EE 5323 Project16 Bit Sklansky Adder

Phase 2 Report

Yuan Xu4139225

xuxxx488@umn.edu

Contents• Summary• Design Optimization & Changes• Waveforms of test cases• Schematic & Layout• maximum operating frequency VS. VDD• Power consumption at the maximum

operating frequency VS. VDD• Netlist• DRC,LVS results

Summary

• The goal of this project is to realize 16bit Sklansky adder by using static CMOS devices.

• Sklansky adder belongs to tree adder family.• The difference between Sklansky adder and

other tree adders is prefix network.• Compare to other tree adders, Sklansky adder

has minimum logic levels, wiring tracks, but maxinum fanout. Also, it has largest delay at the same condition.

Summary

1:0

2:03:0

3:25:47:69:811:1013:1215:14

6:47:410:811:814:1215:12

12:813:814:815:8

0123456789101112131415

15:014:013:012:011:010:0 9:0 8:0 7:0 6:0 5:0 4:0 3:0 2:0 1:0 0:0

Structure of 16 bit Sklansky Adder(Black square is dot operator

Grey square is empty dot operatorWhite triangle is buffer)

Reference List• D.Harris, “ A Taxonomy of Parallel Prefix Networks, Signals ”, Systems

and Computers, 2003. Conference Record of the Thirty-Seventh Asilomar Conference on, 2, 2213-2217 Vol.2,2003

• J. Sklansky, “Conditional-sum addition logic,” IRE Trans. Electronic Computers, vol. EC-9, pp. 226-231, June 1960.

• J M. Rabaey, A. Chandrakasan, B. Nikolic, “ Digital Integrated Circuits-A Design Perspective (Second Edition)”, Prentice Hall, 2003

• Wu,S.D.,Chun-Chi Tsai, Yang,M, “A VLSI Layout Legalization Technique Based on a Graph Fixing Algorithm”, VLSI Design, Automation and Test, 2006 International Symposium on, 2006, 1-4

• Mason, J.S.B.; , "Layout tecbmques for mixed-signal VLSI design," Systems on a Chip (Ref. No. 1999/133), IEE Colloquium on , vol., no., pp.8/1-8/11, 1999

Design Optimization and changes

• Sizing the gate to minimum size (90nm) reduces power

• By using bubble shifting, we save totally 28 inverters, and 4 inverters on the critical path

• Adding the buffer can effectively reduce delay. Setting stage=1, fanout=4

• Minimizing each block to reduce area• Combining VDDs of different devices to reduce

area

Design Optimization and changes

• Combining Nwell and Pwell of different devices to simplify the layout

• Using fewer metal layers (2 layers) to reduce complexity and capacitance

• Changes: Fixing some flaws (body not connected to ground) in schematic

Waveforms of test cases

• Worst case: For Sklansky adder, the worst case happens when inputs are 7FFF+0001. Since G will propagate from A_0 to S_15 which is the critical path.

Waveforms of test cases from layout• Worst case 7FFF+0001• A_0-A_15 B_0-B_15 Cout,S_0-S_15,

Waveforms of test cases from layout

• Delay from A_0 to S_15 is 8.946E-10S

Waveforms of test cases from layout• FFFF+0002• A_0-A_15 B_0-B_15 Cout,S_0-S_15,

Waveforms of test cases from layout• Other cases(1111 0000, 0011 0045, 11FF EDAB, 9782 1234, AABB 5432, 1543 78AB,• FFFF FFEE, 1AB2 F182, 1BCD 2525,2312+4567,1278+AC00,FFFF+FFFF,4444+7777,

1894+2636,CC53+D126• A_0-A_15 B_0-B_15 Cout,S_0-S_15

Final schematic of adder

Final LayoutArea: 37.4 μm×11.8μm

Maximum operating frequency for different VDD! from layout

0.65 0.7 0.75 0.8 0.85 0.9 0.95 1 1.05 1.1 1.150

0.2

0.4

0.6

0.8

1

1.2

Series1; T=100C; 0.24

T=100C; 0.4689

T=100C; 0.691

Series1; T=25C; 0.3795

T=25C; 0.759

T=25C; 1.13

Frequency VS. VDD

T=25CT=100C

VDD! (v)

Freq

uenc

y (G

Hz)

Power consumption at the maximum operating frequency at

different VDD

0.65 0.7 0.75 0.8 0.85 0.9 0.95 1 1.05 1.1 1.150

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

Series1; T=100C; 0.087154

T=100C; 0.27835

T=100C; 0.61588

Series1; T=25C; 0.12988

T=25C; 0.41989

T=25C; 0.931

Power VS. VDD

T=25CT=100C

VDD (v)

Pow

er (m

W)

Circuit netlist from layoutand

modified runtestadder16b_xxx.spSee attached files

Netlist name is : new_16_bit_adder

• Sizing• NMOS: L=50nm, W=90nm• PMOS: L=50nm, W=135nm• Temperature: 25°C

DRC Pass

LVS Pass