Signal Integrity Design Using Fast Channel Simulator and Eye Diagram Statistics

Transcription

1 Signal Integrity Design Using Fast Channel Simulator and Eye Diagram Statistics Sanjeev Gupta, Signal Integrity Applications Expert Colin Warwick, Signal Integrity Product Manager Agilent EEsof EDA XTalk1 PRBS TX Channel RX PRBS XTalkN Received Signal PRBS 1

2 Agenda Challenges associated with serial link analysis Introduction to Channel Simulator: Bit-by-bit mode Statistical mode Demo Comparison with measured data and with StatEye Summary and further resources Complete the feedback survey to enter the prize drawing Q&A 2

3 Introduction to Serial Link XTalk1 PRBS TX Channel RX PRBS XTalkN Received Signal PRBS 3

4 Challenges and Solutions with Serial Link Analysis Challenges Low BER performance (10 12 or less) used to imply long simulations Issues with interconnect models Multiple crosstalk channels modeling for transmitter and receiver Solution: ADS Channel Simulator New in ADS 2009: Bit-by-bit mode New in ADS 2009 Update 1: Statistical mode 4

5 Comparison of Techniques in ADS 2009 Update 1 Transient Simulator Channel Simulator: Bit-by-bit mode Channel Simulator: Statistical mode Method Modified nodal analysis of Kirchoff s current laws for every time step Bit-by-bit superposition of step responses Statistical calculations based on step response Applicability Linear and nonlinear circuits LTI, any specific bit pattern, adaptive eq. taps, IBIS AMI LTI, fixed (general) bit pattern, fixed eq. taps BER floor in one minute simulation ~10-3 ~10-6 Arbitrarily low 5

6 Channel Simulator: Bit-by-bit mode 1) SPICE-like transient response of single bit: runs on existing schematic 2) Response of millions of bits per minute using signal processing techniques Superposition ISI 6

7 Channel Simulator: Statistical mode 1) SPICE-like transient response of single bit: runs on existing schematic 2) Statistical calculations including ISI, crosstalk, jitter specification, equalizers, and encoding 7

8 Demo 8

9 ADS Channel Simulator Versus StatEye ADS Statistical Mode ADS Bit-by-bit Mode StatEye Timing Bathtub ADS Channel Simulator (1 M bits) StatEye ADS Statistical Simulator Voltage Bathtub ADS Channel Simulator (1 M bits) ADS Statistical Simulator StatEye TX jitter model Multiple X-talks ADS Accurate treatment of RJ, PJ and DCD Yes StatEye Simplistic: overestimates eye opening No 9

10 Comparison with Measured Data Measurements were performed using Agilent DCA-J 2 10 bit pattern from signal generator ADS Channel Simulator, Bitbit mode (PRBS 2 10 ) Overlaid plot of Measurement and simulated data for ( 2 10 ) bit pattern ADS Channel Simulator, Statistical mode (infinitely long bit sequence) 10

11 Comparison with Measured Data Tyco Backplane Measured eye diagram with four tap FFE equalizer Simulated eye diagram with four tap FFE equalizer using statistical simulator Comparison of measured and simulated data 11

12 Benefits of ADS Channel Simulator One button selection of bit-by-bit or statistical mode Accurate simulation of frequency domain models Enforces passivity and causality on simulated and measured S-parameters Allows arbitrary channel and crosstalk topology: schematic and layout Perform crosstalk analysis for arbitrary number of aggressor channels Requires only short simulation length: pulse response of channels ~10s of bits Produces reliable eye diagram and BER plots within seconds FFE/DFE tap optimization Automatically open a closed eye Accurately model all jitter components (Rj, PJ, DCD) for TX/RX Provide worst case eye diagram performance at a given BER Eye probes are compatible with Agilent s oscilloscope mask file Automatic optimization of eye diagram and BER Batch mode simulation supported for all measurement goals 12

13 Prize Drawing Registrants* who completely fill out the feedback form by October 29, 2009 will be entering into a drawing for: One of two $75 Amazon.com gift certificates One of twenty tickets (each a $648 value) for our new, intensive one-day hands-on class on ADS Channel Simulator Winner choose either face-to-face in Santa Clara, CA or live, interactive, instructor-led, web-based version *Drawing only open to residents of the 50 United States and Canada (except Quebec) 13

14 Summary and Next Steps Summary Explore a large design space quickly using statistical channel simulation and optimization of BER contours versus eye mask goals Next steps Evaluate ADS 2009, shipping now Application page: ADS 2009 Update 1 Product Shipment in 2009H2 14