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 ?