digital circuit simulation using hspice - Computer
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1. February 7 2001 DIGITAL CIRCUIT SIMULATION USING HSPICE Charles R Kime Dept of Electrical and Computer Engineering University of Wisconsin Madison The pdf version of this document has extensive hyperlinks shown in blue TABLE OF CONTENTS GETTING STARTED WITH HSPICE oenina 2 The HSPICE Netlist File cscs s2cccincartvncsines sass naos n eR E aR RREA 2 An Example HSPICE Fite soer eaaa aa ai 3 Executie PIS PIC carrura EA ues 4 Displaying HSPE PUU porpra E A ENEE EEE 6 Output Froti ein aE 6 HSPICE User s Manual and AvanWaves Help and Manual seesseseeeeesreerereen 7 HSFKLECOMMANDS css cssssesussnnsas teeth sua AEA EO AS ERA 7 INPUT WAVEFORM S ororena RORE E E RE onan RER REIRE 9 OUEPUT VARIABLE Surinin N 10 EXPRESSIN S uea E Canina aidierdioutiaasiean Mae pape es ona 10 SPECIFIC ANALYSES ANDOUTPU asa cecea seat cases anian knon sake danse PORNEA ERNEA 12 ey a E dei E nee T T A 12 Faly of EV CUYOS aneirin ee A ARE ERAR RERS 14 I V Curve for Parameter Extrae tioii roos niea 19 Voltage Transfer Characteristic VTO saiccssaascsevinrincreisinceanaaveanstastacwsabenieumabes 17 Transient Delay y ADAI RL Ss cice csSevoceacnssduacesandeees aan acssvnneaakssannivensauantanettnsetseianantanss 17 CONVERGENCE PROBLE MSsir n a a e A 19 DC AMAL YSIS avai cscsvicoeivciniennncneearneneun EE RR RERE RERE 19 Transient AYSE eo AEE 19 Diode Convergent snonririminn mna R TARR ERA 19 EXECUTING HSPICE FROM THE COMMAND LINE ssisesisccsscsessss2. aa I 800u 4a L Jp L H i 6001 4h E u Ji L dha F aa 400u SONS ae ie an ee eR ee 200u pal Cae See eee ee SE ee a E E pp ppp o 5n 10n 15n 20n 25n 30n 35n 40n 45n 50n 55n Time lin TIME Design Type Wave Symbol DO point usr5 k kime spices hspice examples nmos_inv Transient v 3 A DO point usr5 k kime spices hspice examples nmos_inv Transient v 4 DO point usr5 k kime spices hspice examples nmos_inv Transient power xX yena 18 DIGITAL CIRCUIT SIMULATION USING HSPICE DC Analysis Transient Analysis Diode Convergence CONVERGENCE PROBLEMS CONVERGENCE PROBLEMS Very infrequently one encounters some form of numerical convergence or other numer ical problem when using HSPICE Due to the low likelihood of these problems we give references only to the on line manual See page 5 5 and pages 5 8 through 5 26 of the on line manual See pages 6 6 through 6 19 of the on line manual Note that DC convergence problems can also affect convergence in transient analysis For handling of convergence for regular diodes see page 12 2 of the on line manual For handling of convergence for MOSFET diodes see page 15 19 EXECUTING HSPICE FROM A COMMAND LINE HSPICE places almost all of the output files from a run in the directory in the run direc tory i e the directory from which it is executed So you should change to the directory in which you would like the result files to appear Ex
3. node 4 is connected to the drain of M1 and to the gate and source of M2 Next NENH and NDEP give the name of the model for each of the transis tors The length L and width W of the channel of each device is given The abbreviation u designates micro which for length in the MKS system gives microns u In addi tion for transient analysis the areas of the drain of M1 and the source of M2 are given The abbreviation p designates pico which is Wr Line 12 specifies a capacitive load on the inverter output of 0 1 pf Line 15 includes the file nmos 3 containing the models DIGITAL CIRCUIT SIMULATION USING HSPICE 3 Executing HSPICE GETTING STARTED WITH HSPICE for the MOS transistors in this file Full path _to_spice_ model is the abso lute Unix path to the location where you place a copy of the spice model nmos 3 Note that your_name as a part of this path will not work The contents of this file appear later in this section The remaining lines specify analyses and outputs Line 18 performs a DC analysis that produces the voltage transfer characteristic for the circuit The voltage Vin sweeps from 0 volts to 5 volts in 0 1 volt increments Line 19 along with the word PROBE on line 26 specifies the output to be V 4 Line 21 performs a transient analysis that will permit the propagate delays rise and fall times and average power to be measured This command begins with TRAN and specifies an output every 0 1 ns for 60
4. 8E 10 10 CGDO 2 8E 10 CJ 5 75E 5 CJSW 2 48E 10 PB 0 7 MJ 0 5 Lf MJSW 0 3 NFS 1E10 12 Lines 2 through 6 and 8 through 12 describe the models for the enhancement mode and depletion mode transistors respectively Each model begins with MODEL followed by the name of the model the transistor type and the HSPICE model parameters for a Level 3 model Note the at the beginning of each subsequent line of the model param eter list The designates the continuation of a line Thus in HSPICE each model is a single statement HPSPICE places almost all of the output files from a run in the run directory i e the directory from which it is executed So you should change to the directory in which you DIGITAL CIRCUIT SIMULATION USING HSPICE Displaying HSPICE Output GETTING STARTED WITH HSPICE would like the result files to appear before executing AvanWaves or HSPICE If you are analyzing a new circuit design use your favorite editor to enter the initial version of design sp Then start AvanWaves by entering awaves To open a design click Design Open In the Open text area enter the design file path name if necessary Then select design sp and click OK If you have not run HSPICE on design sp you will get a message indicating that you should use Run HSPICE Next click Tools Run HSPICE The first time you use the Run Manager click on Preferences and select the editor you wish to use Depending on the editor you use you may
5. at least one input This command sets the number of columns to 80 for use with a terminal or 80 column output device INPUT WAVEFORMS PWL and PULSE are two input waveforms frequently used in transient analyses The format for a piece wise linear PWL waveform is PWL timeO valueO timel valuel time2 value2 where at timei the value of the waveform is set to valuei and remains there until value i 1 The value set at the last time remains until t oo For example Vin 3 0 PWL Ons OV 0 4ns 5V 14 6ns 5V 0 4ns OV starts Vin at 0 at t 0 ramps it to 5 volts by 0 4 ns and holds it there untilt 15ns It then ramps Vin down to 0 volts by t 15 4 ns and holds it as O volts thereafter The format for a PULSE waveform is PULSE intial value pulse value delay risetime falltime duration period The waveform begin at the intial_value The delay is the time from t 0 to the beginning of the pulse The risetime is the time required to go from the DIGITAL CIRCUIT SIMULATION USING HSPICE 9 OUTPUT VARIABLES intial value to the pulse value The falltime is the time to go from the pulse value to the intial_value The duration is the time that the pulse remains at the pulse value The period is the length of time from the end of delay to the rising edge of the next pulse For example Vin 3 0 PULSE 0 5 4 9n 0 2n 0 2n 4 8n 10n represents a pulse waveform that begins at 0 has a pulse beginning at t 5 ns measured at
6. file GLOBAL declares a variable to be the same whether in the main circuit or any subcir cuit For example GLOBAL Vdd will cause all nodes throughout the netlist file labeled Vdd to be connected together This avoids extra nodes in defining subcircuits DIGITAL CIRCUIT SIMULATION USING HSPICE 7 GRAPH INCLUDE LIB MEASURE MODEL OPTIONS PARAM HSPICE COMMANDS GRAPH can be used to plot output directly from HSPICE Plots from all GRAPH statements in a design sp file appear in a single postscript file Note that GRAPH is capable of handling a sweep of only one variable If a second variable is swept each of its values produces a separate plot The outputs of GRAPH are design gr where is an integer IC is useful for setting initial conditions for transient solutions This is essential in whenever the circuit stores information such as in latches flip flops or on dynamic storage nodes For example IC V 1 5 V 2 0 initializes node 1 to 5 V and node 2 to OV To use for initialization of a transient solution include UIC in the TRAN state ment A similar command useful for DC solutions is NODESET Used to include text from one file in another at run time For example INCLUDE pong usr5 k kime public_htm1 555 spice models scn0 hp L3 is used to include the text in the file scn06hp L3 for the level 3 models for the CMOS devices in an HP 0 6 u process Note that the abbreviate
7. line of the SPICE file contains the name of the circuit This line must always be present As in the second line all lines beginning with an asterisk are comments and are optional This file is more heavily commented than usual Lines 4 and 5 specify power supplies which are independent voltage sources A voltage source identifier always begins with V or v In order to interconnect components nodes represented by integers are used For example Vdd is connected with its terminal on node 1 and its terminal on node 0 Note that 0 is always used as the ground node Vdd is identified as a DC source with value 5V The and V are optional This circuit is somewhat unusual in that it has a substrate bias voltage Vbb 0 to give different cir cuit characteristics Vin in lines 7 and 8 is the input voltage to the circuit for transient analyses Two alter native specifications PWL Piece Wise Linear and PULSE are given The PWL speci fication begins with it is commented out and thus is not used although these two specifications are identical for the first 30 ns PULSE is useful for simple periodic wave forms such as clocks and PWL is useful for non periodic waveforms See the on line SPICE manual for the format of these waveform specifications Lines 10 and 11 describe the two MOSFETs in the inverter The use of M as the identi fier designates a MOSFET The order of the nodes is drain D gate G source S and substrate B For example
8. ns Line 23 along with the word PROBE in line 26 specifies that the only outputs are to be the voltages on nodes 3 and 4 which correspond to the input and output of the inverter Otherwise HSPICE outputs all voltages plus the power supply currents Line 25 uses MEAS which is the same as MEASURE to find a scalar value for the average power over a single full period of the Vin waveform The key word POWER causes the instantaneous power dissipated by the circuit as a function of time to be cal culated The measurement function AVG average then takes the average of POWER over the time interval specified by FROM and TO and assigns the value to the output vari able avgpow In general PROBE in a OPTIONS statement as on line 26 restricts the outputs to those specified in PROBE PRINT PLOT and GRAPH statements POST in OPTIONS causes the output files to be prepared for AvanWaves Finally END designates the end of the SPICE file The model file nmos 3 follows Model for Enhancement Mode MOSFET 1 MODEL NENH NMOS LEVEL 3 RSH 0 TOX 300E 10 LD 0 21E 6 2 XJ 0 3E 6 VMAX 15E4 ETA 0 18 GAMMA 0 4 KAPPA 0 5 3 NSUB 35E14 UO 700 THETA 0 095 VTO 0 781 CGSO 2 8E 10 4 CGDO 2 8E 10 CJ 5 75E 5 CJSW 2 48E 10 PB 0 7 MJ 0 5 5 MJSW 0 3 NFS 1E10 6 Model for Depletion Mode MOSFET 7 MODEL NDEP NMOS LEVEL 3 RSH 0 TOX 300E 10 LD 0 21E 6 8 XJ 0 3E 6 VMAX 15E4 ETA 0 18 GAMMA 0 4 KAPPA 0 5 9 NSUB 35E14 UO 700 THETA 0 035 VTO 2 231 CGSO 2
9. 3 e Current 1 lin Spe Se aaan pares a aA S A gee Se eee 25u 25 Voltage X lin VOLTS Symbol Wave _ 0 Design Type DO point usr5 k kime spices hspice examples nmos_iv DC it m1 In general for both dc and transient analyses one most be careful not to request too many or too few result points In this case there are about 5 0 0 1 50 result points O ins 100ms which requests which is reasonable To specify tran 100ms 0 1ns or about 1 billion result points clearly is not If a resolution of 0 1ns is required then the simulation time should be restricted to no more than 100 ns even for simple circuits To obtain the family of I V curves Ip versus Vps with each curve for a value of Vgs we use dc Vds 05 0 1 Vgs 05 1 probe I1 M1 14 DIGITAL CIRCUIT SIMULATION USING HSPICE SPECIFIC ANALYSES AND OUTPUT This sweeps Vds from 0 to 5 volts in steps of 0 1 volt for every value of Vgs from 0 to 5 volts in steps of 1 volt The result is a family of six curves one for each value of vgs A 5 o Voltage X lin VOLTS 5 Design Type Wave Symbol DO point usr5 k kime spices hspice examples nmos_iv DC m1 gt a l V Curve for Parameter This gives a plot of JIp versus Vps Vgs as shown on pages 69 70 of Kang and Leb Extraction lebici Ip is again I1 M1 The SPICE circuit used is NMOS Parameter Extracti
10. 3 source and 4 substrate The instantaneous power dissipated in an element is specified as P Wwww where Wwww is the element name For example the power dissipated in an MOSFET M1 is P M1 The instantaneous power dissipated in the entire circuit is denoted by key word POWER Since average power in MOS circuits has a strong transient component determination of average power requires a clear picture of current flow in the circuit in order to select a correct time interval for the measurement Also to conveniently measure the power for a portion of the circuit a separate power supply source or a OV voltage source attached to the main power supply source may be needed to supply power to the portion of the circuit 10 DIGITAL CIRCUIT SIMULATION USING HSPICE EXPRESSIONS EXPRESSIONS Algebraic expressions are of use in obtaining a number of results frequently used in device and circuit analysis In Table 2 we will summarize selected operators and func tions useful in analyzing devices and digital electronic circuits We will particularly focus on the use of expressions in analyzing and making measurements on outputs TABLE 2 Frequently used Operators and Functions in AvanWaves and HSPICE Operation Function Notation Add Subtract Multiply i Divide x to the power y pow x y Square root of x sqrt x Absolute value of x abs x Derivative of x derivative x Integral of
11. 4 98 4 docs hspiceManual pdf The various table of contents indexes and chapters can be viewed with Frameviewer by entering viewer The table of contents TOC and indexes IX are hypertext so you can click on entries to go to the content location Also Frameviewer has a Find com mand which allows you to search for keywords Alternatively a postscript version is in Postscript instead of Publish Avan Waves provides an on line help capability There is also a manual available in post script form afs engr wisc edu apps star hspice 1998 4 98 4 docs AvanWavesUG ps In case of persistent problems you might want to see if you have encountered a known bug by consulting the release notes in afs engr wisc edu apps star hspice 1998 4 98 4 docs hspice rn98 4 pdf or other documents in afs engr wisc edu apps star hspice 1998 4 98 4 docs HSPICE COMMANDS In this section we briefly describe some of the HSPICE commands The commands may be written using either upper or lower case ALTER allows statements in the file to be replaced and a new run to be performed with the new statements See the manual for more details DATA allows repeated runs to be performed with the variable values given in a data table See the manual for more details DC performs a DC analysis For example DC Vin 0 5 0 1 performs a DC analy sis using a sweep of Vin from 0 V to 5 V in 0 1 V increments END is required at the end of an HSPICE netlist
12. KAPPA 0 5 NSUB 35E14 UO 700 THETA 0 095 VTO 0 781 CGSO 2 8E 10 CGDO 2 8E 10 CJ 5 75E 5 CJSW 2 48E 10 PB 0 7 MJ 0 5 MJSW 0 3 NFS 1E10 e options post probe For I V Curve Id vs Vgs de Vgs 05 0 1 probe I1 M1 For I V Curve Id vs Vds with Vgs 2V dc vds 0 5 0 1 probe I1 M1 For family of I V Curves dc Vds 0 5 0 1 Vgs 05 1 probe I1 M1 end l V Curves For the above circuit to obtain the data to plot an I V curve using AvanWaves Ip versus Vgs we use dc Vgs 0 5 0 1 12 DIGITAL CIRCUIT SIMULATION USING HSPICE SPECIFIC ANALYSES AND OUTPUT probe I1 probe I1 M1 Vgs sweeps from 0 to 5 volts in steps of 0 1 volt The output current into the drain of M1 is Ip Vps for this analysis is the nominal value of 2V given in the HSPICE file The resulting curve is Current 1 lin 500m 1 1 5 2 25 3 3 5 4 45 5 Voltage X lin VOLTS Design Type Wave Symbol DO point usr5 k kime spices hspice examples nmos_iv DC m1 K sia To obtain the I V curve Ip versus Vpg we use dc vds 0 5 0 1 probe I1 M1 DIGITAL CIRCUIT SIMULATION USING HSPICE 13 S Family of l V Curves PECIFIC ANALYSES AND OUTPUT Vds sweeps from 0 to 5 volts in steps of 0 1 volt The output will be V 2 which is Vps and the output current into the drain of M1 which is Ip Vgs for this plot is the nominal value of 2V given in the SPICE file The resulting curve is o
13. VTC obtained is z 3 S S S s Design Type Wave Symbol DO point usr5 k kime spices hspice examples nmos_inv DC v 4 Oo eh For the NMOS inverter example the node number for the input voltage is 3 and the node number for the output voltage is 4 In this case the input voltage waveform Vin to be used Vin 3 0 PULSE 0 5 ON 0 4N 0 4N 9 6N 20N DIGITAL CIRCUIT SIMULATION USING HSPICE 17 SPECIFIC ANALYSES AND OUTPUT is in the circuit file Look at independent voltage sources to see the meaning of the vari ous numbers specifying the piece wise linear PWL or pulse PULSE waveform in the manual To perform the transient analysis we used tran 0 1ns 20ns probe tran V 3 V 4 For this command a simulation value is determined every 0 1 ns for an interval of 20 ns giving 201 result points The circuit behavior is analyzed in the time domain by using the voltage waveform specified for Vin as the input stimulus In this case the input waveform is a single pulse of 10 nanoseconds with 0 4 nanosecond rise and fall times Both the input waveform v 3 and the output waveform v 4 are plotted versus time and can be viewed with Avan Waves In addition the curve for the total instantaneous power POWER is also plotted 2 6m 2 4m 2 2m 2m Z g C 16m 5l 3 i 2 i z S C ei H Faim i ie 1 L 7 E 1 2m 1 m H m C 1m L L 1 L i C
14. also need to specify xterm in the Xterm command Ordinarily Machine and Version will be left blank Click on OK to return to the Run Manager Select the source file you wish to run on the Design list and click on Run If you wish to interrupt the run click on Stop To restart the run click on Run The Status area will give the status of the run Warning If design lis already exists then the run will end with an Error in the Status area and will not write any output files You must remove the design lis file after each run In a separate Xterm window enter rm design 1lis and then before each run on design sp enter r to remove the design 1lis file When the run completes you can examine design 1is by click ing on Listing This file provides a lot of useful information about the parameter values for the run and also indicates errors Finally to modify the source file design sp with your editor click on Source The HSPICE run will place the various results in files named design where rep resents the file extensions given in Table 1 The 1lis file will appear in design ext inTable is a sweep number or hardcopy file number AvanWaves is used to provide a high resolution interactive display of HSPICE outputs It is most easily executed from the directory containing the relevant HSPICE output files If you are not already in AvanWaves enter awaves You can access the various result files by clicking on Design Open Warning Each t
15. ave List To automate the measurement at the 2 5 V level click on Measure Mea sure Preferences and select Lock Horizontal at Y Value and enter 2 5 Then click on Apply To actually perform the measurement click on the PointtoPoint shortcut or on Measure PointtoPoint Then use the left button to select V 3 and drag to V 4 The measurement points will automatically appear at 2 5 V on V 3 and V 4 and a label appears containing Delta X the propagation delay value Plain ASCII outputs such as design 1is can be printed using the normal print com mands We advise you to edit out irrelevant text first To print from AvanWaves click on the print icon in the Shortcut menu and make the appropriate selections in the Print menus You can print to a printer or send postscript to a file Warning Use only Portrait not Landscape to print to a file Otherwise the result will be too wide to be viewed or printed DIGITAL CIRCUIT SIMULATION USING HSPICE HSPICE User s Manual and AvanWaves Help and Manual ALTER DATA DC END GLOBAL HSPICE COMMANDS To print plots from HSPICE directly you must use the GRAPH command See the on line manual for details HSPICE is a very complex and sophisticated circuit analysis tool As a consequence we have only touched upon a very small portion of its features here A three volume HSPICE User s Manual is available on line for your use See afs engr wisc edu apps star hspice 1998
16. circuit pat Subcircuit cross listing if there are subcircuits These files appear in response to corresponding MEASURE statements in design sp mt Transient analysis measurement results ms DC analysis measurement results ma AC analysis measurement results These files appear in response to OPTIONS POST and corresponding analyses in design sp tr Transient analysis results for AvanWaves SWH DC analysis results for Avan Waves ac AC analysis results for AvanWaves This file appears in response to a SA VE indesign sp Le Operating point node voltages initial conditions Zooming on the waveform display area can be achieved in three different ways 1 by clicking on Zoom in the context sensitive menu 2 by clicking on the shortcuts menu bar or 3 by clicking on Window Zoom Various measurements can be made on or between waveforms by clicking on Measure For example suppose you want to measure the propagation delay tp for an inverter with input voltage V 3 and output voltage V 4 where the 50 voltage value on the waveforms is at 2 5 V First it is necessary to make sure that the right data appears in the resulting measurement label To set up the data that appears click on Measure Label Options Then select only the option Delta X and deselect all others since the X axis of the display is Time Then click on OK Next select the two waveforms V 3 and V 4 in W
17. curve integral curve Available in AvanWaves and MEASURE only in HSPICE AvanWaves also has comparison Boolean and conditional operators MEASURE in HSPICE has functions such as average peak to peak and RMS Example Find the power consumption during a period of an applied input pulse wave of an NMOS inverter with power supply voltageVdd and depletion mode transistor M2 The duration of the transient analysis and the pulse period is 30 ns In AvanWaves we can use the Expression Builder to construct an expression power equal to integral I1 M2 5 0 60n In terms of the processing of outputs expressions such as that above can be used within HSPICE in PLOT PRINT PROBE and MEASURE statements as well as being con structed in Expression Builder Expression Builder can be opened by clicking the Expression Builder icon on the shortcut menu or by clicking Tools Expressions To build the equation above double click on integral in the Functions area to add integral to the Expression field Change the Result Browser type to Current and drag the current I1 M1 using the middle mouse button into the parentheses for integral Next drag and from the Operators area and enter 5 0 Finally drag from the Operators area to the Expres sion and enter 60n In the Result field enter power and then select Apply to cause power to appear in the Expressions area Finally select power and with the middle mouse button drag it to a panel N
18. d path kime will not work LIB is used to include text from one file in another at run time It is typically used for the models for elements such as MOS and BJT transistors and transmission lines Multi ple models may appear in the same library file Thus the model name must be specified after the file path filename for the library For example LIB pong usr5 k kime public_html1 555 spice_models scn06hp L13 NOM is used to include the models in library NOM in file scnO6hp L13 which are the nom inal level 13 BSIM models for the CMOS devices in an HP 0 6 u process Note that the abbreviated path kime will not work MEASURE abbreviated MEAS is used to make a variety of measurements on result variables MEAS TRAN avg_id AVG I1 M2 FROM 30n TO 60n assigns the aver age value of the drain current of transistor M2 over the interval from t 30 ns to t 60 ns to the variable avg_id The HSPICE manual should be consulted for the details of the many other uses of MEASURE To produce files containing measurement results OPTIONS should include MEASOUT MODEL files define the models for elements such as MOS and BJT transistors and transmission lines OPTIONS is followed by a list of parameters in some cases accompanied by parame ter values It is the main mechanism for controlling the simulation including outputs and tolerances See the manual for details PARAM is used to define a parameter that is used as a variable in
19. ecute HSPICE from a command line by simply entering hspice design gt design ext This will cause HSPICE to be executed on the netlist file design sp and will place the various result files in files named design where represents the file extensions given in Table 1 The lis file will appear in design ext Another way to run HSPICE is to simply type hspice You will be prompted for the input and output file names and will be asked to answer a number of questions Nor mally you will use the default answers REFERENCES S M Kang and Y Leblebici CMOS Digital Integrated Circuits Analysis and Design 2nd Edition New York McGraw Hill 1999 G Massobrio and P Antognetti Semiconductor Device Modeling with SPICE 2nd ed New York McGraw Hill 1993 Star Hspice Manual Version 98 4 Avant Corporation January 1998 AvanWaves User Guide Version 97 2 for use with AvanWaves Release 97 2 Avant Corporation May 1997 DIGITAL CIRCUIT SIMULATION USING HSPICE 19 FEEDBACK FEEDBACK Please e mail information on errors suggested additions or other comments on these notes to C R Kime at kime engr wisc edu 20 DIGITAL CIRCUIT SIMULATION USING HSPICE
20. esosnescessesesssosis 19 The HSPICE Netlist File An Example HSPICE File GETTING STARTED WITH HSPICE REFERENE Eases una sc nls an dhasoert E N R 19 PEEDBACK sscaveiascssnssteaneciaistucssanstvivaiosaah ins vinci bares hands state oe oe O 20 GETTING STARTED WITH HSPICE Avant s Star Hspice referred to here as HSPICE is available on the HP Unix worksta tions at CAE HSPICE executes in batch mode using the Unix command line or a graph ical user interface called AvanWaves Here we will emphasize the use of AvanWaves on HP Unix workstations with a brief section at the end on use of command line execution of HSPICE HSPICE uses a netlist filedesign sp where design is the name of your circuit as a source file This text file contains the circuit netlist element models analysis com mands and output commands Execution of HSPICE produces a number of files depend ing on user specified options By use of the appropriate options files are produced which act as the input files for AvanWaves for displaying analyzing and printing results from HSPICE In addition text files for reading and printing and graphic files for direct printing from HSPICE can be produced Although some versions of SPICE required the use of upper case letters you may also use lower case letters with this version Further this version is not case sensitive so Vin and vin are recognized as the same variable Lines containing comments begin with C
21. ime you run HSPICE you must click Panel Update to display the new results The Results Browser window con tains various output files for your circuit Clicking on a particular file in the listing and variable type in the Types area causes the corresponding variable names to appear in the Curves area To display a particular curve select it with the left mouse button and drag it with the middle mouse button to the Panel in the Results Display window Repeat the select and drag for each curve you wish to display If there are curves from a number of sweeps for a given result variable it is possible to highlight specific sweeps by double clicking on the waveform name in the Wave List This will cause the names of the individual sweeps to appear Double clicking on a spe cific sweep name will highlight that sweep If you want to display only selected sweeps you can click using the right button in the waveform display area to obtain the context sensitive menu Click on Sweep Filter and click or drag on those sweeps you want to display Then click on OK or Apply These features are illustrated in the AvanWaves tutorial DIGITAL CIRCUIT SIMULATION USING HSPICE 5 Output Printing GETTING STARTED WITH HSPICE TABLE 1 File Extensions These files appear unconditionally Lis or user specified ext Output listing including print and ASCII plot outputs st Output status This file appears if there are subcircuits in the
22. omments within other lines begin with one or more spaces followed by To continue a statement on multiple lines each line after the first must have a in the first column or each line of the statement except for the last line must end with or removes all spaces For example ABC DEF gives ABC DEF But ABC DEF gives ABCDEF An NMOS depletion mode load inverter illustrates the components of a typical digital circuit HSPICE file The numbers appearing on the right of the file are not part of the file but appear only for reference NMOS Depletion Mode Inverter file nmos_inv sp Last revised 1 11 97 Power Supplies Vdd 1 0 DC 5V mBwWdYP DIGITAL CIRCUIT SIMULATION USING HSPICE GETTING STARTED WITH HSPICE Vbb 2 0 DC 2V 5 Input Signal 6 Vin 3 0 PWL Ons OV 0 4ns 5V 14 6ns 5V 0 4ns OV 7i Vin 3 0 PULSE 0 5 On 0 4n 0 4n 14 6n 30n 8 Inverter Circuit 9 M1 4 3 0 2 NENH L 2u W 4u AD 32p 10 M2 1 4 4 2 NDEP L 4u W 2u AS 32p LL Cout 4 0 O 1lpf 12 Vout 4 0 13 Include statement to obtain MOS model file 14 INCLUDE full path to spice model nmos 3 15 16 For Voltage Transfer Characteristic VTC I7 DC Vin 0 5 0 1 18 PROBE DC V 4 19 For propagation delay and power 20 TRAN O 1ns 60ns 21 For propagation delay 22 PROBE TRAN V 3 V 4 23 For average power over one full Vin cycle 24 MEAS TRAN avgpow AVG POWER FROM 30n TO 60n 25 OPTIONS PROBE POST MEASOUT 26 END 27 The first
23. on Circuit file NMOS_PX Last revised 1 11 97 Vds Vgs Vgs 1 0 OV Vsb 0 2 OV NFET DIGITAL CIRCUIT SIMULATION USING HSPICE 15 SPECIFIC ANALYSES AND OUTPUT 3u 3u W M1 110 2 NENH L NFET Model 0 21E 6 MODEL NENH NMOS LEVEL 3 RSH 0 TOX 300E 10 LD 0 5 0 4 KAPPA 0 781 CGSO 0 18 GAMMA 0 095 VTO 15H4 ETA 700 THETA 0 3E 6 VMAX XJ 2 8E 10 NSUB 35E14 UO CGDO MJSW 0 7 MJ 0 5 2 48E 10 PB 5 75E 5 CJSW 1E10 2 8E 10 CJ 0 3 NFS options post probe For parameter extraction dc Vgs 0 5 0 1 vsb 0 3 3 PAR sqrt I1 M1 probe sqrt id end The resulting I V curves are useful for finding k Vro and GAMMA u swesed nmos parameter extraction circuit file nmos_px sp 1 5 n VOLTS Voltage X li Wave Symbol D0 A0 par sqrt_id Type Design DC DO pong usr5 k kime spices hspice examples sp nmos_px DIGITAL CIRCUIT SIMULATION USING HSPICE 16 Voltage Transfer Characteristic VTC Transient Delay Analysis SPECIFIC ANALYSES AND OUTPUT For the NMOS inverter example the node for the input voltage Vin is 3 and the node for the output voltage is 4 To obtain the VTC we used dc vin 0V 5V 0 1V probe dc V 4 This command replaces the waveform for Vin specified in the file with a signal that sweeps from 0 to 5V in increments of 0 1V For the example circuit the
24. ote that power by definition is a horizontal line Note that the various functions can be applied only to single variables not to expres sions If you wish to apply a function to an expression define the expression and give it a name and click Apply so that it appears in the Expressions area DIGITAL CIRCUIT SIMULATION USING HSPICE 11 SPECIFIC ANALYSES AND OUTPUT In order to form power within HSPICE we use MEASURE since there is no average or integral function for use outside of MEASURE Using the AVG function MEASURE power AVG POWER FROM 30n TO 60n To avoid effects of the initial conditions on the power calculation a full cycle of the input Vin precedes the beginning of the measurement SPECIFIC ANALYSES AND OUTPUT Examples are given for performing specific frequently used analyses The HSPICE files and results are available in www cae wisc edu kime 555 tool_ docs spice examples To go directly to these files on CAE Unix workstations replace www cae wisc edu kime with kime public_ html The HSPICE circuit for the I V Curve examples is NMOS I V Curve Circuit file nmos_iv sp Last revised 1 11 97 The voltage values given are nominal values to be used if not over ridden by dc or transient commands affecting the source value Vgs 10 2V Vds 2 0 2V Vbs 3 0 OV NFET M1 2 10 3 NENH L 3u W 3u NFET Model MODEL NENH NMOS LEVEL 3 RSH 0 TOX 300E 10 LD 0 21E 6 XJ 0 3E 6 VMAX 15E4 ETA 0 18 GAMMA 0 4
25. other statements in the netlist file For example suppose you want to run a circuit with different sized devices that are scaled using parameter A Then PARAM lw 0 3ucan be used for DIGITAL CIRCUIT SIMULATION USING HSPICE PLOT PRINT PROBE TRAN WIDTH OUT 80 INPUT WAVEFORMS a 0 6 u process and PARAM lw 0 2ucan be used for a 0 4 u process The device dimensions can be specified in terms of lw L 2 lw W 3 lw AD 18 lw lw AS 18 1lw lw For continuation to the next line within the single quotes use and outside of the quotes use PLOT V 2 V 3 plots selected output variables in this case V 2 and V 3 to design 1lis using ASCII characters PLOT is useful for looking at plotted results without access to AvanWaves It can also be used with OPTIONS PROBE to select the values to be placed in output files PRINT V 2 V 3 produces a printed table of node voltage values for nodes 2 and 3 in the design 1lis file It can also be used with OPTIONS PROBE to select the values to be placed in output files PROBE is used with OPTIONS PROBE to select the values to be placed in output files Unlike PLOT and PRINT it does not place results in design lis TRAN performs a transient analysis For example TRAN 0 1ns 50ns provides 501 points of transient analysis output at 0 1 ns intervals from t 0 through t 50 ns To pro duce useful output TRAN requires a waveform on
26. the 50 point with rise and fall times of 0 2 ns and a duration measured at the 50 value of 5 ns It repeats with a period of 10 ns OUTPUT VARIABLES In PROBE PRINT PLOT and MEASURE statements voltages currents power and user defined variables appear The general form for voltages is V n1 lt n2 gt where lt gt indicates optional If n2 is missing then V n1 is simply the voltage on node n1 referenced to GND If n2 is present then V n1 n2 is the voltage on node nl with reference to node n2 V n1 V n2 For a current through a voltage source the simplest form is I Vxxx where Vxxx is the voltage source name For example the current from the power supply Vdd is the negative of I Vdd To measure specific currents it is sometimes useful to add a 0 volt source Vx to generate anew node You can then output current I Vx For example this is useful for obtaining the current for calculating the power dissipation for a CMOS NAND gate In this case Vx has its positive terminal attached to Vdd and negative ter minal attached to the sources of the PFETs in the NAND For the current through a branch of an element the simplest form is In Wwww where n is the node position number of the branch on the element and Wwww is the element name For example the current into the drain of n channel MOSFET M1 is I1 M1 and the current out of its source is I3 M1 since the terminals on a MOSFET are in order 1 drain 2 gate
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