Digital Integrated Circuits Chapter 5 - Interconnections EEL7312 - PowerPoint PPT Presentation

Digital Integrated Circuits Chapter 5 - Interconnections EEL7312 – INE5442 1 Digital Integrated Circuits

Contents � Introduction � Resistance � Capacitance � RC delay � Inductance � Interconnection modeling � Scaling effects on interconnection EEL7312 – INE5442 2 Digital Integrated Circuits

Introduction - 1 Trend toward higher integration levels partially driven by faster, denser, and more reliable on-chip than off- chip interconnects. Why are on-chip interconnects important? As technology scales to deep submicron: � Increased contribution to propagation delay � Increased contribution on energy dissipation � Introduces extra noise, affects reliability Interconnect modeling: resistors, capacitors, and inductors. EEL7312 – INE5442 3 Digital Integrated Circuits

4 physical Digital Integrated Circuits EEL7312 – INE5442 receivers Introduction - 2 schematics Source: Rabaey transmitters

Introduction - 3 Wire Models Capacitance-only All-inclusive model Source: Rabaey EEL7312 – INE5442 5 Digital Integrated Circuits

6 Digital Integrated Circuits EEL7312 – INE5442 Introduction - 4 Source: Weste

Introduction - 5 130 nm CMOS technology (Intel) M6 M5 Via M4 M3 M2 M1 Isolation Transistor EEL7312 – INE5442 7 Digital Integrated Circuits

Resistance - 1 Material ρ L L Defined by Defined by = = property R R Ohm’s law designer ฀ manufacturer H W W (sometimes) Height + V - I R ฀ : sheet resistance R = I V R / L R 1 R 2 H W I Source: Rabaey EEL7312 – INE5442 8 Digital Integrated Circuits

9 Digital Integrated Circuits EEL7312 – INE5442 Resistance - 2 Source: Rabaey

Resistance - 3 Top view W L Metal Metal Polysilicon L = + P substrate R R 2 R ฀ H W Ex: Poly-resistor R ฀ : sheet resistance R : head resistance H EEL7312 – INE5442 10 Digital Integrated Circuits

Resistance - 4 Sheet resistance values for a typical 0.25 μ m CMOS process Example: Calculate the approximate resistance of a 1 μ m-wide, 1 mm-long wire of (a) polysilicon; (b) aluminum. Use the data of the above table. Source: Rabaey EEL7312 – INE5442 11 Digital Integrated Circuits

Circuit Simulation - 1 Why using circuit simulators? Designs can be quickly evaluated without (sometimes very expensive) fabrication. After design has been evaluated you can prototype it before mass production. A circuit simulator computes the response of the circuit to a particular stimulus. The simulator formulates the circuit equations and then numerically solves them. Types of analyses: � DC/DC sweep: Both stimuli and responses do not vary with time � Transient: Responses vary with time � AC/Noise: also called small-signal analysis, it computes the sinusoidal steady-state response Source: Kundert EEL7312 – INE5442 12 Digital Integrated Circuits

Circuit Simulation - 2 What are the input data? Device Type (R, C, L, current sources, voltage sources, diodes, transistors) Device models/parameters/ dimensions How devices are connected Some circuit simulators: SPICE, PSPICE, HSPICE, Spectre, Smash, SPiceOpus,…. Source: Kundert EEL7312 – INE5442 13 Digital Integrated Circuits

Simulation 4.1 Use SpiceOpus to determine the (dc) I-V characteristic of a 1 k Ω resistor. + V - Node 1 resistortest I * this is resistortest.cir file I R V 0 + v0 1 0 dc 10V r 1 - V=RI r1 1 0 1k Node 0 .end SpiceOpus (c) 1 -> source resistortest.cir SpiceOpus (c) 2 -> dc v0 -1V 1V 2mV SpiceOpus (c) 3 -> setplot dc1 SpiceOpus (c) 4 -> plot i(v0) xlabel v(1) ylabel current[A] SpiceOpus (c) 5 -> plot -1000*i(v0) xlabel v(1) ylabel current[mA] EEL7312 – INE5442 14 Digital Integrated Circuits

15 Digital Integrated Circuits EEL7312 – INE5442 Simulation 4.1 r 1 = 1 k Ω Node 1 Node 0 I V 0 + -

Exercise 4.1 Use SpiceOpus to determine the (dc) I-V 0 transfer characteristic of the circuit given below. r 3 I V 0 + r 1 r 2 - r 1 = r 2 =1 k Ω r 3 = 0.5 k Ω 1V ≥ V 0 ≥ - 1V EEL7312 – INE5442 16 Digital Integrated Circuits