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Cubic Function Generator Design

CSE598A/EE597G Spring 2006. Cubic Function Generator Design. Boram Lee, Jaehyun Lim Department of Computer Science and Engineering The Pennsylvania State University. Crystal Oscillator – f vs. T characteristic. Z. AT-cut. 25. . 35¼ o. 20. 8 ’. Y. -1’. 15. 7 ’. 0 ’. 6 ’. Z.

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Cubic Function Generator Design

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  1. CSE598A/EE597G Spring 2006 Cubic Function Generator Design Boram Lee, Jaehyun Lim Department of Computer Science and Engineering The Pennsylvania State University

  2. Crystal Oscillator – f vs. T characteristic Z AT-cut 25  35¼o 20 8’ Y -1’ 15 7’ 0’ 6’ Z 10 Y-bar quartz 1’ 5’ 5 (ppm) 4’ 2’ 0 3’ f f 3’ -5 2’ 4’ 1’ -10 Inflection Point 5’ 0’ -15 6’ -1’ -20 7’ 8’ -25 -45 -40 -35 -30 -25 -20 -15 -10 -5 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90

  3. Crystal Oscillator – f vs. T characteristic • XO (crystal oscillator) • does not contain means for reducing the crystal’s f vs. T characteristic • OCXO (oven controlled crystal oscillator) • crystal and other temperature sensitive components are in a stable oven • oven temperature adjusted to the temperature where the crystal’s f vs. T has zero slope • over 1000X improvement over the crystal’s f vs. T variation • Large package, high power consumption – not suitable for mobile/battery powered devices • TCXO (temperature compensated crystal oscillator) • temperature sensor generates a correction voltage • the correction voltage applied to a variable reactance in the crystal network (ex. varactor) • the reactance variations compensate for the crystal’s f vs. T characteristic • about 20X improvement over the crystal’s f vs. T variation

  4. Uncompensated crystal frequency Frequency / Voltage T Compensated frequency of TCXO Compensating voltage Cubic Function Generator • Application • frequency compensation in TCXO

  5. TCXO – Temperature Compensation : linear coefficient of temperature depend on cut-angle : cubic coefficient of temperature : inflection point temperature (≈ 25 °C) : actual temperature

  6. Cubic Function Generator • Design I Cubic Functional Voltage Generator cubic term voltage conversion circuit (Low Temperature) cubic term voltage conversion circuit (High Temperature) Cubic Wave Temperature sensor ∑ linear term voltage conversion circuit

  7. Cubic Function Generator • Design I out out Vg T T

  8. Cubic Function Generator • Design I Vg out T out T

  9. Cubic Function Generator • Design I out out out T T T <low temperature> <high temperature> <linear term> out <pseudo cubic wave> T

  10. Cubic Function Generator • Design II linear linear input square cubic wave cube

  11. Cubic Function Generator • Design II • analog voltage multiplier • analog voltage adder • op-amp • bias circuits

  12. Cubic Function Generator • Specification • power consumption : 50 mW • size : 0.3 mm x 0.3 mm • supply : 5 volt single supply • input range : 1.5 V ~ 3.5 V • TSMC 0.35 / AMIS 0.5

  13. Cubic Function Generator • Schedule • week 1 : op-amp design, test Design I • week 2, 3 : multiplier design • week 4, 5 : bias circuits, project progress presentation • week 6 : make improvements of basic blocks • week 7 : finalize of cubic function generator • week 8 ~ : final revision of cubic function generator, layout, project final presentation

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