1. Crystal Oscillator Negative Resistance Measurement System
Cypress-R Team Members
Tracey Windley
Adam El-Mansouri
Mentor
Dr. Herb Hess
Client Contact
Aaron Brennan

2. Overview Introduction
What is the negative resistance of an oscillator?
Cypress Crystal Oscillator
Oscillator Characterization
Measurement System Benefits
Current Progress
Project Time-Line
Summary

3. Introduction Goal Requirements
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.

4. 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.
For a given frequency:

5. 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.

6. Cypress Crystal Oscillator
Block Diagram

7. Oscillator Characterization
Performance Parameters
Phase noise
Jitter
Frequency
Negative resistance
Trade-offs exist between these parameters.

8. Measurement System 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.

9. 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.

10. Project Time Line

11. 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

12. Questions ?