GDS to schematic conversion

[umaganesh90]

Hi All,


I want to convert GDS file to schematic..that means if they given Layer by Layer gds layout we can capture from that responsible schematic like it is opamp PLL ..It is possible any tool is there for this conversion please anybody know this method means send me...

 

[DharmaSlice]

Not that I'm aware of, do you have both schematic and GDS and you want to find the location of the different blocks or are you going in with just the GDS and hoping to extract schematic information ?

 

[erikl]

I want to convert GDS file to schematic ... is possible any tool is there for this conversion ...

AFAIR we once succeeded to manage such a method, with Cādence tools:

1. streamIn the GDS file (in Virtuoso layout or layout XL). You need an appropriate layer table. You get a layout view.
2. Extract the layout view to get an extracted view
3. Create a schematic view. Cādence' primitives' libs (sample, ...) must be accessible.
4. Import the netlist from the extracted view: File->Import->from extracted view

You get a (not pretty) schematic with correct connections, schematic primitives' symbols arranged like the devices in the layout.
The symbols' distance can be defined by an option.

 

[umaganesh90]

Hi erikl,

Thanks for your reply..I am having only gds file..here netlst means what you mean can you please explain me clearly that process..

 

[erikl]

... can you please explain me clearly that process..

Tell me what you don't understand from the 4 points mentioned above.

Do you have access to Cādence tools, and know how to handle them?

 

[umaganesh90]

I have followed the steps mentioned by you.

1. StreamIn the GDS file - Done got Layout view
2. Extract the layout view to get an extracted view - I am struck here.

For extracting I am using Calibre. This tool needs some netlist to extract the file. I have only GDS file.

It is possible to extract without any netlist? If so can you please assist me with detailed steps to try that out here. It will be very helpful for me.

Thanks in Advance.

 

[erikl]

For extracting I am using Calibre. This tool needs some netlist to extract the file.

Extracting doesn't need a netlist, but an extraction rules file is needed, which is aware of the parameters of the technology used.

Usually this comes with the PDK of the process which is used for the generated layout.
Without this PDK you probably won't have a chance to extract the layout and regenerate a schematic netlist from it, sorry!

 

[timof]

erikl - you are right, one needs to have a rule file corresponding to this GDS file and to this technology.
The most important things that rule file will provide are:

1. connectivity - which metal layer is connected to which other metal layer by which via layer
2. device recognition - so that the software understands where the devices are formed, and what these devices are, and what their layout parameters are.

I have never heard of such a need, to reconstruct schematic from the layout - in normal design flow, a schematic is done and is available prior to doing layout, extraction, etc.

But, in a hindsight, I do know about situations when people need this and they are doing this, on a routine basis - when they are doing reverse engineering. Companies like chipworks.com, performing reverse engineering services, are taking chips, and deprocess them, layer by layer, to create layout of all the layers. Then, they reconstruct the circuit schematic. For that, I guess they need to write rule deck describing connectivity and device recognition.

Also, they do all sorts of measurements - electrical (like I-Vs on individual devices), structural - layer thicknesses, etc., and so on. Then, they package this info into "reports" (structural and electrical reports) and sell it in the open market. Surprisingly, this activity is absolutely legal. Semiconductor companies are using Chipwork services, or do their own reverse engineering on competitors chips routinely, this is a standard engineering practice...

Other than for reverse engineering or similar activities - I can't think of any other applications of schematic reconstruction from the layout...

 

[Madan Kumar Nath]

GDS to schematic conversion :

@umaganesh :

You need to write a software module / script for that.
The inputs to this s/w or script will be GDS and Netlist.

1. GDS will give you the position of cells and pins.
2. Netlist will give you the connectivity between cells ( of Pins ).

Now with this information, you write a SKILL / OASIS file, which when loaded in Virtuoso, shows you the Schematic.


@timof :
Trying to answer a scenario in which its required.
In some graphical tool / script we can allow user to place the blocks of h/w that he wants to make. Now this description is given to a tool which outputs the GDS.

The user may want to see the scematic of the hardware that he made by placing it through the script / graphical tool .

In this senario, creation of a schematic from GDS would be helpful.