Báo cáo CMOS Circuit Design and Simulation

University of Science Silicon Design Solution Faculty of Electronics and Telecommunications A Division of eSilicon -----*------ Internship report CMOS Circuit Design and Simulation Reporter : Pham Ngoc Loi Student ID : 0720142 Tutors : Hoang Le Tan Dung Nguyen Truong Kha Nguyen Duc Thien Son Ho Chi Minh city - Jan 2011 Internship report 1 Comment of company and tutors ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ 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Internship report 2 Outline I. Introduction............................................................................................. 3 II. Content 1. Unix, C Shell, Perl ..................................................................... 4 1.1 What's Unix?...............................................................................4 1.2 Kernel .........................................................................................4 1.3 Shell..............................................................................................4 1.4 C shell..........................................................................................6 1.5 Perl........................................................................................9 2. CMOS Technology.................................................................... 10 3. Logic gate and simulation.......................................................... 14 1.1 INV gate......................................................................................15 1.2 INV_Z gate..................................................................................18 1.3 AND2 gate...................................................................................19 4. Memory design overview .......................................................... 20 5. Project: Design 4 to 16 Decoder................................................ 24 III. Conclusion .............................................................................................. 29 IV. Referential Documents .......................................................................... 30 Internship report 3 I. Introduction Circuit design is one of the most important level of CMOS IC design. The performance of CMOS ICs depend on the quality of circuit design. Circuit design includes designing and simulation. Simulating the design shows us the waveform of the circuit, delay, DC, AC characteristics. Moreover, we can vary parameters of circuit to check the operation in different conditions; from this variation, we can find out the best parameters for our design. I want to thank SDS company who gave me a chance to practice at company; I thank Mr. Ho Nam Tinh, Mr. Hoang Le Tan Dung, Mr. Nguyen Truong Kha and Mr. Nguyen Duc Thien Son for their help. I also want to thank my teachers in University of Science; specially, I want to thank Mr. Huynh Huu Thuan who always inquires after his students. Internship report 4 Unix, C shell, Perl 1.Unix: 1.1 What's Unix? • UNIX is a computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs. • Today’s UNIX system are splited into various branches, developed over time by AT&T as well as various commercial venders and non-profit organizations. • Today, in addition to certified UNIX systems, UNIX-like operating system such as Linux and BSD are commonly encountered. 1.2 Kernel • Kernel is the central component of the most operating system. Its responsibilities include managing the system’s resources (the communication between software and hardware components). • As a basic component of an operating system, a kernel provides the lowest-level abstraction layer for the resources (especially memory, processors and I/O devices) that application software must control to perform its function. 1.3 Shell • Shell acts as an interface between user and kernel. • As a UNIX user, you have a choice of shells available to you. These are the Bourne shell, the C shell, the Korn shell. 1.3.1 The directory structure • All the files in UNIX are grouped together in the directory structure. The file- system is arranged in a hierarchical structure, like an inverted tree. The top of the hierarchy is traditionally called root (written as a slash /). • Example of directory structure: Internship report 5 1.3.2 Basic command • Basic commands in UNIX are: mkdir, cd, cp, mv, rm, cat, touch, vi, ls, du, df, pwd, who, id, chmod, chown, chgrp, top, rlogin, rsh, ssh, ftp, sftp, clear, echo, setenv, tar, gzip, kill, history, man. o mkdir: create directory. o cd: change directory. o mv: move or rename a file or directory. o rm: remove file or directory. o cat: concatenate files and print on the standard output. o touch: create blank file. o vi: start text editor. o ls: list directory contents. o pwd: print name of current/working directory. o du: estimate file space usage. o df: report filesystem disk space usage. o who: show who is logged on. o id: print real and effective UIDs and GIDs. o chmod: change file access permissions. o chown: change file owner and group. o chgrp: change group ownership. o top: display Unix/Linux tasks. o rlogin: remote login. o rsh: remote shell. o ssh: OpenSSH SSH client (remote login program). o ftp: file transfer program. o sftp: secure file transfer program. o clear: clear the terminal screen. o echo: display a line of text. o setenv: add or change environment variable. o tar: the GNU version of the tar archiving utility. o gzip: compress or expand files. o kill: terminal a process. o history: the history command performs one of several operations. o related to recently-executed commands recorded in a history list. o man: format and display the on-line manual pages.
For more detail about above commands, from terminal, type: man 1.3.3 Vi editor • The VI editor is a screen-based editor used by many Unix users. • Some simple VI commands. Internship report 6 1.4 C shell 1.4.1 About C-shell • The C shell (csh) is a developed by Bill Joy for the BSD Unix system. It was originally derived from the 6th Edition Unix /bin/sh (which was the Thompson Shell), the predecessor of the Bourne Shell. Its syntax is modeled after the C programming language. The C shell added many feature improvements over the Bourne shell, such as aliases and command history. Today, the original C shell is not in wide use on Unix; it has been superseded by other shells such as the Tenex C shell (tcsh) based on the original C shell code, but adding filename completion and command line editing, comparable with the Korn Shell (ksh), and the GNU Bourne-Again shell (bash). • The C shell has the typical Unix shell structure: each line of input (or line of a script file) is interpreted as a separate command to execute, with backslashes "escaping" newlines where needed (so that multiple input lines can comprise a single command to be executed). Internship report 7 1.4.1 Invoking C-Shell • Each time you log in to UNIX, you're placed in an interactive shell referred to as your login shell. If your login shell is C shell, you can tell by its command-line prompt: the percent sign (%). The C shell prompt differs from the dollar sign prompt ($) of the Bourne shell to remind you that you're using the C shell. • If your login shell is not C shell, and C shell is available on your system, you can invoke it as an interactive shell from the command line. Even when you're already running the C shell, there will be times when you want to launch the C shell again, for example to run a shell script or to temporarily change the shell's options. To invoke the C shell interactively, use the following command: $ csh % 1.4.2 Built-in shell command Internship report 8 Internship report 9 1.4.3 Example a Shell program 1.4.Perl What's Perl? • Perl is the power and flexibility of high-level programming languages . • Contain control structures and operators similar to C programming. • Ability to write useful programs in a very short time. • Perl is freeware. Perl scrip • A Perl program consists of an ordinary text file containing a series of Perl commands. • Ex: #!/usr/local/bin/perl print “Hello world!\n”; Internship report 10 CMOS TECHNOLOGY The MOS Transistor  Switch model of NMOS Transistor  The NMOS Transistor Cross Section  n areas have been doped with donor ions (arsenic) of concentration ND - electrons are the majority carriers .  p areas have been doped with acceptor ions (boron) of concentration NA - holes are the majority carriers Internship report 11  Switch model of PMOS Transistor Gate oxide n+ Sourc Drain p substrate Bulk (Body) p+ stopper Field-Oxide (SiO2) n+ Polysilicon Gate L W Gate Source (of carriers) Drain (of carriers) | VGS | | VGS | > | VDD – | VT | | | VGS | < | VDD – |VT| | Open (off) (Gate = ‘1’) Closed (on) (Gate = ‘0’) Ron Internship report 12  Threshold voltage  The value of VGS where strong inversion occurs is called the threshold voltage, VT: VT = VT0 + γ(√|-2φF + VSB| - √|-2φF|) where o VT0 is the threshold voltage at VSB = 0 and is mostly a function of the manufacturing process. o VSB is the source-bulk voltage. o φF = -φTln(NA/ni) is the Fermi potential (φT = kT/q = 26mV at 300K is the thermal voltage; NA is the acceptor ion concentration; ni ≈ 1.5x1010 cm-3 at 300K is the intrinsic carrier concentration in pure silicon) . o γ = √(2qεsiNA)/Cox is the body-effect coefficient (impact of changes in VSB) (εsi=1.053x10-10F/m is the permittivity of silicon; Cox = εox/tox is the gate oxide capacitance with εox=3.5x10-11F/m).  Short channel effect  Behavior of short channel device mainly due to  Velocity saturation – the velocity of the carriers saturates due to scattering (collisions suffered by the carriers)  For an NMOS device with L of .25µm, only a couple of volts difference between D and S are needed to reach velocity saturation  Voltage-Current Relation: Velocity Saturation For short channel devices  Linear: When VDS ≤ VGS – VT ID = κ(VDS) k’n W/L [(VGS – VT)VDS – VDS2/2] Internship report 13 where κ(V) = 1/(1 + (V/ξcL)) is a measure of the degree of velocity saturation  Saturation: When VDS = VDSAT ≥ VGS – VT IDSat = κ(VDSAT) k’n W/L [(VGS – VT)VDSAT – VDSAT2/2]  Short Channel I-V Plot (NMOS) Internship report 14 Logic Gate and Simulation 1.1 INV gate Switching Threshold: Variation in device ratio: With : FF process, W = 0.12, L = 0.04, temp = 0, Vsup = 0.8V (W/L)p/(W/L)n Vtrip %VDD Delay 1 3.8627 0.416 -2.1p 2 3.8089 0.448 -2.77p 3 3.8295 0.476 -2.60p 4 4.0047 0.502 7.04p Process variation With : W = 0.12, L = 0.04, temp = 0, Vsup = 0.8V Process Vtrip %VDD Delay FF 3.8627 0.483 -2.1p FS 3.3275 0.416 -10p TT 4.1513 0.519 2.3p SF 4.9682 0.621 1.49p SS 4.9778 0.622 1.47p Internship report 15 Netlist - subckt: describe sub circuit of the circuit; in this command, we list input and output pins of the sub circuit; if sub circuit has parameters, we have to list their parameters in this command. - xi: describe instance circuit of a sub circuit. Internship report 16 Schematic Simulation and delay Internship report 17 1.2 INV_Z gate Schematic Simulation Internship report 18 1.3 AND2 gate Schematic Simulation Internship report 19 Memory design overview 1. The 1-bit Binary Adder: Truth table A B Cin Cout S carry status 0 0 0 0 0 kill 0 0 1 0 1 kill 0 1 0 0 1 propagate 0 1 1 1 0 propagate 1 0 0 0 1 propagate 1 0 1 1 0 propagate 1 1 0 1 0 generate 1 1 1 1 1 generate From the truth table above, we find out the output equations: G = A&B P = A ⊕ B K = !A & !B S = A ⊕ B ⊕ Cin Cout = A&B | A&Cin | B&Cin (majority function) Schematic of the 1-bit Binary Adder A B S Cout Cin schematic at logic gate level Internship report 20 Cout S Cin A B schematic at transistor level 2.Memory Cell: RWM: Random Access: SRAM( cache, register file), DRAM. Non- Random Access: FIFO/LIFO, Shift Register, CAM. NVRWM: EPROM, E2PROM, FLASH. ROM: Mask-programmed, Electrically-programmed (PROM). Internship report 21 1D Memory Architecture: Word 0 Word 1 Word 2 Word n-1 Word n-2 Storage Cell m bits S0 S1 S2 S3 Sn-2 Sn-1 Input/Output A0 A1 Ak-1 De co der Decoder reduces # of inputs k = log2 n Internship report 22 2D Memory Architecture: A0 Row Dec oder A1 Aj-1 Sense Amplifiers word line storage (RAM) cell Row Add ress Column Address Aj Aj+1 Ak-1 Read/Write Circuits Column Decoder 2k-j m2j Input/Output (m bits) amplifies bit line swing Internship report 23 SRAM circuit Static – SRAM and Dynamic – DRAM: Static – SRAM Dynamic – DRAM +data is stored as long as supply is applied +large cells (6 fets/cell) – so fewer bits/chip +fast – so used where speed is important (e.g., caches) +differential outputs (output BL and !BL) +use sense amps for performance +compatible with CMOS technology +periodic refresh required +small cells (1 to 3 fets/cell) – so more bits/chip +slower – so used for main memories +single ended output (output BL only) +need sense amps for correct operation +not typically compatible with CMOS technology Internship report 24 4 to 16 decoder Overview • Design 4 to 16 decoder, using basic logic gate: nand2, nor2, inv. • Simulate and view waveform. • Apply to: Design • State table: Word 0 Word 1 Word 2 Word n- 1 Word n- 2 Storage Cell m bits S0 S1 S2 S3 Sn-2 Sn-1 Input/Output A0 A1 Ak-1 De co der Internship report 25 • Use bool expression and De Morgan statement, we have: o Y0 = DCBA ... = ( )( )DCBA ++ . o Y1 = DCBA ... = ( )( )DCBA ++ . o Y2 = DCBA ... = ( )( )DCBA ++ . o ... Schematic • Y0 Internship report 26 • Y1 • Y2 • ..... • .... • 4 to 16 decoder Internship report 27 Internship report 28 Waveform Internship report 29 III.Conclusion So I think, in SDS, I learned a lot of useful things to supplement my knowledge in university and prepare for my future job. One more time, I want to thank to SDS and all people who give me useful help! Internship report 30 IV.Referential Documents Unix_C-shell_perl_training_document, Septemper 15, 2008 author Le Tu Duc. Slide Powerpoint SDS_100, January 25th 2008. SE_LAPs documents. Hspice_sa.pdf, version D-2010.03, March 2010