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

2.1 24MHz and 48MHz Crystal Oscillator

Figure 2-1 shows a simplified block diagram of the XOSC-HF. The oscillator circuit consists of an inverting amplifier, a feedback net, capacitors, and a crystal. The CC devices have an internal capacitor array that can be adjusted and eliminates the requirement for external loading capacitors. The cap-array can be adjusted by the Customer Configuration Flash (CCFG) within a range of 3.5pF to 10pF. For reliable operation, TI requires operating the crystal with CL from 5 to 9pF. The CC13xx/CC26xx Hardware Configuration and PCB Design Considerations application note shows how to set this value. If no external capacitors are used, then the value of CL is determined by the internal loading capacitors plus board parasitic capacitance CP.

Simplified Block Diagram of the CC Devices High-Frequency Oscillator With Quartz CrystalFigure 2-1 Simplified Block Diagram of the CC Devices High-Frequency Oscillator With Quartz Crystal

The 24MHz or 48MHz crystal is controlled with a control loop described in Section 2.2 and Section 2.3.