CSCI 5330Digital CMOS VLSI DesignInstructor: Saraju P. Mohanty, Ph. D.

CSCE 5730: Digital CMOS VLSI Design 1

Lecture 4: LTSPICE

NOTE: The figures, text etc included in slides are borrowedfrom various books, websites, authors pages, and othersources for academic purpose only. The instructor doesnot claim any originality.

USEFUL LINKS

• LTPSICE software available at:http://www.linear.com/designtools/software/switchercad.jsp

• 50nm model file available at:http://www.cmosedu.com/cmos1/book.htm

• More model files available at:http://www.eas.asu.edu/~ptm/

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CMOS Inverter

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Construct an Inverter using LTSPICE

• Discussion at Nano-CMOS: 50nm technology.• PMOS: 20/1 (L = 50nm/ W = 1µm)• NMOS: 10/1 (L = 50nm/ W = 500nm)• VDD: Supply voltage (Vdc = 1V).• Vin: changes depending upon analysis:• DC analysis: DC voltage (1V).• Transient analysis: Pulsed voltage (vpulse).• Wire to connect components.• Model file (cmosedu_models.txt).

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What does a model file look like ?

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Placing and connecting components

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Where to get components from ?

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Run simulation

CSCE 5730: Digital CMOS VLSI Design

How to assign W/L ?

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Interpreting a pulsed waveform

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How to assign Vin ?

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DC Analysis

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View netlist

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Transient (time) Analysis

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Creating a symbol for Inverter

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• Schematic files saved as *.asc• Symbol files saved as *.asy

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Simulation using symbol: workspace much cleaner!

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One more example: NAND gate

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