Oscillator Design Guide For ST Microcontrollers Application

• 1 Quartz crystal properties and model
  • Figure 1. Quartz crystal model
  • Figure 2. Impedance representation in the frequency domain
  • Table 1. Example of equivalent circuit parameters
• 2 Oscillator theory
  • Figure 3. Oscillator principle
• 3 Pierce oscillator
  • Figure 4. Pierce oscillator circuitry
• 4 Pierce oscillator design
  • 4.1 Feedback resistor RF
    • Figure 5. Inverter transfer function
    • Table 2. Typical feedback resistor values for given frequencies
  • 4.2 Load capacitor CL
  • 4.3 Gain margin of the oscillator
  • 4.4 Drive level DL and external resistor RExt calculation
    • 4.4.1 Calculating drive level DL
      • Figure 6. Current drive measurement with a current probe
    • 4.4.2 Another drive level measurement method
    • 4.4.3 Calculating external resistor RExt
  • 4.5 Startup time
  • 4.6 Crystal pullability
• 5 Easy guideline for the selection of suitable crystal and external components
• 6 Some recommended crystals for STM32™ microcontrollers
  • 6.1 HSE part
    • 6.1.1 Part numbers of recommended 8 MHz crystals
      • Table 3. EPSON®
      • Table 4. HOSONIC ELECTRONIC
      • Table 5. CTS®
      • Table 6. FOXElectronics®
    • 6.1.2 Part numbers of recommended 8 MHz ceramic resonators
      • Table 7. Recommendable condition (for consumer)
      • Table 8. Recommendable condition (for CAN bus)
    • 6.1.3 Part numbers of recommended 25 MHz crystals (Ethernet applications)
      • Table 9. HOSONIC ELECTRONIC
      • Table 10. FOXElectronics®
      • Table 11. CTS®
    • 6.1.4 Part numbers of recommended 14.7456 MHz crystals (audio applications)
      • Table 12. FOXElectronics®
      • Table 13. ABRACON™
  • 6.2 LSE part
    • Table 14. EPSON TOYOCOM
    • Table 15. JFVNY®
    • Table 16. KDS
• 7 Some recommended crystals for STM8A/S microcontrollers
  • 7.1 Part numbers of recommended crystal oscillators
    • Table 17. KYOCERA
  • 7.2 Part numbers of recommended ceramic resonators
    • Table 18. Recommendable conditions (for consumer)
    • Table 19. Recommendable conditions (for CAN-BUS)
• 8 Some PCB hints
  • Figure 7. Recommended layout for an oscillator circuit
• 9 Conclusion
• 10 Revision history
  • Table 20. Document revision history