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Joined: 11 Aug 2004
Posts: 76
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 11 Oct 2004 3:24 How can I simulate a big circuit with paracitic resistors |
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I have designed a DAC with bandgap. After finished the layout design, I can not run post layout simulation.
There are more than 300000 instances in my extranted view. It is too slow to simulate it by spectre or Hspice. I also use StarSim to do this job. But the result has big distortion, enev I use high accurate mode.
Pls give me some advice of how can I simulate this big circuit.
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codec
Joined: 11 Sep 2004
Posts: 32
Helped: 1
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| 12 Oct 2004 16:47 Re: How can I simulate a big circuit with paracitic resistor |
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Ultrasim is the best choice I think.
As for starsim, you should set high accuracy to the critical blocks.
However, in my oppion, fast spice is to confirm the total function rather than exactly accurate performance. You my run spectre with simplified netlist.
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HCM_bucat
Joined: 29 Sep 2004
Posts: 81
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| 12 Oct 2004 18:35 Re: How can I simulate a big circuit with paracitic resistor |
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| It's imposible for Hspice to handle a circuit more than 10,000 transtors. Star-simXT and Hsim can handle that. read their manual to learn the technique how to use the tools. I saw some simulations 100 times bigger than your design went through.
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selvaraja
Joined: 01 Jun 2004
Posts: 218
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| 15 Oct 2004 4:32 Re: How can I simulate a big circuit with paracitic resistor |
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you can simplify your netlist by writing subcircuits in hspice......but carefull with
nonconverging nets.....
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thcm
Joined: 13 Jun 2004
Posts: 55
Helped: 3
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| 19 Oct 2004 14:33 How can I simulate a big circuit with paracitic resistors |
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| For large scale analog simulation, abstratction is necessary and important.I think it's not appropriate to put everything into simulator.
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dumeHCM
Joined: 30 Sep 2004
Posts: 111
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| 20 Oct 2004 3:57 Re: How can I simulate a big circuit with paracitic resistor |
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| with StarSim you can set the accuracy mode in each block. By doing this you can simulate a big circuit very fast and maintain a reasonable accuracy
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kyrandia
Joined: 23 Jun 2004
Posts: 34
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| 20 Oct 2004 8:22 Re: How can I simulate a big circuit with paracitic resistor |
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| You can do rc reduction before simulating
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jordan76
Joined: 25 Mar 2004
Posts: 177
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| 20 Oct 2004 10:20 Re: How can I simulate a big circuit with paracitic resistor |
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For your design-a DAC with bandgap, it doesn't quite make sense to me that "there are more than 300000 instances in my extracted view".
Suppose you are using RC extraction tools like Xcalibre or StarRC or LPE to get your extracted view, you had better check the manual to make sure you set the appropriate options/settings so that you can get a manageable netlist and still maintain reasonable accuracy.
Hope it will of some help to you.
regards,
jordan76
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toka
Joined: 25 Oct 2004
Posts: 13
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| 26 Oct 2004 5:40 Re: How can I simulate a big circuit with paracitic resistor |
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| I think you need add RC reduction options or some filters option to your extracted tools. One DAC of 300000 instances are too slow even for ultrasim. Most of time, you can reduce most of parasitic R&Cs with enough accuracy.
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itaifrenkel
Joined: 09 Oct 2004
Posts: 147
Helped: 20
Location: Israel
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| 26 Oct 2004 19:05 Re: How can I simulate a big circuit with paracitic resistor |
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Have you tried Nexxim ?
This new solver is HSPICE compatible and is capable of solving much larger netlists and faster
http://www.ansoft.com/products/hf/nexxim/
http://www.ansoft.com/news/press_release/041026.cfm
Itai
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devrimaksin
Joined: 13 Oct 2004
Posts: 93
Helped: 9
Location: Dallas, Texas, USA
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| 26 Oct 2004 19:17 How can I simulate a big circuit with paracitic resistors |
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It dont make sense to simulate this many
component, you have to filter out the component
that are insignificant (say resistors less than 1 Ohm)
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yakyao
Joined: 12 Oct 2004
Posts: 8
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| 28 Oct 2004 8:26 How can I simulate a big circuit with paracitic resistors |
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| I do not think starsim is a good tool. The speed is slow when simulate the mixed circuit.
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