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					Crystal Oscillator Negative Resistance
        Measurement System

          Cypress-R Team Members
               Tracey Windley
              Adam El-Mansouri

                   Mentor
               Dr. Herb Hess

               Client Contact
               Aaron Brennan
                    Overview
•   Introduction
•   What is the negative resistance of an oscillator?
•   Cypress Crystal Oscillator
•   Oscillator Characterization
•   Measurement System Benefits
•   Current Progress
•   Project Time-Line
•   Summary
                   Introduction
• Goal
  – Design a negative resistance measurement system for crystal
    oscillators.
• Requirements
  – The measurement system must be automated.
  – Less than 10% measurement error.
  – Compatible with multiple oscillator chips.
  – Provide a manual.
  – Compatibility with the Thermonics temperature control chamber
    and I2C programming interface utilized by Cypress
  – Provide correlation between simulation and bench data.
 What is the negative resistance of
           an oscillator?
• The negative resistance of the oscillator is the amount
  of volts per ampere the circuit can deliver to the crystal.
                              I




                                      Oscillator
                  Crystal         V    Circuit




                                 V
• For a given frequency:      R
                                  I
         Negative resistance
• Startup negative resistance determines if
  the oscillator will start oscillation when the
  system is powered up.

• Rule of thumb is that the startup negative
  resistance must be five times the steady
  state negative resistance.
      Cypress Crystal Oscillator
• Block Diagram

                                   Oscillator   Clock Output
                      Crystal
                                    Circuit




                           Freq.                                               Signal Out
 Crystal Pins   ESD                NDA              Amplifier     Buffer
                           Caps



                                                                Chip Package
    Oscillator Characterization
• Performance Parameters
  – Phase noise
  – Jitter
  – Frequency
  – Negative resistance


• Trade-offs exist between these
  parameters.
 Measurement System Benefits
• Benefits
  – Provide Cypress with an accurate, and universal
    negative resistance measurement system that
    correlates with simulation.

  – Provide an industry standard for measuring negative
    resistance.

  – Eliminate old methods of measurement that require
    safety factors to guarantee oscillation.
          Current Progress
• Reviewed previous methods for measuring
  negative resistance of oscillator circuits.

• From first order analysis and simulation,
  we have chosen to target the
  transconductance of the amplifier, and
  from this derive the negative resistance.
                                        Project Time Line

                                                                                                             2006
ID                Task Name                  Start       Finish     Duration
                                                                               Mar   Apr   May   Jun   Jul      Aug   Sep   Oct   Nov   Dec


1    Initial Project Summary                3/1/2006    3/16/2006     2.4w

     Feasibility Study /Theory of
2                                           3/16/2006   5/1/2006      6.6w
     Measurment


3    Initial Test Bench/Order Parts         5/1/2006    6/1/2006      4.8w


4    Build Prototype Setup                  6/1/2006    7/14/2006     6.4w


5    Automate Test Setup                    6/15/2006   7/28/2006     6.4w

     Make Presentations for Senior Design
6                                           7/28/2006   8/28/2006     4.4w
     and Design Expo
                          Summary

• The negative resistance of the oscillator is important for starting
  oscillation.

• It is important to optimize for the negative resistance because of the
  trade-offs between oscillator performance parameters.

• Preliminary studies show that the optimal solution will be to target
  the transconductance of the amplifier. The negative resistance can
  then be mathematically calculated.

• Proposed timeline for completing the project is the end of August
Questions ?

				
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Description: Snapshot PowerPoint Presentation Resistance