Set up schematic capture

ELE 5260 CMOS Integrated Circuits (2007-08 1st Semester)

Tutorial 3b: Setting up the Schematic Capture

[Any example used in this note may/may not be related to any part of homework]

In this tutorial note, you will learn how to create a schematic capture. (Note: Your library list may be different from the one stated in this note.)

A. Create a Schematic Capture

1. In Tutorial Notes 01, Part B, we have successfully created the Library: hw1 and Cell

inverter. Now, we need to create a Schematic Capture under this Cell by setting the following options.

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The Chinese University of Department of Electronic Engineering

ELE 5260 CMOS Integrated Circuits (2007-08 1st Semester)

2. As you click “OK” in the Create New File window, the “Virtuoso Schematic Editing”

window will be prompted out automatically.

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The Chinese University of Department of Electronic Engineering

ELE 5260 CMOS Integrated Circuits (2007-08 1st Semester)

3. In the “Virtuoso Schematic Editing” window, you can choose Add Î Instance… in the schematic capture window in order to import the necessary schematic symbols.

Zoom in Zoom out You can click this icon to add the necessary schematic symbols. Used for connecting components

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The Chinese University of Department of Electronic Engineering

ELE 5260 CMOS Integrated Circuits (2007-08 1st Semester)

4. The “Add Instance” window will prompt out. You just need to click the Browse button in

this window, the “Library Browser” – “Add Instance” window will prompt out too. You can select the required schematic symbols in the “Library Browser” window. The detailed selection will be discussed in the next part.

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The Chinese University of Department of Electronic Engineering

ELE 5260 CMOS Integrated Circuits (2007-08 1st Semester)

B. Select correct schematic symbol components

This part will give you a guideline to choose the correct component in the schematic view in order to simulate smoothly.

i) Adding MOSFETs

The first two things we need to use are NMOS and PMOS. The symbols of PMOS and NMOS in Cadence are shown below. Symbol (Used in lecture notes) PMOS NMOS The side with higher potential The side with lower potential is source is source Symbol (In Composer)

Note that the symbol is different to those used in lecture notes.

The PMOS and NMOS are located at the library PRIMLIB, with the cell name pmos4 and nmos4 respectively. (Note: Use pmos4 and nmos4 only, do not use other pmos and nmos)

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The Chinese University of Department of Electronic Engineering

ELE 5260 CMOS Integrated Circuits (2007-08 1st Semester)

As you select one Cell in the Cell View column, there are several choices in the View column. You just select symbol for the schematic drawing.

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The Chinese University of Department of Electronic Engineering

ELE 5260 CMOS Integrated Circuits (2007-08 1st Semester)

When you try to add the pmos4 and nmos4, you have to input values for a few parameters.

Width of the MOSFETLength of the MOSFET

Note that in Cadence, if you want to input 10um for the field, you need to input as 10u M but not 10uM. The same rule holds for other fields such as frequency, voltages, etc….. ii) Adding Passive Components Passive Components (R, L and C) are located in the library analogLib

The analogLib consists of many components; you can press once the Category button, and then choose Passives in the Category column.

Capacitor: cap Inductor: ind Resistor: res

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The Chinese University of Department of Electronic Engineering

ELE 5260 CMOS Integrated Circuits (2007-08 1st Semester)

iii) Adding Sources

Next, we need to add voltage or current sources. They are also divided into dependent sources and independent sources.

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The Chinese University of Department of Electronic Engineering

ELE 5260 CMOS Integrated Circuits (2007-08 1st Semester)

a. Independent Source:

The independent sources are also located in analogLib, but in the category Sources Î Independent

Some common sources will be introduced in the following.

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The Chinese University of Department of Electronic Engineering

ELE 5260 CMOS Integrated Circuits (2007-08 1st Semester)

vdc: DC voltage source

The DC Voltage of the source

vsin: Sine wave voltage source

These two parameters are useful for ac simulation (frequency response) only The amplitude of the sine wave

The frequency of the sine wave Page 10

The Chinese University of Department of Electronic Engineering

ELE 5260 CMOS Integrated Circuits (2007-08 1st Semester)

vpulse: Square pulse voltage source

The two voltage levels The rise and fall time The pulse width (time to stay at voltage 2) i

The period of the wave Page 11

The Chinese University of Department of Electronic Engineering

ELE 5260 CMOS Integrated Circuits (2007-08 1st Semester)

b.

Dependent Sources:

Dependent sources are located at the analogLib under the category Sources Î Dependent.

The four common sources are:

1. Voltage Controlled Voltage Source (vcvs) 2. Voltage Controlled Current Source (vccs) 3. Current Controlled Voltage Source (ccvs) 4. Current Controlled Current Source (cccs)

The four dependent sources have similar settings, so I just introduce the current controlled current source.

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The Chinese University of Department of Electronic Engineering

ELE 5260 CMOS Integrated Circuits (2007-08 1st Semester)

Enter the instance name of the reference voltage source (the words in red) Current gain (if gain = 1, that means if there is 1mA current flowing through the reference source, this cccs produces 1mA current.)

c.

The ground

The last and the most important component is the ground. It is placed under the analogLib Î Sources Î Global named gnd. d. The Global Vdd Symbol

The vdd symbol is useful if you want to connect many points to the supply within the whole schematic (even if you have a symbol containing smaller blocks of circuits). The vdd symbol is located under analogLib Î Sources Î Global named vdd.

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The Chinese University of Department of Electronic Engineering

ELE 5260 CMOS Integrated Circuits (2007-08 1st Semester)

Note that you need to define a potential to the vdd before you use it. (If you do not define the value of vdd by independent sources, it is considered as floating.)

C. Example:

Now you should know where the required components are. Before we start the simulation, try to construct the following circuit using the composer.

V1 = 0V V2 = 5V Rise time = 1n s Fall time = 1n s Pulse width = 9n s Period = 20n s Page 14