2Contents Summary Design Optimization & Changes Waveforms of test cases Schematic & Layoutmaximum operating frequency VS. VDDPower consumption at the maximum operating frequency VS. VDDNetlistDRC,LVS results
3SummaryThe 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.
4Summary Structure of 16 bit Sklansky Adder (Black square is dot operatorGrey square is empty dot operatorWhite triangle is buffer)
5Reference ListD.Harris, “ A Taxonomy of Parallel Prefix Networks, Signals ”, Systems and Computers, Conference Record of the Thirty-Seventh Asilomar Conference on, 2, Vol.2,2003J. Sklansky, “Conditional-sum addition logic,” IRE Trans. Electronic Computers, vol. EC-9, pp , June 1960.J M. Rabaey, A. Chandrakasan, B. Nikolic, “ Digital Integrated Circuits-A Design Perspective (Second Edition)”, Prentice Hall, 2003Wu,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, 1-4Mason, 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
6Design Optimization and changes Sizing the gate to minimum size (90nm) reduces powerBy using bubble shifting, we save totally 28 inverters, and 4 inverters on the critical pathAdding the buffer can effectively reduce delay. Setting stage=1, fanout=4Minimizing each block to reduce areaCombining VDDs of different devices to reduce area
7Design Optimization and changes Combining Nwell and Pwell of different devices to simplify the layoutUsing fewer metal layers (2 layers) to reduce complexity and capacitanceChanges: Fixing some flaws (body not connected to ground) in schematic
8Waveforms of test cases Worst case: For Sklansky adder, the worst case happens when inputs are 7FFF Since G will propagate from A_0 to S_15 which is the critical path.
9Waveforms of test cases from layout Worst case 7FFF+0001A_0-A_ B_0-B_ Cout,S_0-S_15,
10Waveforms of test cases from layout Delay from A_0 to S_15 is 8.946E-10S
11Waveforms of test cases from layout FFFF+0002A_0-A_ B_0-B_ Cout,S_0-S_15,
12Waveforms of test cases from layout Other cases( , , 11FF EDAB, , AABB 5432, AB,FFFF FFEE, 1AB2 F182, 1BCD 2525, ,1278+AC00,FFFF+FFFF, , ,CC53+D126A_0-A_ B_0-B_ Cout,S_0-S_15
15Maximum operating frequency for different VDD! from layout
16Power consumption at the maximum operating frequency at different VDD
17Circuit netlist from layout and modified runtestadder16b_xxx Circuit netlist from layout and modified runtestadder16b_xxx.sp See attached files Netlist name is : new_16_bit_adderSizingNMOS: L=50nm, W=90nmPMOS: L=50nm, W=135nmTemperature: 25°C