing the value of cmin reducing the absolute and relative convergence criteria or increasing the maximum number of iterations on iterative solvers 10 3 The Circuit File Although the user interacts with SIMLAB in batch or interactive mode circuits are read from circuit description files specified with the circuit command A circuit description file contains element models circuit elements subcircuit definitions and selected simulation parameters Example circuit files can be found in Appendix F 3 1 Fundamentals 3 1 1 Models and Elements The following elements can be used to construct circuits for SIMLAB linear resistors lin ear capacitors diodes voltage controlled current sources bipolar and MOS transistors The BJT transistor model in SIMLAB is an adaption of the integral charge control model of Gummel and Pool with extensions that include several effects of high bias levels For a more detailed description see 8 The MOS transistors in SIMLAB are modeled by the Schichmann Hodges equations 7 SPICE2 level 1 or by those of the semi empirical model described in 8 SPICE2 level 3 SIMLAB also supports the following types of indepen dent sources constant current sources constant grounded voltage sources piecewise linear time dependent grounded voltage sources and sinusoidal time dependent grounded voltage sources Floating voltage sources are not yet supported The model statement
27. e plot line in the circuit file will be plotted individual nodes cannot be selected from that list This should change in a future release printenv printenv Purpose Print the value of an environment variable Synopsis printenv env _var Description printenv prints out the values of the variables in the UNIX environment of the SIMLAB process If a variable is specified only its value is printed 37 quit quit Purpose Leave SIMLAB Synopsis quit Description The quit command terminates the current SIMLAB session Any open diary file is closed run run Purpose Perform a simulation Synopsis run Description The run command begins a simulation run If the dodc variable is set TRUE a DC solution is initially attempted If the dotran variable is set a transient simulation is attempted Transient simulations started with run begin at time t 0 and end at time t stop The user can stop a simulation in progress by typing ctrl c 38 set set Purpose Set simulation parameter Synopsis set mode param val Description The set command assigns value val to parameter param in mode mode If no mode is specified the parameter is assigned value val irrespective of the simulation mode val must be a valid value for param See Section B for a description of available parameters and values setenv setenv Purpose Set environment variable
28. efine inverter input output ml output input 0 0 pulldn w 10u l 5u m2 vdd output output 0 pullup w du l 10u end inverter and then a circuit that is a string of inverters could be described by inverter inl outl inverter inverter outl out inverter inverter out out inverter Node names are not the only parameters that can be passed into subcircuits It is also possible to pass number parameters to subcircuits For example if one wanted to scale the width of the above inverter keeping the same width length ratios the inverter subcircuit could be defined as follows define inverter input output parameters w 10u ml output input 0 0 pulldn w w l 0 5 w m2 vdd output output 0 pullup w w l 2 0 w end inverter and then a circuit that is a string of inverters could be described by inverter inl outl inverter inverter out out invertsr w 20u inverter out out inverter w 400u 12 where inverterl would be assigned the default value of 10 microns for the width 3 1 3 Locals and Globals It is possible to have local nodes in a subcircuit In fact if any node name that is not contained in the node list of the define statement for the subcircuit is used in the subcircuit it will automatically be local to the subcircuit This can be overridden by explicitly declaring certain nodes to be global using the global statement This is particularly useful for supply voltage node names Note however that the first n
29. ered If a quit command is not given in the configuration file SIMLAB will enter interactive mode after reading it and executing any commands therein unless the command line argument q is given in which case SIMLAB exits after executing the command contained in the configuration file In general an interactive simulation session will proceed as follows 1 Start SIMLAB perhaps with a circuit file configuration file or both 2 Configure the simulation environment interactively with a configuration file or both 3 Run simulation 4 Plot simulation results 5 If not done change circuit parameters and go to 2 When SIMLAB is first started it attempts to read a startup file SIMLAB first looks for the file specified by the environment variable SIMLAB_RC If this variable is not set SIMLAB tries to read in order simlabrc and simlabrc 2 1 The SIMLAB Front End The primary interface to SIMLAB is through an interpretive front end The front end reads commands and expressions either interactively or from a configuration file and evaluates them See Appendix A for a description of the available SIMLAB commands SIMLAB will also evaluate expressions For example typing in gt a 5 pi will produce the result a 15 708 Notice that the variable a has been created and now exists in the SIMLAB environment If you now type gt a SIMLAB will return the value of a a 15 708 SIMLAB has predefined
30. floating voltage sources 3 5 9 Piecewise linear Voltage Sources Piecewise linear Voltage Sources Element Definition name nodel node2 pwl delay value period value t0 value v0 value 124 value v24 value Example vin 1 0 pwl delay 0ns period 100ns t0 0ns v0 5 0v t1 10ns v1 5 0v t2 15ns v2 0 0v t3 95ns v3 0ns Nodel is the positive node of the voltage source and node must be the ground node SIMLAB does not yet support floating voltage sources There are three types of parameters for the pwl There can be up to 20 0 through 19 breakpoints in the piecewise linear waveform which are pairs ti sec vi volts There is also a delay parameter which causes each breakpoint is delayed by the amount specified Finally there is the period parameter which when specified causes the waveform to repeat after the given number of seconds 28 3 5 10 Sinusoidal Voltage Sources Sinusoidal Voltage Sources Element Definition element name nodel node2 sine phase value freq value ampl value offset value Example vin 1 0 sin ampl 1v freq 1k Nodel is the positive node of the voltage source and node2 must be the ground node SIMLAB does not yet support floating voltage sources 3 6 Analysis and Control Statements 3 6 1 Plot Statement The only way to specify desired output from a SIMLAB simulation is with the plot statement and theref
31. formation on how to add algorithms to SIMLAB see The SIMLAB Programmer s Guide LICENSE AGREEMENT SIMLAB copyright C 1989 1990 1991 by Andrew Lumsdaine L Miguel Silveira Jacob K White and Massachusetts Institute of Technology Cambridge MA All rights reserved This Agreement gives you the LICENSEE certain rights and obligations By using the software you indicate that you have read understood and will comply with the terms Permission to use copy and modify for internal noncommercial purposes is hereby granted Any distribution of this program or any part thereof is strictly prohibited without prior written consent of M I T Title to copyright to this software and to any associated documentation shall at all times remain with M I T and LICENSEE agrees to preserve same LICENSEE agrees not to make any copies except for LICENSEE S internal noncommercial use or to use separately any portion of this software without prior written consent of M I T LICENSEE agrees to place the appropriate copyright notice on any such copies Nothing in this Agreement shall be construed as conferring rights to use in advertising publicity or otherwise any trademark or the name of Massachusetts Institute of Technol ogy or M LT MILT MAKES NO REPRESENTATIONS OR WARRANTIES EXPRESS OR IM PLIED By way of example but not limitation M I T MAKES NO REPRESENTATIONS OR WARRANTIES OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR
32. from other users experience with the program 2 A SIMLAB Primer SIMLAB is invoked from the command line as follows simlab c circuit_file r f diary_file qvV config_file SIMLAB can be used in interactive mode in batch mode or both The command line arguments are c circuit specifies a circuit file to be read initially See the circuit command in Section A f diary file specifies a diary file to be used initially See the diary command in Section A r specifies that a run is to be executed using the known data This option requires that a circuit file be specified and tells simlab to use the default methods to simulate the given circuit q turns off interactive mode When this command line argument is given SIMLAB will exit after executing the command contained in the specified configuration file If no configuration file is given this line argument is ignored v turns on verbose mode in which case SIMLAB emits certain diagnostic messages See the description of the verbose environment variable in Section B V turns on debug mode in which case SIMLAB emits many diagnostic messages See the description of the simdebug environment variable in Section B config file is an initial configuration file read by SIMLAB If a circuit file is also specified the configuration file is read after the circuit file SIMLAB will read and execute each line of the configuration file just as if the commands were interactively ent
33. h node Should not be set to zero Default lp mhos histlength Description Size of the history list to be kept by SIMLAB at run time Default 100 Description Absolute local truncation error tolerance Default 5m Description Relative local truncation error tolerance Default 10m 45 maxdcnr Description Maximum number of newton iterations in the dc simulation to be attempted before indicating failure Default 200 Description Maximum number of newton iterations in the transient simulation to be attempted before indicating failure Default 10 maxsteps Description The simulation interval divided by maxsteps yields the smallest allowable timestep Default 1 0e8 minsteps Description Minimum allowable number of steps in simulation interval Default 50 newjacob Description Number of newton iterations used before re evaluating Jacobian Default 3 46 Description Maximum allowable voltage step in Newton iteration update Default 0 3 nrcabs Description Absolute Newton current error tolerance Default In nrcrel Description Relative Newton current error tolerance Default 1m nrvabs Description Absolute Newton voltage error tolerance Default 1m nrvrel Description Relative Newton voltage error tolerance Default lm 47 Description Si
34. he elements defined within the 16 subcircuit are inserted into the circuit The node names specified in the element statement are substituted for the node names in the subcircuit definition statement This substitution is by order the first node in the element statement is substituted for the first node in the subcircuit definition and so on Note that the node names in the subcircuit definition must be enclosed in parentheses and that it is an error for the element statement to have a different number of nodes than the subcircuit definition it refers to Any nodes used within the subcircuit which are not global contained on the global node list and are not listed in the subcircuit definition statement are local to that subcircuit ie these names are not known outside the subcircuit definition Since a global node cannot be replaced during a subcircuit expansion it is an error for a global name to appear as a node on a subcircuit definition statement The subcircuit can optionally include a parameters statement To specify subcircuit pa rameters the keyword parameters is followed by a list of parameter names and default values separated by equals A named parameter can be used as if it were a number in the subcircuit description and in addition can be multiplied by a floating point number scale factor An element statement which refers to the subcircuit can set the values of any or all of the names parameters Any parameters tha
35. junction sidewall cap per meter of junction perimeter bulk junction potential lateral diffusion bulk junction saturation current zero bias B D junc cap zero bias B S junc cap Table 2 Schichmann Hodges MOSFET model parameters 20 name parameter units examples w channel width m 1 channel length m as area of source region m ad area of drain region m perimeter of source region m perimeter of drain region m Table 3 Schichmann Hodges MOSFET element parameters Bipolar Transistor Models BJT Model Definition model model name model type parameter list BJT Element Definitions name collector base emitter substrate model name params Examples model nbjt npn bf 200 vaf 250 tr 10n model pbjt pnp load1 vdd 3 5 0 nbjt pulldn 1 output outbar 0 0 pbjt bf 100 The model parameters used in SIMLAB BJT model are as given in Table 7 Any parameter not specified will be set to its default value The element parameters are listed in Table 9 3 5 3 Diodes Diodes Model Definition model name d parameters Element Definition element name anode cathode model name area value Example model pnj d cj0 8e 12 di drain pnj area 2p d2 0 source pnj area 2p 21 parameter defaults examples w default width for elements m 1 l default length for elements m 1 2u as default source area for elements m 0 0 ad default dr
36. l refresh C n down history C p up history C q quoted insert C r isearch backward C s isearch forward C t transpose chars C u universal argument C w kill region C y yank SPC self insert command ESC 0 ESC 9 digit argument ESC b backward word ESC c capitalize word ESC d kill word ESC f forward word ESC g goto line ESC 1 downcase word ESC t transpose words ESC u upcase word ESC y yank pop ESC list completions ESC DEL backward kill word Table 1 sIMLAB Key Bindings integrate Specifies which integration method to use simulate Specifies what type of simulation structure to use environment Specifies the environment in which SIMLAB is being used This will normally be serial but functionality to take advantage of parallel computer architectures can be added Furthermore with the notion of simulation mode some of the above functional controls can be given different meanings depending on the current mode of simulation Section B contains a detailed description of these functional controls The functional controls are modified with the set command and displayed with the show command see Appendix A For example if you are testing out a new linear system solver called baz and have properly compiled it into SIMLAB see the SIMLAB Programmer s Guide you would set the transient linear system solver to baz with gt set trans solve_linear baz Or if baz was a more generic function you c
37. nction with a sophisticated and versatile simulation engine The program is specifically designed to be used as an educational tool and as a research platform SIMLAB can be operated in either batch or interactive mode The user is allowed to separately specify algorithms for the various aspects of the simulation These include e Simulation environment e g serial or parallel depending on the underlying hardware e ODE system solution e g point e ODE system time integration e g backward Euler trapezoidal second order Gear e Nonlinear algebraic system solution e g multidimensional Newton s method nonlin ear relaxation e Linear system solution e g sparse Gaussian elimination Gauss Jacobi relaxation conjugate gradient conjugate gradient squared Furthermore SIMLAB has a notion of simulation mode and different methods can be specified for different modes At present supported modes are DC for the calculation of operating points and Transient for the calculation of the time response of a circuit For instance assuming that the user has specified the multidimensional Newton s method for solving the nonlinear system of equations the linear solver associated could be different depending of what type of simulation is being performed The user can also interactively tune the following simulation parameters e stop final simulation time e cmin minimum capacitance to ground at each node e gmin minimum con
38. nition model name r r value Element Definition element name nodel node2 model name or r r Example model rmod r r 15k rl input gate rmod r2 1 2 r r 10k Nodel and node2 are the nodes to which the resistor is connected Value is the resistance in ohms and must not be set to zero 26 3 5 5 Capacitors Capacitors Model Definition model name c c value Element Definition element name nodel node2 model name or e ce value Examples model cmod c c 5uf cl input gate cmod c212cc 15P Nodel and node2 are the nodes to which the capacitor is connected Value is the capacitance in farads 3 5 6 Constant Current Source Constant Current Source Element Definition element name nodel node2 i i value Example biasl 1 2 ii 20ua The current value in amperes flows from nodel to node2 3 5 7 Voltage Controlled Current Source Voltage Controlled Current Source Element Definition element name nodel node2 node3 node4 vecs gm value Example vecsl 1 2 3 4 vecs gm 3 The current value x v3 v4 flows from nodel to node2 27 3 5 8 Constant Voltage Sources Constant Voltage Sources Element Definition element name nodel node2 de v value Example vec 1 0 de v 5 0v Nodel is the positive node of the voltage source and node2 must be the ground node SIMLAB does not yet support
39. ns First Order MOS Model and Element Definitions MOS Model Definition model model name model type parameter list MOS Element Definitions name drain gate source bulk model name params Examples model pullup nmos vto 5 2 gamma 0 914 kp 69u phi 0 6 lambda 0 02 model pulldn pmos vto 1 12 gamma 0 266 kp 79u phi 0 6 lambda 0 02 load vdd output output 0 pullup w 5u 1 20u pulldn 1 output outbar 0 0 pulldn w 10u 1 5u 18 The model parameters used in SIMLAB Schichmann Hodges MOSFET model are as given in Table 2 Any parameter not specified will be set to its default value The element parameters are listed in Table 3 MOS Level 3 Model and Element Definitions The MOS level 3 model is based on the model available in the SPICE2 program 6 although numerous modifications have been made to enhance the speed and insure the accuracy of the model This model is suitable for small geometry MOSFETs and it accounts for second order effects such as threshold voltage sensitivity to the length and width of the device and lowered saturation voltage and current due to velocity saturation The details of this model may be found in 8 MOS Level 3 Model and Element Definitions MOS Model Definition model model name model type parameter list MOS Element Definitions name drain gate source bulk model name params Examples model pullup nmos3 vto 5 2 gamma 0 914 kp 69u phi 0
40. ns A number field may be replaced by an integer i e 12 44 a floating point number 3 14159 or an integer or floating point number followed by an integer exponent 1E 14 2 65e3 Scale factors An integer or a floating point number can be scaled if followed by one of these scale factors g 1E9 meg 1E6 k 1E3 m 1E 3 u 1E 6 n 1E9 p 1E 12 f 1E 15 14 Letters immediately following a number that are not scale factors are ignored and letters immediately following a scale factor are ignored Hence 10 10v 10volts and 10Hz all represent the same number and m ma msec and mmhos all represent the same scale factor Note that 1000 1000 0 1000Hz 1E3 1 0E3 1kHz and Ik all represent the same number 3 3 Choosing Node Names Node names A node name can have any number of letters or numbers in it and must not contain any delimiters only alphanumeric characters If the node name is not all numbers it must start with a letter For example a7 or 7 are acceptable names but 7a is not Ground Node and Global nodes Global names can be used whenever you want to de fine a node name that is to be used in the main circuit as well as subcircuits They are generally used for supply voltage names Any number of global nodes can be specified using the global statement Its format is the keyword global followed by a list of node names The global statement also performs another function that of indicating to the SIMLAB program which node to use
41. o in each pair connected by an equal sign For example 13 forces the initial condition for node input to be 5 volts Finally the user can request that SIMLAB perform an explicit dc solution as available in SPICE2 and begin the transient analysis with that solution The nodes that have been specified by an ic statement are forced to their respective values for the dc solution 3 1 6 Comments Any line in the circuit description file that begins with a semicolon is assumed to be a comment line and is ignored 3 2 Basic Language Rules Field separators Delimiters may be one of more blanks or a comma These delimiters must be placed where required by the syntax of the circuit description language Continuation Character A statement may be continued by ending it with a backslash and continuing on the next line Name Field A name field can have any number letters or numbers in it and must not contain any delimiters only alphanumeric characters In all cases the name must start with a letter For example alu or fadder7 are acceptable names but 7alu is not Lower and Upper Case All keywords ic plot define model end parameters global must be in lower case Otherwise no distinction is made between upper and lower case letters the names signalOne and SignalOne are considered to be identical by SIMLAB Case may be used for ease of comprehension however provided it is used with care Number representatio
42. ode specified on the global list is always the ground or reference node 3 1 4 Control Statements Information such as the simulation period the simulation accuracy criteria and analysis requests are specified with a single options statement as follows simlab options stop 100ns dodc 1 dotran 1 Default values are used whenever parameter values are not set explicitly by the user The value of stop should always be set by the user as it sets the simulation interval In order to request that the output of certain nodes in the circuit are recorded the plot statement is used and its format is just the keyword plot followed by a list of node names A warning will be issued if the input file does not specify any nodes for plotting 3 1 5 Initial Conditions and the DC Solution The SIMLAB program allows the user two ways of specifying the initial conditions used to begin a transient analysis The default is that all the node voltages begin at zero This can be thought of as a power up phase However the implication of this strategy is that the circuit should not be clocked until it has settled after powering up If the circuit is clocked too early the simulation will still be performed without error but the circuit may not behave as expected If desired it is possible to force a node to be initialized to any voltage by using the ic statement Its format is the keyword ic followed by a list of node name initial value pairs with the tw
43. ore every circuit description file should have this statement All the nodes to be plotted must be listed after the plot keyword and this keyword should appear only once in a circuit description file There is no limit to the number of plotted nodes but it is an error to try to plot an unused node In the third example above latch and latch2 are two subcircuit instances with the internal node store Plot Statement General Form plot nodel node2 node N Examples plot clock j k q qbar plot phasel phase2 latch1 store latch2 store For each node name following the plot keyword SIMEAB will produce an entry in the output file with the node name time and voltage The file will have the same name as the circuit file except with a trans extension The plot file contains a collection of time voltage pairs This format was chosen because it allows the end user to write a post processor to fit a given terminal with the minimum of effort in fact the plot command available from the front end spawns a post processor to read the plot file Note that if accuracy is critical the points should be interpolated with a 2 order Lagrange polynomial However linearly 29 interpolating the points is in most cases good enough and produces reasonably good plots 3 6 2 Initial Conditions The ic statement forces the specified node to the given value for the calculation of the DC solution after which the node is allowed to take on
44. ough users of circuit simulators often don t include these capacitances Therefore the SIMLAB program will insert a minimum capacitance to ground at every node in the circuit This value of the minimum capacitance is set by the parameter cmin and is a user alterable but should not be set to zero Finally the SIMLAB program was developed at MIT as a research project It is not intended to be a production system although serious effort has been made to insure the correctness of the program it works for at least one test case Reporting problems to the authors about SIMLAB would be appreciated provided it is done gently 2 4 Hints on Convergence Obtaining the DC solution can be a difficult problem although SIMLAB seems to do a good job of it However there are still examples which will not work If you have trouble try playing with the options gmin and nralpha gmin is a conductance placed to ground at each node so it should be kept to a reasonable small value or your DC solution will not be accurate nralpha controls the maximum step a voltage can take in any one iteration of the DC solution SIMLAB does a very good job of converging during the transient solution In fact noncon vergence during the transient solution usually means that there is an error in the circuit or a bug in the program If you have problems during the transient solution it may help to set the option newjacob equal to 1 although this may slow the program down som
45. ould set it to be the linear solver for all modes of simulation namely DC and transient with gt set solve_linear baz You can examine the settings of the functional controls with show Typing gt show solve_linear will return the current settings for solve_linear for all known modes of simulation Just typing gt show will return the current settings for all functional controls and simulation modes If a functional control is set to a non existent function SIMLAB will output a warning and dismiss the change However if a change is made to a functional control such that the new value is incompatible with the current values of other functional controls SIMLAB will output an error message at run time For instance suppose that a new simulation method called simfoo is compiled into SIMLAB and is such that simfoo uses different data structures and therefore requires an integration method called simfooint If the user merely specifies gt set simulate simfoo and then request a run gt run SIMLAB will try to use the default integration algorithm and will output an error saying that that algorithm is not a valid setting for the current simulation control 2 3 Warnings about the Algorithms used in the SIMLAB Program One limitation of some popular simulation methods is that they sometimes do not converge unless there is a capacitor to ground at every node in the circuit This is a mild assumption for most realistic circuits alth
46. p ERL M80 7 Electronics Research Laboratory Report University of California Berkeley Berkeley California June 1980 63 64
47. t are not set on the element statement will be given its default value The most recently begun subcircuit is terminated by the end statement An optional name may be specified after the end statement to indicate which subcircuit definition is being completed This name is not used by the program but is useful to include for readability Internal subcircuit nodes may be referenced for plotting or for assigning initial conditions by using a name derived from its subcircuit node name and the subcircuit instance name separated by a dot For example adder1 i1 refers to internal node il in a subcircuit instance called adder1 17 Subcircuit Definitions General Form define subcircuit name node 1 node N parameters paraml default paramN default element statements end subcircuit name Example define invert output input parameters w 5u m1 vdd output output 0 depload w w 1 1 0 w m2 output input 0 0 pulldn w 5 0 w l w end invert 3 5 Electrical Elements 3 5 1 MOS Models There are two MOSFET models that can be used to simulate circuits with the SIMLAB program There is a first order model based on the Schichmann Hodges equations 4 for the dc drain current and a more complicated one whose equations are the same as for SPICE2 MOS Level 3 An MOS model may be either N channel or P channel enhancement or depletion First Order MOS Model and Element Definitio
48. ters model tran nmos vto 1 kp 20u gamma 0 31 phi 0 6 lambda 0 02 Voltage sources vsrc vdd 0 de v 5 input in O pwl period 50ns t0 0n vO 0 ti 15ns vi 0 t2 20ns v2 5v t3 40ns v3 5v t4 45ns v4 5v Transistors moi vdd boot out O tran w 5u 1 5u mo2 vdd vdd boot O tran w 5u 1 5u mo3 out in O O tran w 5u 1 5u Capacitors c1 boot O c c 0 001pf c2 out 0 c c 0 01pf c3 boot out c c 0 01pf Analysis options Do not do DC solution Do Transient analysis for 125ns simlab options dodc O stop 125ns cmin 1 e 14 lterel 0 0005 lteabs 0 000005 Record the voltages of the following nodes plot in out boot 58 A CMOS Domino Gate with complex models is given below domino rel domino CMOS circuit Required global statement First in list indicates ground node global 0 Record the voltages of the following nodes plot 123456789 10 Analysis options simlab options stop 100ns dodc 1 Input Sources vdd 100 O de v 5 vphi 10 O pwl period 40ns t0 0 vO 5 ti ins vi 0 t2 16ns v2 0 t3 17ns v3 5 vala3 1 0 pwl period 40ns t0 0 v0 5 ti 2ns vi 5 t2 3ns v2 0 t3 18ns v3 0 t4 19ns v4 5 va2a4 2 0 pwl t0 0 vO 5 ti 2ns vi 5 t2 3ns v2 0 t3 100ns v3 0 va5 9 0 pwl period 40ns t0 0 vO 5 ti 2ns vi 5 t2 3ns v2 0 t3 18ns v3 0 t4 i9ns v4 5 Devices mpphi 4 10 100 O pqshare w 7u 1 3u ad 56p as 56p pd 30u ps 30u mai 3 1 7 O nqshare w 7u 1 3u ad 10 5p as 10 5p pd
49. thm is chosen along with a preconditioner for inproved convergence rate a parameter called precondition is added to your environment At present this package supports the following types of preconditioners e Identity preconditioner none e Diagonal Preconditioner diag e Incomplete Choleski preconditioner ic e Incomplete Choleski preconditioner mic Incomplete LU preconditioner i1 e Incomplete LU preconditioner with Markowitz ordering mil For information on the algorithms available in this package we refer the user to the appro priate documentation such as 2 1 54 D Example Configuration File bootinv cfg SIMLAB Boot strapped inverter example Configuration file h Save output in diary file diary boot doc Change to circuits directory cd circuits Load circuit circuit boot rel Y Make sure to do DC solution dodc 1 Use direct methods for linear solution set solve linear direct Use 2nd order backwards differentiation integration formula set integrate gear2 Run run Plot the results on the display plot Done diary off quit 55 E Example Session Example Simlab Session lt SIMLAB 1 0 gt c 1990 Massachusetts Institute of Technology Research Laboratory of Electronics All Rights Reserved 10 Oct 90 gt 4 Change to circuits directory gt cd circuits gt Load circuit gt circuit boot
50. uit boot rel tion thod N lution lution Time tution Meth He Solution Metk iE n Iteratio Kd 5 lution M Initial Decc tian Tim Linea lution Time a a 40 00 60 00 pie Figure 1 Screen Dump of a SIMLAB session for circuit boot rel G Example SIMLAB Session En 61 Tdi 62 References 1 G H GOLUB AND C F Van Loan Matriz Computations The John Hopkins Uni versity Press Baltimore Maryland 1983 2 M R HESTENES AND E STIEFEL Methods of conjugate gradients for solving linear systems Journal of Research of the National Bureau of Standards 49 1952 pp 409 436 3 W D HiLLis The Connection Machine MIT Press New Haven CT 1985 4 A LuMSDAINE M SILVEIRA AND J WHITE CMVSIM programmer s guide Research Laboratory of Electronics Massachusetts Institute of Technology Unpublished 1990 5 CMVSIM users guide Research Laboratory of Electronics Massachusetts Insti tute of Technology 1990 6 L W NAGEL SPICE2 A computer program to simulate semiconductor circuits Tech Rep ERL M520 Electronics Research Laboratory Report University of California Berkeley Berkeley California May 1975 7 H SCHICHMANN AND D A Hopaes Modeling and simulation of MOS insulated gate field effect transistor switching circuits IEEE Journal Solid State Circuits SC 3 1968 pp 285 289 8 A VLADIMIRESCU AND S Liu The simulation of MOS integrated circuits using SPICE2 Tech Re
51. ument show displays the specified parameter and values for the various modes If a mode is also specified along with a parameter then only the value of that parameter for the mode in question is shown Without an argument show displays all the parameters and their values for the various modes See Section B for a description of available parameters and values source source Purpose Load and execute a SIMLAB configuration file Synopsis source filename Description The source command causes SIMLAB to read and execute a SIMLAB configuration file Diagnostics SIMLAB attempts to interpret everything in the specified file Funny things can happen if it is given a file which is not a SIMLAB script 41 unsetenv unsetenv Purpose Unset environment variable Synopsis unsetenv env_var Description unsetenv removes the variable env_var from the UNIX environment who who Purpose Display variables existing in the SIMLAB environment Synopsis who Description The who command displays the variables existing in the SIMLAB environment The variables are grouped into three categories system constants application variables and user defined variables See Section B for a description of SIMLAB environment variables 42 B SIMLAB Variables B 1 System Constants Description Boolean value True Can be used with boolean simulation variables e g dodc True True is equivalent to integer value one
52. variables which correspond to certain simulation parameters that the user can set via the front end These variables include stop final simulation time e cmin minimum capacitance to ground at each node e gmin minimum conductance to ground at each node e nrvabs nrvrel Newton Raphson absolute and relative voltage convergence criteria nrcabs nrcrel Newton Raphson absolute and relative current convergence criteria e lterel lteabs absolute and relative local truncation error nralpha Newton Raphson AV step limit newjacob Number of Newton iterations before updating the Jacobian maxtrnr maxdcnr Maximum number of transient and de Newton Raphson iterations allowed e dodc dotran flags indicating dc or transient solution is desired e verbose flag indicating verbose mode e simdebug flag indicating debug mode See Appendix B for a complete description of these variables The values of these variables can be examined and changed in the obvious way For instance if you type gt cmin SIMLAB will return with the value of cmin e g cmin 1 e 15 To change the value of cmin to 1 0e 12 type in gt cmin 1 0e 12 SIMLAB will then reply cmin 1 e 12 The value of cmin used during simulation will now be 1 0e 12 Note that the predefined system variables can be used in algebraic expressions For example an input line like gt cmin stop 1 0e 6 is perfectly a
53. whatever value is determined by the circuit The DC solution uses zero for an initial guess for all nodes other than those specified by an ic statement or set by a voltage source Initial Conditions General Form ic nodel valuel node2 value2 node N value N Example ic a 5 0 b 0 2 c 0 3 d 5 0 3 6 3 Simulation Options The options statement is used to specify the analyses to be performed and the balues of simulation parameters to be used These options their defaults and an explanation of each is given in Table 11 With the exception of dodc dotran and stop these parameters should only be adjusted by an informed user The defaults should work well for most cases When an option is set from within a circuit file that value of the option will only apply for that simulation and until another circuit is read in When another circuit is read in all simulation options are first reset to their default values The new circuit may then possibly modify some of the options but those modifications would only apply to that particular circuit The default values of these options can be modified from the front end See Section B 2 for a more detailed explanation of the behavior of the simulation options Simulation Options General Form simlab options param1 valuel param N value N Examples simlab options stop 100ns dodc 0 simlab options stop 100ns cmin 1e 16 30 definition If equal to
54. with CMVSIM 5 4 the vision circuit simulator developed on the Connection Machine 3 Values dc serial sequential computer environment tran serial sequential computer environment Default dc serial tran serial B 4 Environment Variables SIMLAB PLOTTOOL Description Specifies which program to use for plotting node waveforms when the plot com mand is used This program must be in the user s PATH By default SIMLAB uses SIMGRAPH a modified version of the XGRAPH program SIMLAB PLOTARGS Description Contains command line arguments to be used when invoking SIMLAB_PLOTTOOL for plotting node waveforms It is disregarded if the default tool SIMGRAPH is used SIMLAB HISTFILE Description Specifies the location and name of the file to use as history file If not set SIMLAB will use the default naming specified at compilation time normally simlabhist 51 SIMLAB_RC Description Specifies the location and name of the default SIMLAB configuration file This file is read by SIMLAB at startup time If this variable is not set SIMLAB tries to read in order simlabrc and simlabrc 52 C Non Standard Supported Packages Currently SIMLAB supports two packages not included under what is called the standard functionality These are the Iterative Linear System Solution package and the Wave form Newton Circuit Simulation package
55. ze of the history list to be saved upon exiting SIMLAB Default 100 Description Flag indicating simdebug mode This is a debugging mode and a large amount of diagnostic messages are printed There should never be any reason to set simdebug to True Default False Description stop specifies the length of the transient simulation interval Transient simulations started with run begin at time 0 and end at time t stop Transient sim ulations started with continue begin at time t PresentTime and end at time t stop Default Is verbose Description Flag indicating verbose mode This is a debugging mode and a large amount of diagnostic messages are printed There should never be any reason to set verbose to True Default False 48 B 3 Functional Controls One of the most powerful features of SIMLAB is the ability to specify the algorithms to be used at different levels of the simulation for the various simulation modes This feature is most useful for the individual who is developing and testing new algorithms For most people using SIMLAB strictly as a circuit simulator the default functions will be good enough In this section the seven functional controls are described along with valid values for them solve_linear Description Specifies function to be used for linear system solution during simulation Different functions can be specified for DC and Transient simulation Values
Download Pdf Manuals
Related Search
RLE TR 588 319047 is31lt3948-grls2-tr