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Simulators >> Circuit Simulators >> Specify temperature of the chip in Spectre
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Message started by cmos.analogvala on May 29^th, 2009, 11:53pm

Title: Specify temperature of the chip in Spectre
Post by cmos.analogvala on May 29^th, 2009, 11:53pm

There are three ways to specify temperature in simultions in Spectre Cadence.

1. Change trise of the deivce in its properties
2. Change temperature in setup->temperature in ADE
3. Change dtemp in model file

What are the differences between all these ?
-CA

Title: Re: Specify temperature of the chip in Spectre
Post by ywguo on Jun 7^th, 2009, 10:36pm

Hi,

Quote:

1. Change trise of the deivce in its properties

Set ΔT between a specific instance and TEMP.

Quote:

2. Change temperature in setup->temperature in ADE

TEMP

Quote:

3. Change dtemp in model file

Set ΔT between a specific component and TEMP.

Yawei

Title: Re: Specify temperature of the chip in Spectre
Post by Geoffrey_Coram on Jun 8^th, 2009, 7:00am

If you're trying to get all the devices in your circuit, then 2 is the most efficient, because it's one change. 3 requires a change for every model, 1 requires a change for every instance. However, if you want different instances to have different temperatures, then 1 is your only option.

For a bug-free simulator, all three should give the same answer.

Title: Re: Specify temperature of the chip in Spectre
Post by cmos.analogvala on Jun 18^th, 2009, 8:32pm

I am simuating my circuits using spectre. I see different results for option 1 and option 2.
Option 2 shows higher degradation in current with increase in temperature.

Which one to believe ?

-CA

Title: Re: Specify temperature of the chip in Spectre
Post by Geoffrey_Coram on Jun 19^th, 2009, 4:57am

That sounds like a bug to me. Can you try options 1 and 2 on just a single transistor and check the id-vd plot?

Hmm, now I'm remembering ... in at least one foundry model library, I think I saw the circuit temperature used in the subckt, and maybe trise was omitted from the formula. (I think the temperature update equation was more complicated than what's available built into the resistor or something.)

I'd suggest just a sanity check on the transistors with the id-vd plot, then try the resistors, or open the model library file in a text editor and look at those subckts.

Title: Re: Specify temperature of the chip in Spectre
Post by cmos.analogvala on Jun 23^rd, 2009, 9:15am

Problem Solved ...
The reason was inaccurate model card which was of the older version. With the new version of the model card I found exactly same results for ID-Vd of transistor for option 1 and option 2.

Thanks a lot ..
CA