Skinny Trace Compensation Methodology for High

Speed Serial Interface

11

Minhong Mi, Steve Taliaferro, Rajen Murugan, Daniel de Araujo

May 14th, 2012

SPI 2012

Agenda

• Skinny Trace Compensation

– Description

– Computation

– Implementation

– HDMI Channel

22

– HDMI Channel

– PCB Layout and Extraction

– Improvements

– Conclusion

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Skinny Trace Compensation Technique

x

Z0Z

0

Z1=kZ0

CL

33

*

0

0

0 )/(

))(/(

LC

kZ

vx

kZvxZ

+

=

Z0: Characteristic impedance of regular

transmission line

v: Unloaded trace propagation constant

k=Zl/Z0: Ratio of impedance for the skinny and the

regular segments

CL: Capacitance of the load

*Johnson, H. and Graham, M., High Speed Signal Propagation—Advanced Black Magic, Prentice-Hall (New York,

2003), pp. 300-302.

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Skinny Trace Implementation

44

Typical Layout transition Improved Layout transition

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HDMI Channel

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Pre-layout Simulation Setup

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Simulated Eye Diagram (pre-layout)

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PCB Layout

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Package and PCB Model Extraction

99

Package

PCB

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Post-layout Circuit Simulation Setup

Package

Cdie

Cesd

connector

Driver

1010

�Detailed spice netlist was used to represent the driver

�Pseudo-random bit sources with different seeds were used as inputs to the driver circuits

PCB

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Simulated Eye diagram (post-layout)

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Measurement

(Without Skinny Trace Compensation)

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Measurement

(With Skinny Trace Compensation)

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Model / Correlation: Before / After

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Conclusions

• Skinny Trace Compensation is an effective yet

simple technique to address excess capacitive

impedance in high speed channels.

• System level methodology for a high speed

serial interface (HDMI) interface on a high-

speed/low power mobile microprocessor SOIC

1515

speed/low power mobile microprocessor SOIC

design is presented.

• Excellent correlation between simulated and

measured results were obtained.

SPI 2012