The vgs value of MOS in the .lis file is different from the .meas result (LX2)

[mpig09]

Hi all:

My Hspice command:

*******************************************************
.op
.tran 10n 10u

.meas tran VGS_M1 param='LX2(XOPA.M1)'
==>the VGS_M1 value in the .mt0 and .lis are different.

Does the Hspice command is wrong?

Could someone help me?

Thanks.
Mike

 

[KlausST]

Hi,

Did you use identical test parameters?
How much does it differ?

Klaus

 

[mpig09]

Hi KS:

Thanks for your reply, and

1. which is identical test parameters?
2. VGS in the lis file is 473.3892mV, the measure result is 473.388mV.
diff = 1.2uV

Mike

 

[frankrose]

I don't know which simulator you are using, since hspice language and commands are available for more softwares, I think it can cause differences.

I don't know what is .lis and .mt0 files either. I guess .mt0 is the .op analysis output file, and the .meas command gives back .tran analysis result in .lis file, not sure. If that is the case, two analysis not unconditionally use the same integration method, engine accuracy settings, or your initial condition settings for .tran analysis are not the same as the final state conditions in .op analysis.

Try to set .tran analysis to run until steady state is not identified, maybe it is the reason, or modify run time, accuracy settings, integration method.

 

[mpig09]

Hi frankrose:

Thanks for your reply.

1. The Hspice version is 2013.03.
2. I set .option accurate=1 or doesn't set it,
the results are the same. (mt0 and lis file are different)
3. Wait the circuit in the steady state may not suit for me.
Because I want to check MOS operation region, for this target,
I think I need to check .lis file (from .op).
But there are may MOS need to check, so I want to use .meas.

​

If I misunderstand anything, please let me know.
Thanks.
Mike

 

[frankrose]

More softwares can use Hspice syntax, but softwares can use different settings, solver as default. But I guess you are using the original Hspice software, I don't know that.

Could you rephrase your 3rd statement and/or share more details about your project (test setup, schematic, simulator settings, what do you need exactly, why, etc.)?
And I don't understand your issue here, why you cannot create a test setup where you check the steady statement of a single MOS device and compare the output files there? If you don't see difference you could see that steady state is the reason.
Your original post didn't mention you have more devices, hard to give you a useful answer if you have important conditions which are not mentioned.