Lab 3 - ECE 421L

Created and edited by Michael Parker
Email : parkem3@unlv.nevada.edu
Last updated : September 14 2021


Pre-Lab

    - Back-up all of your previous work from the lab and the course.

    - Finish tutorial 1 seen here


Lab Overview

    The purpose of this lab is create a layout for the 10-bit DAC that was drafted and simulated in Lab #2.


Lab Procedures

    Resistor Layout 


    For our layout we will be using 10k n-well resistors for all of our resistances.


 


        In order to choose our length and width for our resistor we need to remember that,
       

R = RSquare * L/W

with the sheet resistance of an n-well resistor being about 800 ohms/square.

4.5 microns was chosen for our width and we were looking for a 10k ohm resistor which gave us the equation

10k = 800 * L/4.5u or L = 0.045/800

These results were divided by 2 in order to center the resistor about our origin.





    The length and width of your n-well can be checked with a ruler by selecting tools from the drop down menu or by pressing the shortcut K.

Click at the beginning of the line you want to measure and then click at the end, the ruler wil be present on your draft until you remove them with the shoprtcut Shift+K


     


    Schematic Layout


    Once you have the layout of your nwell resistor DRC the layout, save it, and close it. I can now begin to layout our 10-bit DAC. I created a new cell view

for this layout and instantiated my resistor i layed out in the previous step. In order to allign my resistors in parallel with each other i chose -90 as my x value and

alligned each of my later instantiated resistors to that point and varied my y values by 12 as shown below.


       


    In total 31 resistors were needed to layout my schematic, 3 for each bit of the 10-bit DAC and one leading to ground at the bottom. Once I had

layed out the resistors I needed to connect 2 resistors in series and one in parallel for each bit and connect each bitsbottom with the next bits top with

metal on the metal 1 layer.





    Pins


      Now that I connected all of the bits and the ground resistor together i needed to create pins for each of the inputs on the bits (B0-B9) as well as

ground (gnd!) and the output of the circuit (Vout).





    DRC and LVS

    During the entire design process I used DRC for every few design components added to ensure that i was not violating any rules and to prevent myself

from getting to far into the design before i was able to correct any mistakes i had made. Below is an image of my final DRC after the entire layout was complete.





    Once the DRC was completed with 0 errors I extracted my layout and compared it with my schematic with an LVS. Below is the results of that test.

   


    My design files (layouts and schematics) can be downloaded for refrence or examination by clicking here.