Chapter 3b Static Noise Analysis - PowerPoint PPT Presentation

Loading...

PPT – Chapter 3b Static Noise Analysis PowerPoint presentation | free to download - id: 844f68-MTM0N



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

Chapter 3b Static Noise Analysis

Description:

Chapter 3b Static Noise Analysis Aggressor net Cx Victim net Prof. Lei He Electrical Engineering Department University of California, Los Angeles URL: eda.ee.ucla.edu – PowerPoint PPT presentation

Number of Views:53
Avg rating:3.0/5.0
Slides: 39
Provided by: gongfang
Learn more at: http://eda.ee.ucla.edu
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: Chapter 3b Static Noise Analysis


1
Chapter 3b Static Noise Analysis
  • Prof. Lei He
  • Electrical Engineering Department
  • University of California, Los Angeles
  • URL eda.ee.ucla.edu
  • Email lhe_at_ee.ucla.edu

2
Outline
  • Introduction and Motivation
  • Noise Models
  • RC Model
  • J. Cong, Z. Pan and P. V. Srinivas, "Improved
    Crosstalk Modeling for Noise Constrained
    Interconnect Optimization", ASPDAC 2001
  • Worst case noise for RC
  • Lauren Hui Chen, Malgorzata Marek-Sadowska
    Aggressor alignment for worst-case coupling
    noise. ISPD 2000 48-54
  • Worst case noise for RLC
  • Jun Chen and Lei He, "Worst-Case Crosstalk Noise
    for Non-Switching Victims in High-speed Buses",
    TCAD, Volume 24, Issue 8, Aug. 2005, Pages 1275
    - 1283

3
Introduction
  • Coupling Capacitance Dominates
  • Signal delay
  • Crosstalk noise
  • What is Crosstalk noise?
  • Capacitive coupling between an aggressor net and
    a victim net leads to coupled noise
  • Aggressor net switches states source of noise
    for victim net
  • Victim net maintains present state affected by
    coupled noise from aggressor net

4
Noise Models
  • RC model
  • J. Cong, Z. Pan and P. V. Srinivas, "Improved
    Crosstalk Modeling for Noise Constrained
    Interconnect Optimization", ASPDAC 2001
  • Worst case noise for RC
  • Lauren Hui Chen, Malgorzata Marek-Sadowska
    Aggressor alignment for worst-case coupling
    noise. ISPD 2000 48-54
  • Worst case noise for RLC
  • Jun Chen and Lei He, "Worst-Case Crosstalk Noise
    for Non-Switching Victims in High-speed Buses",
    TCAD, Volume 24, Issue 8, Aug. 2005, Pages 1275
    - 1283

5
Aggressor / Victim Network
  • Assuming idle victim net
  • Ls Interconnect length before coupling
  • Lc Interconnect length of coupling
  • Le Interconnect length after coupling
  • Aggressor has clock slew tr

6
2- p Model
  • Victim net is modeled as 2-p -RC circuits
  • Rd Victim drive resistance
  • Cx is assumed to be in middle of Lc

victim / aggressor coupling capacitance
7
2- p Model Parameters
8
Analytical Solution
9
Analytical Solution part 2
  • s-domain output voltage
  • Transform function H(s)

10
Analytical Solution part 3
  • Aggressor input signal
  • Output voltage

11
Simplification of Closed Form Solution
  • Closed form solution complicated
  • Non-intuitive
  • Noise peak amplitude, noise width?
  • Dominant-pole approximation method

12
Dominant-Pole Simplification
13
Intuition of Dominant Pole Simplification
  • vout rises until tr and decays after
  • vmax evaluated at tr

14
Extension to RC Trees
  • Similar to previous model with addition of lumped
    capacitances
  • Extended to a victim net in general RC tree
    structure

15
Results
  • Average errors of 4 comparing to HSPICE in peak
    noise and noise width.
  • Devgan model 589
  • Vittal model 9
  • 95 of nets have errors less than 10

16
Spice Comparison
  • peak noise noise width

17
Effect of Aggressor Location
  • As aggressor is moved close to receiver, peak
    noise is increased

Ls varies from 0 to 1mm Lc has length of 1mm Le
varies from 1mm to 0
18
Optimization Rules
  • Rule 1
  • If RsC1 lt ReCL
  • Sizing up victim driver will reduce peak noise
  • If RsC1 gt ReCL and tr ltlt tv
  • Driver sizing will not reduce peak noise
  • Rule 2
  • Noise-sensitive victims should avoid
    near-receiver coupling

19
Optimization Rules part 2
  • Rule 3
  • Preferred position for shield insertion is near a
    noise sensitive receiver
  • Rule 4
  • Wire spacing is an effective way to reduce noise
  • Rule 5
  • Noise amplitude-width product has lower bound
  • And upper bound

20
Noise Models
  • Devgans model
  • Anirudh Devgan, "Efficient Coupled Noise
    Estimation for On-chip Interconnects", ICCAD,
    1997.
  • 2-Pi model
  • J. Cong, Z. Pan and P. V. Srinivas, "Improved
    Crosstalk Modeling for Noise Constrained
    Interconnect Optimization", ASPDAC 2001
  • Worst case noise for RC
  • Lauren Hui Chen, Malgorzata Marek-Sadowska
    Aggressor alignment for worst-case coupling
    noise. ISPD 2000 48-54
  • Shield Insertion and Net Ordering (SINO)
  • L. He and K. M. Lepak, "Simultaneous shield
    insertion and net ordering for capacitive and
    inductive coupling minimization", ISPD 2000
  • Worst case noise for RLC
  • Jun Chen and Lei He, "Worst-Case Crosstalk Noise
    for Non-Switching Victims in High-speed Buses",
    TCAD, Volume 24, Issue 8, Aug. 2005, Pages 1275
    - 1283

21
Worst Case Noise Model
  • Consider multiple-aggressors situation
  • Each aggressor (A1, , A5) has its switching
    signal.
  • Each switching aggressor will result in a
    coupling noise on victim at variable arrival
    times.

22
Worst Case Noise Model
  • To consider Worst Case Noise (WCN)
  • Make alignment of aggressor inputs (change
    arrival time)
  • The coupling noise at victim output can occur at
    the same time.
  • Aggressor Alignment Problem Formulation
  • Find the relative relationships among arrival
    times for all aggressor inputs such that all
    individual peak noises are aligned, assuming all
    the other conditions are fixed.

23
WCN Superposition
  • Consider two aggressors (V1 and V2) case
  • N1 when V1 is switching, V2 is quiet
  • N2 when V2 is switching, V1 is quiet

Individual noise waveforms
24
WCN Superposition
  • To consider WCN, the aggressor alignment is
    performed
  • Change the arrival time of V2
  • Two noise signals can occur at the same time

25
WCN Analysis strategies
  • Four WCN analysis strategies based on aggressor
    alignment
  • Explicit Aggressor Alignment (AS Aligned
    switching)
  • Noise output is obtained by aligning switching of
    all aggressors. The largest amplitude is WCN.
  • No Aggressor Alignment (SS simultaneous
    switching)
  • Simultaneous switching of all aggressors.
  • Implicit Aggressor Alignment (SP Superposition)
  • Each noise output is obtained with only one
    aggressor switching
  • Total peak noise is the summation over all
    individual peak noise.
  • Extension of Implicit Aggressor Alignment
  • Each noise output is obtained with only one
    aggressor switching
  • back-annotates use output noise to determine
    the aggressor input skews, and estimate the
    coupling stage again.

26
Noise Models
  • Devgans model
  • Anirudh Devgan, "Efficient Coupled Noise
    Estimation for On-chip Interconnects", ICCAD,
    1997.
  • 2-Pi model
  • J. Cong, Z. Pan and P. V. Srinivas, "Improved
    Crosstalk Modeling for Noise Constrained
    Interconnect Optimization", ASPDAC 2001
  • Worst case noise for RC
  • Lauren Hui Chen, Malgorzata Marek-Sadowska
    Aggressor alignment for worst-case coupling
    noise. ISPD 2000 48-54
  • Shield Insertion and Net Ordering (SINO)
  • L. He and K. M. Lepak, "Simultaneous shield
    insertion and net ordering for capacitive and
    inductive coupling minimization", ISPD 2000
  • Worst case noise for RLC
  • Jun Chen and Lei He, "Worst-Case Crosstalk Noise
    for Non-Switching Victims in High-speed Buses",
    TCAD, Volume 24, Issue 8, Aug. 2005, Pages 1275
    - 1283

27
Problem Formulation
  • Assume coplanar parallel interconnect structures
    (termed a placement),

Vdd
Gnd
s1
s2
s3
s4
  • Cx coupling has been considered, but Lx coupling
    can not be neglected.
  • Simultaneous shield insertion and net ordering
    (SINO)
  • Net ordering eliminates Cx noise
  • Shield insertion removes Lx noise

28
Characteristics of Lx Coupling
of Shields Noise ( of Vdd)
0 (a) 0.71V (55)
2 (b) 0.38V (29)
5 (c) 0.17V (13)
(18 bit bus structure from He et. al., CICC 1999)
(a)
(b)
(c)
  • Lx coupling between non-adjacent nets is
    non-trivial
  • Shielding is effective to reduce Lx coupling

29
Net Sensitivity
  • Two nets are considered sensitive if a switching
    event on signal s1 happens during a sample time
    window for s2

error occurs
Signal levels (V)
aggressor
VIH
victim1
victim2
time
Sampling window
no error occurs
30
SINO/NF Problem Formulation
  • Given An initial placement P
  • Find A new placement P via simultaneous shield
    insertion and net ordering such that
  • P is capacitive noise free
  • Sensitive nets are not adjacent to each other
  • P is inductive noise free
  • Sensitive nets do not share a block
  • P has minimal area

31
SINO/NB Problem Formulation
  • Given An initial placement P
  • Find A new placement P via simultaneous shield
    insertion and net ordering such that
  • P is capacitive noise free
  • All nets in P have inductive noise less than a
    given value
  • P has minimal area

32
Noise Models
  • 2-Pi model
  • J. Cong, Z. Pan and P. V. Srinivas, "Improved
    Crosstalk Modeling for Noise Constrained
    Interconnect Optimization", ASPDAC 2001
  • Worst case noise for RC
  • Lauren Hui Chen, Malgorzata Marek-Sadowska
    Aggressor alignment for worst-case coupling
    noise. ISPD 2000 48-54
  • Shield Insertion and Net Ordering (SINO)
  • L. He and K. M. Lepak, "Simultaneous shield
    insertion and net ordering for capacitive and
    inductive coupling minimization", ISPD 2000
  • Worst case noise for RLC
  • Jun Chen and Lei He, "Worst-Case Crosstalk Noise
    for Non-Switching Victims in High-speed Buses",
    TCAD, Volume 24, Issue 8, Aug. 2005, Pages 1275
    - 1283

33
Worst Case Noise (WCN) for RLC tree
  • Problem Formulation
  • Given a non-switching victim and multiple
    aggressors in a pre-routed interconnect structure
  • Object find switching patterns and switching
    times for all aggressors such that the noise in
    the victim has maximal amplitude.
  • Recall basic WCN analyses for RC model
  • SS Simultaneous switching
  • SP Superposition
  • AS Aligned switching

How to extend WCN analysis to the RCL model?
34
WCN under the RCL model
  • Shielding
  • Dedicated shields can reduce crosstalk noise.
  • Assume there are shields at both edges of the bus
    structure.

Vdd
Gnd
s1
s2
s3
s4
35
WCN under the RCL model
  • Switching Pattern
  • Waveform can have resonance due to inductance
    under RCL model
  • Resonance leads to multiple noise peaks with
    opposite polarities.
  • WCN may happen when aggressors switch in the same
    or different direction.

V quiet victim q q quiet wire a -
aggressor S - shield
36
WCN under the RCL model
  • Routing Direction
  • Same direction or Opposite direction
  • Consider two routing directions
  • One is aggressor and the other is victim
  • Same direction routing leads to smaller crosstalk
    noise
  • Noise difference results from different current
    flow, and different loop inductance.

37
WCN analysis under RLC model
  • Extension to Existing Algorithm for RC
  • Simultaneous Switching (SS)
  • All aggressors switch simultaneously in the same
    direction
  • WCN is the maximum noise on the victim
  • Superposition (SP)
  • Find maximum noise peak for each aggressor when
    only this aggressor switches.
  • WCN is the summation of amplitudes of all such
    peaks.

38
WCN analysis under RLC model
  • AS (Aligned Switching)
  • Find individual noise with only one aggressor
    switching
  • Switch multiple aggressors to find the maximum
    noise
  • PP alignment
  • align the maximum positive peaks of individual
    noises
  • all aggressors switch in the same direction
  • NN alignment
  • align the maximum negative peaks of individual
    noises
  • all aggressors switch in the same direction
  • PN alignment
  • align the peaks of maximum amplitude
  • Aggressors have switching directions that all the
    aligned peaks have the same polarity.
  • WCN is the maximum noise among the above
    simulations.
About PowerShow.com