Lab1

ENGR338 Lab 2021 Spring
Lab 3 Layout the R-2R DAC
Name: Keon Nez
Email: ktnez@fortlewis.edu

Layout the R-2R DAC

Introduction

Using Electric VLSI to draw schematics and to do integrated circuit layout with N-well resistors. Handling hardware description languages from the ADC-DAC files with LTSpice and VLSI. Familiarizing ourselves with a state of the art computer aided design system for VLSI circuit design. To help setup and anaylze the Electric/LTSpice configuration.

Materials

Operationg Systems: Electric VLSI and LTSpice
Libraries of the ideal ADC/DAC - Found here
Reference simulations and configurations from Lab 2

Methods

Understand the operation of the ideal ADC and DAC
Design a R-2R DAC in Electric VLSI to replace the ideal DAC
Be familiar with Electric VLSI and LTSpice for integrated circuit design

Task 1.) Copy the existing ideal ADC-DAC files to the ENGR 338 library and run the simulation.
Task 2.) Build the schematic of the R-2R DAC and the simulation.

Results

Task (1)

Starting with the reason that we prefer using this structure as a subcell is that we can create a layout of the subcell and copy/paste it to form the R_2R ladder.
This is a very important trick in the VLSI design.

After the subcell is done, I performed DRC/LVS check to ensure that the subcell is working. Then created an icon from it.
On to creating a new schematic view, call it 'R_2R_Ladder' to differentiate it from the one in Lab 2. Copying and paste 10 of this in this view. To create a icone for this ladder.

Run DRC: To ensure that it is DRC clean.

Task (2)

The ADC is ideal so we can't create a layout of it. Let's just replace the DAC we created in Lab 2 in the simulation and run it. Because this DAC has passed NCC (LVS) with the layout view, if the schematic works, we can say the layout is correct too. They have the same netlist and electrical connections which were verified by NCC (LVS).
Next the R-2R Ladder DAC icon was used in a copy of the simulation used in the R-2R Ladder DRC connected to the ideal subcells.

Simulation results in LTSpice of replacing the DAC with the 'R_2R_Ladder'.

Discussion
I understood the operation of the ideal ADC and DAC files from ENGR 338 library. Overall analyzing the R-2R network brings back memories of the seemingly infinite variety of networks that you’re asked to solve during electrical engineering studies (networks). The reality though, is that the analysis of this network and how it works is quite simple. By methodical application of Thevenin Equivalent circuits and Superposition, we can easily show how the R-2R circuit works.The R-2R resistor ladder based digital-to-analog converter (DAC) is a simple, effective, accurate and inexpensive way to create analog voltages from digital values.