Minimizing Simultaneous Switching Noise SSN using Modified OddEven Bus Invert Method

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Minimizing Simultaneous Switching Noise (SSN)
using Modified Odd/Even Bus Invert Method
Electronic Design, Test and Applications, 2006.
DELTA 2006. Third IEEE International Workshop

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Outline

• Abstract
• Introduction
• Theory
• Propose Coding Scheme
• Simulation Results
• Conclusions

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Abstract

• In high speed digital circuits, the inductive
  effect is more dominant compared to capacitive
  effect.
• This paper reduces the simultaneous switching
  activity, thereby improving the signal integrity.
• Simultaneous Switching Noise (SSN) is reduced by
  28 compared to data transmitted unencoded.
• The proposed Codec has been designed that power
  overhead is 3.3.

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Introduction

• The effect of inductive crosstalk in IC packaging
  is becoming a significant bottleneck in inter
  chip communications.
• International Roadmap for Semiconductors (ITRS)
  has predicted that IC performance is continuing
  to be doubled every 18 months whereas the package
  performance is doubling over the next decade 1.
• As we approach DSM technology, the spacing
  between interconnects becomes less, which leads
  to crosstalk, and thereby deteriorating the
  signal integrity 7.

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Crosstalk noise

• Mutual inductance Lm induces current from an
  aggressor line onto a quiet line by means of
  magnetic field thereby degrading the signal
  integrity 3.
• A crosstalk may be induced in the voltage of a
  pin i in which the signal is static, by the
  adjacent pins in which the signal is varying 5.

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Equivalent circuit model for two wire bus
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Odd Mode Even Mode
Assume L11 L22 L0
LoddL11-L22
LevenL11L22
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Propose Coding Scheme

• Let the input to the proposed coding scheme at
  time (K1) be Ak1 and let Ek1 be the output at
  that time.
• Calculate the number of SST of Ak1 at odd
  position and denote it by OST(Odd Simultaneous
  Transitions)
• Calculate the number of SST of Ak1 at even
  position and denote it by EST(Even Simultaneous
  Transitions)

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Propose Coding Scheme
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Example 1

• Let the present data on the bus be Ak1
  11111111.
• The number of OST is 4 EST is 3. Since OST is
  greater than EST, hence flip the odd positioned
  bits append with 01.
• Thus the data to be transmitted after encoding is
  Ek1 0101010101.
• Thus the Simultaneous transition is reduced from
  7 to 0 which reduces the SSN.

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Example 2

• Let the present data on the bus be Ak1
  10101010.
• The number of OST EST is 0. Since OST is equal
  to EST, the data is transmitted with encoding
  appending 10.
• Thus the data to be transmitted after encoding is
  Ek1 1010101010.
• Thus the best case is transmitted as it is
  without increasing the crosstalk.

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Hardware implementation of the proposed Encoder
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Hardware implementation of the decoder
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Comparison of Crosstalk Noise
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Percent Power Overhead
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Layout of the proposed codec
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Conclusion

• The inductive effect in IC packaging is well
  pronounced in high speed digital circuit which
  degrades the signal integrity.
• This paper proposed a Modified Odd/Even Bus
  Invert coding and it has been found that SSN or
  glitching is reduced by 28.