1 What this lecture is all about?  Introduction to digital integrated circuits.  CMOS devices and manufacturing technology. CMOS inverters and gates. Propagation delay, noise margins, and power dissipation. Sequential circuits. Arithmetic, interconnect, and memories. Programmable logic arrays. Design methodologies.  What will you learn?  Understanding, designing, and optimizing digital circuits with respect to different quality metrics: cost, speed, power dissipation, and reliability

2 Digital Integrated Circuits  Introduction: Issues in digital design  The CMOS inverter  Combinational logic structures  Sequential logic gates  Design methodologies  Interconnect: R, L and C  Timing  Arithmetic building blocks  Memories and array structures

3 Introduction  Why is designing digital ICs different today than it was before?  Will it change in future?

4 The First Computer

5 ENIAC - The first electronic computer (1946)

6 The Transistor Revolution First transistor Bell Labs, 1948

7 The First Integrated Circuits Bipolar logic 1960’s ECL 3-input Gate Motorola 1966

8 Intel 4004 Micro-Processor Intel 4004 Micro-Processor transistors 1 MHz operation

9 Intel Pentium (IV) microprocessor

10 Why VLSI?  Integration improves the design:  lower parasitics = higher speed;  lower power;  physically smaller.  Integration reduces manufacturing cost- (almost) no manual assembly.

11 VLSI and you  Microprocessors:  personal computers;  microcontrollers.  DRAM/SRAM.  Special-purpose processors.

12 Moore’s Law lIn 1965, Gordon Moore noted that the number of transistors on a chip doubled every 18 to 24 months. lHe made a prediction that semiconductor technology will double its effectiveness every 18 months

13 Moore’s Law Electronics, April 19, 1965.

14 Evolution in Complexity

15 Transistor Counts 1,000, ,000 10,000 1, i386 i486 Pentium ® Pentium ® Pro K 1 Billion Transistors Source: Intel Projected Pentium ® II Pentium ® III Courtesy, Intel

16 Moore’s law in Microprocessors Pentium® proc P Year Transistors (MT) 2X growth in 1.96 years! Transistors on Lead Microprocessors double every 2 years Courtesy, Intel

17 Die Size Growth Pentium ® proc P Year Die size (mm) ~7% growth per year ~2X growth in 10 years Die size grows by 14% to satisfy Moore’s Law Courtesy, Intel

18 Frequency P6 Pentium ® proc Year Frequency (Mhz) Lead Microprocessors frequency doubles every 2 years Doubles every 2 years Courtesy, Intel

19 Power Dissipation P6 Pentium ® proc Year Power (Watts) Lead Microprocessors power continues to increase Courtesy, Intel

20 Power will be a major problem 5KW 18KW 1.5KW 500W Pentium® proc Year Power (Watts) Power delivery and dissipation will be prohibitive Courtesy, Intel

21 Power density Pentium® proc P Year Power Density (W/cm2) Hot Plate Nuclear Reactor Rocket Nozzle Power density too high to keep junctions at low temp Courtesy, Intel

22 Not Only Microprocessors Digital Cellular Market (Phones Shipped) Units 48M 86M 162M 260M 435M Analog Baseband Digital Baseband (DSP + MCU ) Power Management Small Signal RF Power RF (data from Texas Instruments) Cell Phone

23 Challenges in Digital Design “Microscopic Problems” Ultra-high speed design Interconnect Noise, Crosstalk Reliability, Manufacturability Power Dissipation Clock distribution. Everything Looks a Little Different “Macroscopic Issues” Time-to-Market Millions of Gates High-Level Abstractions Reuse & IP: Portability Predictability etc. …and There’s a Lot of Them!  DSM  1/DSM ?

24 Productivity Trends ,000 10, ,000 1,000,000 10,000, ,000 10, ,000 1,000,000 10,000, ,000,000 Logic Tr./Chip Tr./Staff Month. x x x x x x x 21%/Yr. compound Productivity growth rate x 58%/Yr. compounded Complexity growth rate 10,000 1, Logic Transistor per Chip (M) ,000 10, ,000 Productivity (K) Trans./Staff - Mo. Source: Sematech Complexity outpaces design productivity Complexity Courtesy, ITRS Roadmap

25 Why Scaling?  Technology shrinks by 0.7/generation  With every generation can integrate 2x more functions per chip; chip cost does not increase significantly  Cost of a function decreases by 2x  But …  How to design chips with more and more functions?  Design engineering population does not double every two years…  Hence, a need for more efficient design methods  Exploit different levels of abstraction

26 Challenges in VLSI design  Multiple levels of abstraction: transistors to CPUs.  Multiple and conflicting constraints: low cost and high performance are often at odds.  Short design time: Late products are often irrelevant.

27 Dealing with complexity  Divide-and-conquer: limit the number of components you deal with at any one time.  Group several components into larger components:  transistors form gates;  gates form functional units;  functional units form processing elements;  etc.

28 Hierarchical name  Interior view of a component:  components and wires that make it up.  Exterior view of a component = type:  body;  pins. Full adder a b cin sum cout

29 Instantiating component types  Each instance has its own name:  add1 (type full adder)  add2 (type full adder).  Each instance is a separate copy of the type: Add1(Full adder) a b cin sum cout Add2(Full adder) a b cin sum Add1.a Add2.a

30 Net lists and component lists  Net list: net1: top.in1 in1.in net2: i1.out xxx.B topin1: top.n1 xxx.xin1 topin2: top.n2 xxx.xin2 botin1: top.n3 xxx.xin3 net3: xxx.out i2.in outnet: i2.out top.out  Component list: top: in1=net1 n1=topin1 n2=topin2 n3=topine out=outnet i1: in=net1 out=net2 xxx: xin1=topin1 xin2=topin2 xin3=botin1 B=net2 out=net3 i2: in=net3 out=outnet

31 Component hierarchy top i1xxxi2

32 Hierarchical names  Typical hierarchical name:  top/i1.foo component pin

33 Design Abstraction Levels n+ S G D + DEVICE CIRCUIT GATE MODULE SYSTEM

34 Layout and its abstractions  Layout for dynamic latch:

35 Stick diagram

36 Transistor schematic

37 Mixed schematic inverter

38 Levels of abstraction  Specification: function, cost, etc.  Architecture: large blocks.  Logic: gates + registers.  Circuits: transistor sizes for speed, power.  Layout: determines parasitics.

39 Circuit abstraction  Continuous voltages and time:

40 Digital abstraction  Discrete levels, discrete time:

41 Register-transfer abstraction  Abstract components, abstract data types:

42 Top-down vs. bottom-up design  Top-down design adds functional detail.  Create lower levels of abstraction from upper levels.  Bottom-up design creates abstractions from low-level behavior.  Good design needs both top-down and bottom-up efforts.

43 Design abstractions specification behavior register- transfer logic circuit layout English Executable program Sequential machines Logic gates transistors rectangles Throughput, design time Function units, clock cycles Literals, logic depth nanoseconds microns functioncost

44 Design Metrics  How to evaluate performance of a digital circuit (gate, block, …)?  Cost  Reliability  Scalability  Speed (delay, operating frequency)  Power dissipation  Energy to perform a function

45 Cost factors in ICs  For large-volume ICs:  packaging is largest cost;  testing is second-largest cost.  For low-volume ICs, design costs may swamp all manufacturing costs.

46 Cost of Integrated Circuits  NRE (non-recurrent engineering) costs  design time and effort, mask generation  one-time cost factor  Recurrent costs  silicon processing, packaging, test  proportional to volume  proportional to chip area

47 NRE Cost is Increasing

48 Die Cost Single die Wafer From Going up to 12” (30cm)

49 Cost per Transistor cost: ¢-per-transistor Fabrication capital cost per transistor (Moore’s law)

50 Yield

51 Defects  is approximately 3

52 Some Examples (1994) ChipMetal layers Line width Wafer cost Def./ cm 2 Area mm 2 Dies/ wafer YieldDie cost 386DX 20.90$ %$4 486 DX $ %$12 Power PC $ %$53 HP PA $ %$73 DEC Alpha 30.70$ %$149 Super Sparc 30.70$ %$272 Pentium 30.80$ %$417

53 Reliability― Noise in Digital Integrated Circuits i(t) Inductive coupling Capacitive couplingPower and ground noise v (t) V DD

54 DC Operation Voltage Transfer Characteristic V(x) V(y) V OH V OL V M V OH V OL f V(y)=V(x) Switching Threshold Nominal Voltage Levels VOH = f(VOL) VOL = f(VOH) VM = f(VM)

55 Mapping between analog and digital signals V IL V IH V in Slope = -1 V OL V OH V out “0” V OL V IL V IH V OH Undefined Region “1”

56 Definition of Noise Margins Noise margin high Noise margin low V IH V IL Undefined Region "1" "0" V OH V OL NM H L Gate Output Gate Input

57 Noise Budget  Allocates gross noise margin to expected sources of noise  Sources: supply noise, cross talk, interference, offset  Differentiate between fixed and proportional noise sources

58 Key Reliability Properties  Absolute noise margin values are deceptive  a floating node is more easily disturbed than a node driven by a low impedance (in terms of voltage)  Noise immunity is the more important metric – the capability to suppress noise sources  Key metrics: Noise transfer functions, Output impedance of the driver and input impedance of the receiver;

59 Regenerative Property Regenerative Non-Regenerative

60 Regenerative Property A chain of inverters v 0 v 1 v 2 v 3 v 4 v 5 v 6 Simulated response

61 Fan-in and Fan-out N Fan-out N Fan-in M M

62 The Ideal Gate R i =  R o = 0 Fanout =  NM H = NM L = V DD /2 g =  V in V out

63 An Old-time Inverter NM H V in (V) V out (V) NM L V M

64 Delay Definitions

65 Ring Oscillator T = 2  t p  N

66 A First-Order RC Network v out v in C R t p = ln (2)  = 0.69 RC Important model – matches delay of inverter

67 Power Dissipation Instantaneous power: p(t) = v(t)i(t) = V supply i(t) Peak power: P peak = V supply i peak Average power:

68 Energy and Energy-Delay Power-Delay Product (PDP) = E = Energy per operation = P av  t p Energy-Delay Product (EDP) = quality metric of gate = E  t p

69 A First-Order RC Network v out v in CLCL R

70 Summary  Digital integrated circuits have come a long way and still have quite some potential left for the coming decades  Some interesting challenges ahead  Getting a clear perspective on the challenges and potential solutions is the purpose of this book  Understanding the design metrics that govern digital design is crucial  Cost, reliability, speed, power and energy dissipation