SWRA495L December   2015  – April 2025 CC1310 , CC1350 , CC2620 , CC2630 , CC2640 , CC2640R2F , CC2640R2F-Q1 , CC2642R-Q1 , CC2650 , CC2662R-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1 Oscillator and Crystal Basics
    1. 1.1 Oscillator Operation
    2. 1.2 Quartz Crystal Electrical Model
      1. 1.2.1 Frequency of Oscillation
      2. 1.2.2 Equivalent Series Resistance
      3. 1.2.3 Drive Level
      4. 1.2.4 Crystal Pulling
    3. 1.3 Negative Resistance
    4. 1.4 Time Constant of the Oscillator
  5. 2 Overview of Crystal Oscillators for CC devices
    1. 2.1 24MHz and 48MHz Crystal Oscillator
    2. 2.2 24MHz and 48MHz Crystal Control Loop
    3. 2.3 32.768kHz Crystal Oscillator
  6. 3 Selecting Crystals for the CC devices
    1. 3.1 Mode of Operation
    2. 3.2 Frequency Accuracy
      1. 3.2.1 24MHz and 48MHz Crystal
      2. 3.2.2 32.768kHz Crystal
    3. 3.3 Load Capacitance
    4. 3.4 ESR and Start-Up Time
    5. 3.5 Drive Level and Power Consumption
    6. 3.6 Crystal Package Size
  7. 4 PCB Layout of the Crystal
  8. 5 Measuring the Amplitude of the Oscillations of Your Crystal
    1. 5.1 Measuring Start-Up Time to Determine HPMRAMP1_TH and XOSC_HF_FAST_START
  9. 6 Crystals for CC13xx, CC26xx, CC23xx and CC27xx
  10. 7 High Performance BAW Oscillator
  11. 8 CC23XX and CC27XX Software Amplitude Compensation
  12. 9 Internal Capacitor Array for CC23XX and CC27XX
  13. 10Internal Capacitor Array for CC13xx and CC26xx
  14. 11Summary
  15. 12References
  16. 13Revision History

1.2 Quartz Crystal Electrical Model

A quartz crystal is a piezoelectric device that transforms electric energy to mechanical energy. This transformation occurs at the resonant frequency. Figure 1-2 shows the simplified electric model that describes the quartz crystal, where C0 is the shunt capacitance, LM is motional inductance, CM is motional capacitance, and RM is motional resistance. The model in Figure 1-2 is a simplified model and includes only the fundamental oscillation frequency. In reality, crystals can also oscillate at odd harmonics of the fundamental frequency.

Crystal Symbol and the Electrical Model of a Quartz Crystal Figure 1-2 Crystal Symbol and the Electrical Model of a Quartz Crystal