Cad Wiki for Analog IC Courses

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=====Cadence Setup for CPEG 424/624: Analog IC Design with Sky130 =====


Login to the ECE Linux VM **cpeg424.ece.udel.edu** using the **VNC Client**. 


==== Setting up the Sky130 PDK  ==== 

1) Open the ''.bashrc'' file in your home directory. If it doesn't exist already, then create one using a text editor such as gedit 
<code>
cd
gedit .bashrc &
</code>

Add the following lines to the ''.bashrc'' file in your home directory. 
<code>
export CDSDIR=/software/Cadence/IC618
export SKY130_DIR=/usa/vsaxena/pdks/SKY130/sky130_release_0.1.0
# Update the Spectre PATH installed on the VM
export MMSIM_PATH=/software/Cadence/SPECTRE191
export PATH=$PATH:$CDSDIR/tools/bin
export PATH=$PATH:$CDSDIR/tools/dfII/bin
export PATH=$PATH:$CDSDIR/tools/lib/64bit
export PATH=$PATH:$MMSIM_PATH/bin
export PATH=$PATH:$MMSIM_PATH/tools/bin
export PATH=$PATH:$MMSIM_PATH/tools/lib
# Need to add PVS to the PATH

# Add this line, otherwise LVS will not work
export CDS_Netlisting_Mode="Analog"

# Add this line so that ADE works on our 64-bit machine
export CDS_AUTO_64BIT=ALL
</code>

Save the above file. Then in the command line, refresh the bash shell
<code>
source .bashrc</code>


<note important>**Make sure the Cadence netlisting is set to Analog in your .bashrc as shown above, otherwise LVS will not work correctly!**</note>

2) Copy the ''.cdsenv'' file into your home directory. Please **be mindful of the dot**, i.e. ".", in the filename
<code>
cp    /usa/vsaxena/pdks/pdks/SKY130/cdssetup/cdsenv  .cdsenv
</code>


3) Create and descend into your course work directory, e.g. ''analog_course''. Better create a new directory for every course you take.
<code>
cd
mkdir analog_course
</code>

Descend into the newly created course directory and work inside this folder :!:

<code>
cd analog_course
</code>


4)  If you have existing files, save backups of the files below, otherwise skip this step
<code>
cp .cdsinit  .cdsinit_bkp 
cp cds.lib  cds.lib_bkp 
</code>

5) Copy the ''.cdsinit'' from the SKY130 setup directory using the command below to your into the ''analog_course'' directory. Again, **be mindful of the dot**, i.e. ".", in the filename

<code>
cp    /usa/vsaxena/pdks/SKY130/cdssetup/cdsinit  .cdsinit
</code>

<note important>**Make sure you have this ''.cdsinit'' file copied into the analog_course folder and not your home directory.**</note>

6) If you don't have an existing ''cds.lib'' file, then copy the ''cds.lib'' file using the following command:

<code>
cp    /usa/vsaxena/pdks/SKY130/cdssetup/cds.lib  cds.lib
</code>

7) You should be ready to start Cadence Virtuoso now!  Always start virtuoso from your analog_course directory (and not the home directory)

<code>
virtuoso &
</code>

<note important>**Always start virtuoso from your analog_course directory (and not your home directory).**</note>

**This completes your Cadence setup for the CPEG 424/624 course.**  You can move on to the [[cad_tutorials|Cadence Video Tutorials]] now.

-----



-----

===== Simulation Models =====

=== 180nm CMOS Models ===  
180nm CMOS models are located in the following directory on the VM server.

<code> /usa/vsaxena/pdks/SKY130/sky130_release_0.1.0/models </code>

**sky130.lib.spice** : Skywater 130nm CMOS models with tt, ss, sf, fs and ff process corners.  

=== 1um and 50nm CMOS Models ===  
The 1um and 50nm CMOS models are located in the following directory on the VM server.

<code> /usa/vsaxena/pdks/models/ </code>

**cmos_1u.txt:**  1um CMOS models  

**cmos_50n.txt:** 50nm CMOS models  

-----

===== Process Design Rules =====

We are using a **0.18 micron 6 Metal 1 Poly** (1.8V) CMOS technology for chip layout. In PDK specific terms, we will use **SUBM_DEEP** design rules with lambda(λ) equal to 0.09 micro meters with Lmin=2λ. Note that this λ is not the channel length modulation parameter!


The design rules are available as a {{ :wiki:scmos_180nm.pdf | PDF}} and also in [[https://www.eecis.udel.edu/~vsaxena/Cadence/SCMOS_rules/MOSIS_Layer_Map_for_SCN6M.html|Web Browsable Format]].


Note that the design rules are given in terms of λ while Cadence Virtuoso uses absolute values without any scaling. Thus in your layouts, multiply all design rule numbers by 0.09u for final layout dimensions. E.g. the minimum N-well width of 12 translates into 12*0.09u=1.08u in Virtuoso layout.

-----
===== Process Characterization Results ===== 
The process characterization results are available as: {{ :wiki:tsmc018_info.pdf |}}. You can find numerical values for the various resistances and capacitances in the process.

-----


-----

===== CMOS Book Examples =====

If you are interested, you may add Prof. Baker's CMOS book examples by adding the following line to your cds.lib file

<code>
SOFTINCLUDE /usa/vsaxena/CMOSedu/CMOS_cds.lib
</code>

**Note:** Please do not re-download Prof. Baker's CMOS Book examples from http://cmosedu.com and/or install the NCSU PDK as directed in the CMOSEdu tutorials. They are already installed and available in your course directory and can be seen in the Cadence Library Manager.
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