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Prof. Vojin G. Oklobdzija

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Presentation on theme: "Prof. Vojin G. Oklobdzija"— Presentation transcript:

1 Prof. Vojin G. Oklobdzija
VLSI Prof. Vojin G. Oklobdzija References (used for creation of the presentation material): [1] Mead, Conway, “Introduction to VLSI Systems”, Addison Wesley Publishing. [2] Glasser, Dobberpuhl, “The Design and Analysis of VLSI Circuits”, Addison Wesley Publishing. [3] Weste, Eshraghian, “Principles of CMOS VLSI Design”, Addison Wesley Publishing. [4] Shoji, “CMOS Digital Circuits Technology”, Prentice Hall.

2 Prof. V.G. Oklobdzija: High-Performance System Design
Historical Overview nMOS era: Pass-transistor design CMOS existed early but took off 1985 on Domino CMOS, 1982 NORA DCVSL CPL, DPL DCVS-PG SRPL LEAP SOI-CMOS Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

3 Prof. V.G. Oklobdzija: High-Performance System Design
n-MOS Design Era LSI started with nMOS: pass-transistor design experience: Flourished at the beginning of the nMOS era (popularized by Mead-Conway book) Allows high density layout and compact design style Fast: outperforming gate based design Low in power Drawbacks: Not compatible with existing design tools Exhibiting testability and reliability problems Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

4 Prof. Vojin G. Oklobdzija
Review of CMOS Prof. Vojin G. Oklobdzija

5 Prof. V.G. Oklobdzija: High-Performance System Design
CMOS Basics Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

6 Prof. V.G. Oklobdzija: High-Performance System Design
CMOS Basics Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

7 Prof. V.G. Oklobdzija: High-Performance System Design
CMOS Basics Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

8 Prof. V.G. Oklobdzija: High-Performance System Design
CMOS Basics A complex path example: Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

9 Prof. V.G. Oklobdzija: High-Performance System Design
CMOS Basics More complex blocks are realizable in CMOS Primitive gates: Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

10 Prof. V.G. Oklobdzija: High-Performance System Design
CMOS Deficiencies: Muli-Input NOR function in CMOS is slow Various remedies: Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

11 CMOS Deficiencies and Remedies
Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

12 CMOS Deficiencies and Remedies
Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

13 Prof. V.G. Oklobdzija: High-Performance System Design
CMOS Basic Inverter Transfer function: Logic voltage levels are VOH and VOL and VIL and VIH The inverter transfer function lie within the shaded region Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

14 CMOS Basic: Inverter Characteristic
Leakage Currents Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

15 CMOS Basic: Inverter Characteristic
Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

16 CMOS Basic: Inverter Characteristic
Transistors during the transition Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

17 CMOS Basic: Inverter Switching
Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

18 Prof. V.G. Oklobdzija: High-Performance System Design
CMOS Basic: Power During the static state there is no current Current is only present during transistion: Short circuit current (crow-bar current) Charging and discharging of the output capacitor Leakage Current Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

19 Prof. V.G. Oklobdzija: High-Performance System Design
CMOS Basic: Power PCMOS=kCLV2DDfo This is an E=mc2 of low-power design There are three ways to control power: Reducing Power-Supply Voltage (most effective !!) Reducing the switching activity k (various ways) Reducing CL (technology scaling etc.) Reducing the required frequency of operation (?) Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

20 Prof. V.G. Oklobdzija: High-Performance System Design
CMOS Basic: Delay Which one of the three designs is the fastest ? How can we find this out without simulation ? Learn about Logical Effort ! Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

21 Prof. V.G. Oklobdzija: High-Performance System Design
CMOS Basic: Delay Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

22 CMOS Basic: Delay RND7Cin1+RNORCin2+RND2Cout
Delay can be approximated with: RND7Cin1+RNORCin2+RND2Cout Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

23 Prof. V.G. Oklobdzija: High-Performance System Design
CMOS Basic: Delay Delay of a signal path in CMOS logic is dependent on: Fan-in of a gate Represented as a resistance of the pull-up/down transistor path of the gate Fan-out of a gate Represented as a capacitive load at the output Number of CMOS blocks in the path. Wire delay connecting various blocks. Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

24 Prof. V.G. Oklobdzija: High-Performance System Design
CMOS Basic: Delay Delay of a signal path in CMOS logic can be reduced by: Making the transistors larger in order to minimize resistance of a pull-up/down path in the gate Making the transistors smaller in order to minimize the capacitive load of each gate Reducing the number of CMOS blocks in the path. Bringing the blocks closer and/or choosing the less wire intensive topology. Note that these requirements are often contradictory Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

25 Prof. V.G. Oklobdzija: High-Performance System Design
CMOS Basic: Delay How to estimate delay and critical timing in CMOS circuits ? How to determine the proper transistor sizing in order to make a compromise with contradicting requirements ? How to choose the right circuit topology ? The Answer: “Logical Effort” Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

26 Pass-Transistor Design
Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

27 Pass-Transistor Design
Another way of looking at Karnaugh Map: AND function Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

28 Pass-Transistor Design
Two-variable function Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

29 Pass-Transistor Design
“Threshold Voltage Drop” problem: Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

30 Pass-Transistor Design
Solving the “Threshold Voltage Drop” problem in CMOS: Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

31 Pass-Transistor Design
Function Generator Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

32 Pass-Transistor Design
Full 1-bit Adder Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

33 Pass-Transistor Design
Compact ALU Example (IBM PC/RT) Circ. 1984 Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

34 Prof. V.G. Oklobdzija: High-Performance System Design
Control Lines Output Control A - inputs B - inputs Odd Even Operation K1 K2 Qn A B Arithmetic A+B Add 1 A+B+1 A-B Subtract B-A B+1 Increment +1 2s compl A+1 Logical Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

35 Pass-Transistor Design
Compact ALU Example (IBM PC/RT) Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design

36 Using Pass-Transistor Design to Speed-up Addition
Fall 2004 Prof. V.G. Oklobdzija: High-Performance System Design


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