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uncle_ezra

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Posts: 90

Re: Question about Mote Carlo mismatch model file
Reply #15 - May 11^th, 2005, 10:49pm

Hi all,

How do I vary vth without actually using a voltage source and varying it by delta? Below is what I tried to do but it does not work. What name should I give to subckt?

statistics{
mismatch{
vary vth0mis_n dist=gauss std=3e-3
}

inline subckt nmos (d g s b)
parameters w=1u l=1u
nmos (d g s b) nmos w=w l=l

model n_bpw_33_mm bsim3v3
type=n
+ vth0 = 0.6+dvth0+vth0mis_n/(w*l)

Thanks

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uncle_ezra Community Member Offline Posts: 90	Re: Question about Mote Carlo mismatch model file Reply #16 - May 12^th, 2005, 12:55am Actually could someone provide a working template for monte carlo simulation. It would be very helpful. thanks
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uncle_ezra

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Posts: 90

Re: Question about Mote Carlo mismatch model file
Reply #17 - May 12^th, 2005, 1:37am

So this is the model provided in Cadence help:

library monteLib

section param
simulator lang=spectre
parameters PiRho=2500 PbRho=200 npnbeta=145.5 pnpbeta=200parameters rin1=1000 rin2=5000 rout1=1000 rout2=3000parameters cin=1.7e-08 cloop=1e-09parameters mmstat=1 initstat=1
function Rpb(l,w)=(PbRho*l/w)function Rpi(l,w)=(PiRho*l/w)
endsection param

section stats
simulator lang=spectre

statistics {
process { vary PiRho dist=gauss std=350 vary PbRho dist=gauss std=50 vary npnbeta dist=lnorm std=.9 vary pnpbeta dist=lnorm std=1.1 vary Rin dist=gauss std=150 vary cin dist=gauss std=20p vary rin2 dist=gauss std=100 vary Cfb dist=gauss std=.58n vary rout1 dist=gauss std=30 vary rout2 dist=gauss std=50 }

mismatch { vary PiRho dist=gauss std=19 vary PbRho dist=gauss std=3.75 vary npnbeta dist=gauss std=4 vary pnpbeta dist=gauss std=6 }}
endsection stats

section models
simulator lang=spectre
inline subckt npn (C B E S)
parameters brvbe=.6model
mynpn bjt type=npn is=5.771e-17 bf=npnbeta nf=0.9895 vaf=201.6
+ ikf=0.01573 ise=8.976e-18 ne=1.179 br=3.204 nr=0.9944
+ var=27.03 ikr=0.0003047 isc=1.505e-13 nc=1.912 rb=8.706
+ irb=0.001509 rbm=5.833 re=111.8 rc=54.97 xtb=1.5 eg=1.11
+ xti=3 cje=1.983e-12 vje=0.4818 mje=0.2486 tf=0.33e-9
+ xtf=4.359 itf=0.01753 ptf=176.2 cjc=1.749e-12 vjc=0.5989
+ mjc=0.3349 xcjc=0.5 tr=400e-9 cjs=1e-12 vjs=0.75
+ mjs=0.33 fc=0.5 bvbe=brvbe bvce=1

npn (C B E S) mynpn
ends npn

inline subckt pnp (C B E S)
model mypnp bjt type=pnp
+is=1.2e-16 bf=pnpbeta nf=1.00 vaf=26.00
+ikf=70e-06 ise=1.1e-15 ne=2.00 br=13
+nr=1.00 var=10.00 ikr=100e-06 isc=7.0e-15
+nc=2.50 rb=100
+re=15 rc=150 cje=33e-15 vje=740e-03
+mje=330e-03 tf=2.50e-09 xtf=1.00
+itf=2.00e-03 ptf=5.0 cjc=130e-15 vjc=690e-03
+mjc=440.00e-03 xcjc=500.00e-03 tr=5.00e-09 cjs=200e-15
+vjs=590e-03 mjs=440.00e-03 xtb=780e-03 eg=1.200
+xti=1.80 kf=1.60e-15 af=1.00 fc=850.00e-03

pnp (C B E S) mypnp
ends pnp

endsection models

endlibrary monteLib

Where does the name "subckt npn (C B E S)" come from?
Also isnt the model file in a separate file? Can you just modify it???

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Andrew Beckett Senior Fellow Offline Life, don't talk to me about Life... Posts: 1742 Bracknell, UK	Re: Question about Mote Carlo mismatch model file Reply #18 - May 17^th, 2005, 10:24am Did you read http://www.designers-guide.org/Modeling/montecarlo.pdf? Regards, Andrew.
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jimi

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Posts: 4

Re: Question about Mote Carlo mismatch model file
Reply #19 - Sep 6^th, 2005, 10:03pm

A working example for TSMC 0.13 um process.

section tt
...
// add following
parameters avt_nch=0
parameters avt_pch=0
statistics {
process {
vary avt_nch dist=gauss std=0
vary avt_pch dist=gauss std=0
}
mismatch {
vary avt_nch dist=gauss std=4.6
vary avt_pch dist=gauss std=3.95
}
}
inline subckt nch (d g s b)
parameters w=1u l=1u
nch (d g s b) nch_mc w=w l=l m=1 region=triod
include "cl013g_fsg_mc.scs" section=mos
ends nch

inline subckt pch (d g s b)
parameters w=1u l=1u
pch (d g s b) pch_mc w=w l=l m=1 region=triod
// end of jimi's code
include "cl013g_fsg_mc.scs" section=mos
ends pch

endsection tt

// then change model name nch in setion mos to nch_mc

The monte carlo works well for m=1, but for m=n, the std is n times instead of sqrt(n), still need some help and feedback to correct it!
Good luck!

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xtal

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Posts: 5
Salt lake city

Re: Question about Mote Carlo mismatch model file
Reply #20 - Dec 29^th, 2007, 5:53pm

Hi all,
I am trying to do a mismatch analysis (monte carlo simulation). I am using the Chartered semiconductor 180nm library using BSIM3v3,

I want to vary the threshold voltage for each transistor in my circuit for each simulation. However, I am getting the same delay for all 20 runs of the monte carlo simulation.

From reading the topic (and also some of the other related topics in this forum), I understand that in order to vary the threshold voltage (device paramater), I need to vary the width/ length of the transistor. Is this correct? or i can vary the threshold voltage directly.

My Library file is like this:

library MyLib

section param // I added this section
simulator lang = spectre // I added this section
parameters vth_variable1 = 1 // I added this section
parameters vth_variable2 = 1 // I added this section
endsection param // I added this section

section stats // I added this section
simulator lang = spectre
statistics {
mismatch {
vary vth_variable1 dist=gauss std=0.1
vary vth_variable2 dist=gauss std=0.1
}
}
endsection stats // I added this section

section monte_carlo // I added this section
include "sm093001-1k.scs" section=param
include "sm093001-1k.scs" section=ntn_typ
include "sm093001-1k.scs" section=stats
include "sm093001-1k.scs" section=ptn_typ
include "sm093001-1k.scs" section=hdif
endsection monte_carlo // I added this section

section ntn_typ // section already provided in the library
//
// model = bsim3
// NewModel = 3
// MetaSoftware Compatibility Mode
// These are BSIM3v3 Model Parameters
// LotName=LOT_NAME UserName=USER Date=03-01-2001
model nmos_1p8 bsim3v3 {
1: type=n lmin=1.8000000e-07 lmax=0.00000025 wmin=2.19999998807907e-07 wmax=4.39999997615814e-07
+ tnom=25.0 paramchk=1 version=3.2 ......... and all other parmaters

// model = bsim3
// NewModel = 3
// MetaSoftware Compatibility Mode
// These are BSIM3v3 Model Parameters
// LotName=LOT_NAME UserName=USER Date=03-01-2001
// Typical Models nmos_1p8 ***
2: type=n lmin=1.8000000e-07 lmax=0.00000025 wmin=4.39999997615814e-07 wmax=8.00000011920929e-07
+ tnom=25.0 paramchk=1.................................and all other paramaters

/ /
}
endsection ntn_typ

Now in this model, there are paramteres defined for each width and length like if i give the width of the transistor as 3u then it picks up the the 4th part in the model ntn_typ
So in the 4th part where vth0 was defined, I changed it to "vth0=0.3340089*vth_variable1".

However, i am getting the same delay in all simulations.

Please help me on this.

Manohar

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Geoffrey_Coram

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Posts: 1999
Massachusetts, USA

Re: Question about Mote Carlo mismatch model file
Reply #21 - Jan 2^nd, 2008, 4:52am

xtal wrote on Dec 29^th, 2007, 5:53pm:

From reading the topic (and also some of the other related topics in this forum), I understand that in order to vary the threshold voltage (device paramater), I need to vary the width/ length of the transistor. Is this correct? or i can vary the threshold voltage directly.

You can vary the threshold voltage directly; you seem to have done this in your example.

Quote:

Now in this model, there are paramteres defined for each width and length like if i give the width of the transistor as 3u then it picks up the the 4th part in the model ntn_typ
So in the 4th part where vth0 was defined, I changed it to "vth0=0.3340089*vth_variable1".

I think there's something wrong with your section set-up. In your netlist, what is your library statement?

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If at first you do succeed, STOP, raise your standards, and stop wasting your time.

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John O Donovan

Junior Member

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Posts: 29
San Jose, CA

Re: Question about Mote Carlo mismatch model file
Reply #22 - Jan 16^th, 2008, 9:35am

Hi,

You can vary some model parameters directly on the instance using the following parameters

delvto : shift in zero-bias threshold voltage (default = 0.0)
delk1 : shift in body bias coefficient (default = 0.0)
delnfct : shift in subthreshold swing factor (default = 0.0)

These are valid parameters for bsim3v3 and bsim4

So if you have a model file that defines a model nmos_1p8 as in your example (which contains multiple bins), you could simply do the following

parameter mm_vto = 0.0
statistics {
mismatch {
vary mm_vto dist=gauss std=0.1
}
}

inline subckt nmos_1p8_mm d g s b
parameters l w
nmos_1p8_mm d g s b nmos_1p8 l=l w=w delvto=mm_vto
ends nmos_1p8_mm

m1 1 2 3 4 nmos_1p8_mm l=1u w=0.2u
m2 1 2 3 4 nmos_1p8_mm l=1u w=0.2u

Here you create a mismatch variable "mm_vto", and use the instance "delvto" parameter to directly modify vt0 of the instance. By creating the subckt nmos_1p8_mm, m1 and m2 in the example will have different values for "delvto" during mismatch analysis.

Regards,
John

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