working with cadence

7/25/2019 Working With Cadence

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Beginners’ Workingwith Cadence using GUI

Dipankar Pal

Dept. of EEE & EI

BI!"Pilani# $. $. Birla GoaCa%pus

' (une to )* (ul )*,



To start Cadence:

• Open the terminal

• On the prompt type:csh

(enter)

• On the next prompt type: source

cshrc (enter)

• On the next prompt type: -irtuoso

& (enter)



After the irtuoso Editor/-irtuoso 0.*.,.

log12ho%e2)*342CD!.log5 window opens up, the beginner

should rst create a new li6rar+ and attach it to an existing

technolog+ li6rar+



To open a new 7i6rar+:

rom the tool6ar (top) clic! on7i6rar+ 9anager" #ext, fromthe window that pops up, selectthe option to open a new

7i6rar+" $i%e it a name, say&:+;'"



Option to attach with an

existing li6rar+ will appear"

The system installed in $oa

campus oers a number of

technolog+ li6raries to

attach new li6rar+ (&:+;') to"

or beginners gpdk)3, is an



The next logical step

would be to open a new

cell -iew under the newly

created 7i6rar+ (in this

case &:+;')"



or this clic! on the newly created7i6rar+ (in this case &:+;') from

the 7i6rar+ 9anager window

elect new cell"-iew option"#ame the cell"-iew"

*t is recommended to gi%e meaningful namessuch as &7ogic Gates', &D"<lip <lop',&Co%%on !ource !tage' and the li!e so that ata later time (when many cell"-iews2 li6raries

would ha%e been created), one can identify which



Cell"iew can be of sche%atic

or la+out (or e:tracted)"

The beginner would do the

simulation as a rst post+design

tas! and hence should selectsche%atic"



At this stage new cell"-iew (e"g" &C9=! In-erter') will

open up"

The user can now enter

herhis design on the



To enter an instance (e"g", a -Oor ./T, a 0apacitor or a source

etc") use either 6indke+s or clic!

on the icons a%ailable"

The 6indke+ &i' is for inserting an

instance"



To select a de%ice scroll o%er theli6raries and select the

appropriate one" ome commonli6raries are:

gpdk)3,: for selecting -O,

./T etc" (of dierent types)

analog li6: for selecting passi%e

components (resistor,capacitor), sources (such as

DC, IDC, I!I>, PU7!E etc"



After instances are entered,

next logical step is toconnect them by a wire"

The 6indke+ /w5 or the icon for it can be used"

The connection is usually made bydragging the wire with the left click of%ouse and releasing it upon reachingdestination (

node) to be connected)"



1sing the edit"option /fro% the

drop"down %enu5 the user can

%o-e# cop+ ... the instances2

part(s) or whole of the circuit"

To t the circuit in the centre the

6indke+ f can be used"



After the design is completed andentered, it should be sa-ed under the cell"-iew with theclick of the icon to sa%e"

*f there are errors or warnings,the same will be indicated on thecell -iew by ?ickering light on

the section where errorwarning exists.

The next logical step is



To si%ulate:

rom the tool6ar, the 7aunch icon has to be clicked" rom the

drop down menu, select the

@nalog Design En-iron%ent

(@DE7) option" A new window

called @nalog Design



echnolog+ Ale of acti-e

de-ices used in design isautomatically linked (as

concerned technolog+ li6rar+ is

already attached to user2s li6rar+"

A crosschec! is done by clicking on to %odel li6raries in drop

down %enu under set"up in



1nder the same drop down%enu, clic!ing on to si%ulator2

director2host. user should

also nd the option &spectre'

acti%e"



ome common types of anal+sis

a beginner has to do include:

ransient @nal+sis: this does

the ti%e do%ain anal+sis and

gi%es the output beha%ior(-oltage current etc") %ersus

ti%e"



DC @nal+sis: this gi%es the

6iasing infor%ation (dc sweep

etc")

@C @nal+sis1 this does

freuenc+ do%ain anal+sis and

i%es information such as ain as



To do transient anal+sis user

has to rst clic! on the @nal+sis

icon (from the tool6ar of @DE7

window), then select transient

anal+sis option from Choose

@nal+sis"



or transient anal+sis, start andstop ti%e are to be entered" The

period of input pulse freuencyof input sine wa-e decides it"1ser may also li!e to specify step

si;e, step nu%6er and t+pe ofsweep of (-oltage, current, 4)

li!e linear, logarith%ic,auto%atic 4"

This is done in the same window



#ext from the output icon of

@DE7 window the output to beplotted are to be selected"

1sually node current and net

-oltages are selected by

clicking on concerned node or



inally, the green (pla+ icon) is

to be clicked to start si%ulation" Alternati%ely one

can clic! on !i%ulation icon of

@DE7 window and select run"

*f there are no errors, si%ulation

will be successful and



5xample of DC @nal+sis is study

of %ariation of ID with respect to

D! (or DD) in a 9=!"

To do dc anal+sis user has to

rst clic! on the @nal+sis icon

(from the tool6ar of @DE7

window), then select dc anal+sis



#ext the -aria6le to be swept is

selected, e"g", D! (or DD) in

aforesaid case" To select -aria6le

from cell"-iew, user is to click on

the -aria6le icon from tool6ar of

@DE7 window"

A new window will pop up" The

user has to select the



The range of sweep (e"g", the

%ini%u% and %a:i%u% %alue of

DC (or DD) is also to be entered"

The user may also li!e to specify

the step si;e, nu%6er and t+pe

(linear, logarith%ic, auto%atic

4) in the window by entering

appropriate -alue or by selecting

6 l d i



#ow output to 6e plotted is to

be selected" /ust li!e the case of

transient anal+sis, here too

node current and or net-oltage are selected from cell"

-iew"

This is done by clic!ing output



As before, the green (pla+ icon)

can be clicked to start

si%ulation" Alternati%ely one can

clic! on !i%ulation icon of @DE7

window and select run"


will be successful and wa-efor%s



Para%etric @nal+sis To get information on stable biaspoints, 3uiescent points etc", it

becomes necessary to plot on thesame window a chain of cur%es"

5"g", it is common to plot ID %ersusD! for %arying G!" *n 0adence

this is done by para%etric

T d t i l i th



To do para%etric anal+sis, thepara%eter to be %aried o%er a

range is gi%en a -aria6le na%e and an arbitrary -alue" 5"g", usermay gi%e a -aria6le na%e, say,

G! to suppl+ -oltage (DC) that

is connected between gate and

source"

aria6le na%e is gi%en to the

instance ( in this case) by



To assign an arbitrary %alue, user

has to go to -aria6le icon from

tool6ar of @DE7 window and

from the list that appears in drop

down %enu, set a %alue to

# t t i t t t l i



#ext step is to go to tools icon

from tool6ar %enu of @DE7

window" A drop down %enu will

appear from where user has toclick on para%etric anal+sis" A

new window will appear" *n this

window user has to select %ariable



*n options table that appears,

enter %ini%u% and %a:i%u% -alue or range o%er which the

para%eter is %aried" 1ser may

also li!e to specify step t+pe

(linear, logarith%ic, auto%atic

4), si;e, or nu%6er of steps"

After ma!ing appropriate selection



After ma!ing appropriate selection

as per re3uirement, user may

click on green icon (pla+ sign)

from para%etric anal+sis

window"

5xample of @C @nal+sis is:fre3uency domain beha%ior of

circuits" To do @C @nal+sis user



#ext the freuenc+ range is

selected + usually from * to *))9 (h6)"

1nder output option user can go

to calculator and select

para%eter to be %iewed (e"g", for

gain, ratio of output node



.efore running the si%ulation,

user has to assign appropriate%alue to input (in freuenc+

do%ain)"

This is done by selecting instance

and going to properties# then

assigning appropriate -alue to

para%eter (e"g", ac %agnitude)"

#ow as earlier green (pla+



#ow, as earlier, green (pla+

icon) is clicked to start

si%ulation" Alternati%ely one can

clic! on !i%ulation icon of @DE7 window and select run"


will be successful and the



e f u n

w i t h C a

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