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

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Digital Integrated Circuits

Chapter 5 - Interconnections

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Contents

Introduction Resistance Capacitance RC delay Inductance Interconnection modeling Scaling effects on interconnection

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Introduction - 1

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 Trend toward higher integration levels partially driven by faster, denser, and more reliable on-chip than off- chip interconnects. Interconnect modeling: resistors, capacitors, and inductors.

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Introduction - 2

physical

Source: Rabaey

schematics

transmitters receivers

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Introduction - 3

Wire Models

All-inclusive model Capacitance-only

Source: Rabaey

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Introduction - 4

Source: Weste

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Introduction - 5

130 nm CMOS technology (Intel)

Transistor Via M1 M2 M3 M4 M5 M6 Isolation

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Resistance - 1

L L R R H W W ρ = =

฀

R฀ : sheet resistance R1 R2

W L H

I

Material property Height

Source: Rabaey

Defined by manufacturer Defined by designer (sometimes) Ohm’s law

/ I V R =

R I + V -

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Resistance - 2

Source: Rabaey

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Ex: Poly-resistor L W

Polysilicon

P substrate

Metal Metal

2

H

L R R R W = +

฀

R฀ : sheet resistance

H

R

: head resistance Top view

Resistance - 3

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Resistance - 4

Source: Rabaey

Example: Calculate the approximate resistance of a 1 μm-wide, 1 mm-long wire

• f (a) polysilicon; (b) aluminum. Use the data of the above table.

Sheet resistance values for a typical 0.25 μm CMOS process

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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

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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

Source: Kundert

Some circuit simulators: SPICE, PSPICE, HSPICE, Spectre, Smash, SPiceOpus,….

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Simulation 4.1

Use SpiceOpus to determine the (dc) I-V characteristic of a 1 kΩ resistor. resistortest * this is resistortest.cir file v0 1 0 dc 10V r1 1 0 1k .end r1 I V0 +

• Node 1

Node 0

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]

V=RI R I + V -

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Simulation 4.1

r1= 1 kΩ I V0 +

• Node 1

Node 0

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Exercise 4.1 Use SpiceOpus to determine the (dc) I-V0 transfer characteristic of the circuit given below.

r1= r2 =1 kΩ I V0 +

• r1

r2 r3 r3= 0.5 kΩ 1V ≥ V0≥ -1V