当前位置：文档库 › [Training PPT]Signal Integrity [Compatibility Mode]

[Training PPT]Signal Integrity [Compatibility Mode]

Signal Integrity and High Speed Serial Link PCB Layout Guideline
APRSC
? 2010 Altera Corporation—Confidential ALTERA, ARRIA, CYCLONE, HARDCOPY, MAX, MEGACORE, NIOS, QUARTUS & STRATIX are Reg. U.S. Pat. & Tm. Off. and Altera marks in and outside the U.S.

Agenda
Signal Bandwidth and Signal Integrity Transmission Line Altera IO Characteristic High Speed Serial Link PCB Layout Guidelines
? 2010 Altera Corporation—Confidential ALTERA, ARRIA, CYCLONE, HARDCOPY, MAX, MEGACORE, NIOS, QUARTUS & STRATIX are Reg. U.S. Pat. & Tm. Off. and Altera marks in and outside the U.S.

Digital Circuit Requirements
Ensures all signals transmitted are received correctly Ensures signals don’t interfere with one another in a way to degrade reception. Ensures signal don’t damage any device Ensures signal don’t pollute the electromagnetic spectrum
? 2010 Altera Corporation—Confidential ALTERA, ARRIA, CYCLONE, HARDCOPY, MAX, MEGACORE, NIOS, QUARTUS & STRATIX are Reg. U.S. Pat. & Tm. Off. and Altera marks in and outside the U.S.

Introduction to Signal Bandwidth
What is a Digital Pulse?
? Ideally it’s a square wave
? Realistically at higher speeds it’s more like a trapezoidal pulse
? And at higher speeds it might even look like a Sin wave
? 2010 Altera Corporation—Confidential ALTERA, ARRIA, CYCLONE, HARDCOPY, MAX, MEGACORE, NIOS, QUARTUS & STRATIX are Reg. U.S. Pat. & Tm. Off. and Altera marks in and outside the U.S. 5

Introduction to Signal Bandwidth
What is the problem with this?
? ? ? ? ?
Increases Data Dependant Jitter Decreases Timing Margins Decreases Voltage Margins Degrades Signal Quality Loss of Bandwidth of the Signal
? 2010 Altera Corporation—Confidential ALTERA, ARRIA, CYCLONE, HARDCOPY, MAX, MEGACORE, NIOS, QUARTUS & STRATIX are Reg. U.S. Pat. & Tm. Off. and Altera marks in and outside the U.S. 6

Introduction to Signal Bandwidth
Bandwidth?
? Scope, Probe, Trace, Connector ? “Not Enough Bandwidth” ? “Bandwidth Limited”
So what is all this fuss about bandwidth?
? Merriam-Webster Definition
1 : A range within a band of wavelengths, frequencies, or energies; 2 : The capacity for data transfer of an electronic communications system
? 2010 Altera Corporation—Confidential ALTERA, ARRIA, CYCLONE, HARDCOPY, MAX, MEGACORE, NIOS, QUARTUS & STRATIX are Reg. U.S. Pat. & Tm. Off. and Altera marks in and outside the U.S. 7

Introduction to Signal Bandwidth
Back to Basics
? Fourier Series
Any periodic waveform can be represented as a combination of simple harmonics
For a Square Wave the Fourier Approximation is
? 2010 Altera Corporation—Confidential ALTERA, ARRIA, CYCLONE, HARDCOPY, MAX, MEGACORE, NIOS, QUARTUS & STRATIX are Reg. U.S. Pat. & Tm. Off. and Altera marks in and outside the U.S. 8

Introduction to Signal Bandwidth
Illustration
27 19 17 15 13 11 9 7 5 3 1 Harmonic 0 Harmonic
? 2010 Altera Corporation—Confidential ALTERA, ARRIA, CYCLONE, HARDCOPY, MAX, MEGACORE, NIOS, QUARTUS & STRATIX are Reg. U.S. Pat. & Tm. Off. and Altera marks in and outside the U.S. 9

Introduction to Signal Bandwidth
Example 1 (Bandwidth of 30ft of CAT5)
2 Gbps 100 Mbps
? 2010 Altera Corporation—Confidential ALTERA, ARRIA, CYCLONE, HARDCOPY, MAX, MEGACORE, NIOS, QUARTUS & STRATIX are Reg. U.S. Pat. & Tm. Off. and Altera marks in and outside the U.S. 10

Introduction to Signal Bandwidth
Example 2 (Tyco XAUI Backplane Simulator)
? 2010 Altera Corporation—Confidential ALTERA, ARRIA, CYCLONE, HARDCOPY, MAX, MEGACORE, NIOS, QUARTUS & STRATIX are Reg. U.S. Pat. & Tm. Off. and Altera marks in and outside the U.S. 11

Introduction to Signal Bandwidth
An ideal world would have infinite bandwidth Proper high speed design considerations must be taken to ensure signal quality
? Bandwidth Limitations ? High Frequency Losses ? Noise Distortions ? $$$
? 2010 Altera Corporation—Confidential ALTERA, ARRIA, CYCLONE, HARDCOPY, MAX, MEGACORE, NIOS, QUARTUS & STRATIX are Reg. U.S. Pat. & Tm. Off. and Altera marks in and outside the U.S. 12

Signal Integrity (SI)
In all broadest sense, refers to all problems that arise in high-speed products due to interconnections The term SI addresses two concerns in the electrical design aspects
? Quality of the signal When it gets there, is it in good condition? ? Timing Does the signal reach its destination when it is supposed to?
? 2010 Altera Corporation—Confidential ALTERA, ARRIA, CYCLONE, HARDCOPY, MAX, MEGACORE, NIOS, QUARTUS & STRATIX are Reg. U.S. Pat. & Tm. Off. and Altera marks in and outside the U.S. 13

Signal Integrity
At the input gate of receiver, signal logic level is ‘1’ or ‘0’ comparing to reference value Vih and Vil
? Above Vih is considered as logic high ? Below Vil is considered as logic low
Max. Overshoot
? 2010 Altera Corporation—Confidential ALTERA, ARRIA, CYCLONE, HARDCOPY, MAX, MEGACORE, NIOS, QUARTUS & STRATIX are Reg. U.S. Pat. & Tm. Off. and Altera marks in and outside the U.S.
Voltage
Voltage
Vih
Vil Time Ideal waveform at the receiver
Ringing
Time Real waveform at the receiver

Signal Integrity
In general the receiver needs to sample the waveform in order to obtain the binary encoded information, usually triggering by the rising edge or the failing edge of a clock
Common Clock Data at driver Data at receiver
? 2010 Altera Corporation—Confidential ALTERA, ARRIA, CYCLONE, HARDCOPY, MAX, MEGACORE, NIOS, QUARTUS & STRATIX are Reg. U.S. Pat. & Tm. Off. and Altera marks in and outside the U.S.

SI Transmission Quality - Eye Diagrams
Reveals combined transmitter characteristics Rise time and Fall time Overshoot, Undershoot and Ringing (Ringback) Duty Cycle Jitter and Noise
Noise
Eye Opening
Jitter
Larger opening indicates a greater tolerance for noise and jitter Larger opening indicates better receiver sensitivity Wide top, base and transition region indicates reduced receiver sensitivity Eye opening can be correlated with Jitter and BER
? 2010 Altera Corporation—Confidential ALTERA, ARRIA, CYCLONE, HARDCOPY, MAX, MEGACORE, NIOS, QUARTUS & STRATIX are Reg. U.S. Pat. & Tm. Off. and Altera marks in and outside the U.S. 16

Typical Signal Integrity Problems
Noise
? Reflection noise Due to impedance mismatch ? Crosstalk noise Due to electromagnetic coupling between signal traces and vias ? Power/Ground noise (SSO) Due to parasitics of the power/ground delivery system during drivers’ simultaneous switching output (SSO), also called Ground bounce, Delta-I noise or SSN
? 2010 Altera Corporation—Confidential ALTERA, ARRIA, CYCLONE, HARDCOPY, MAX, MEGACORE, NIOS, QUARTUS & STRATIX are Reg. U.S. Pat. & Tm. Off. and Altera marks in and outside the U.S. 17

Typical Signal Integrity Problems
Delay
? Path length Due to poor placement and routing ? Propagation speed Dielectric medium (Er) ? Rising time degradation Due to resistive loss and impedance mismatch
? 2010 Altera Corporation—Confidential ALTERA, ARRIA, CYCLONE, HARDCOPY, MAX, MEGACORE, NIOS, QUARTUS & STRATIX are Reg. U.S. Pat. & Tm. Off. and Altera marks in and outside the U.S. 18

Introduction to Transmission Line
What’s the transmission line
? A passive element that connect any two conductors, at
any distance apart
Signal path Return path
? Used to transport a signal from one point to another
point
Cables
Traces on PCB board Bonding wire in IC packages ……
? 2010 Altera Corporation—Confidential ALTERA, ARRIA, CYCLONE, HARDCOPY, MAX, MEGACORE, NIOS, QUARTUS & STRATIX are Reg. U.S. Pat. & Tm. Off. and Altera marks in and outside the U.S. 20