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

3.2.1 24MHz and 48MHz Crystal

Because the 24MHz and 48MHz crystal oscillators are used as a reference to generate the RF signal, any crystal frequency deviation is directly transferred to deviation of the RF signal. For example, 10ppm frequency deviation leads a deviation in RF carrier frequency of 10ppm. Select a crystal with performance within the limits of the RF specifications.

  • For 802.15.4 (Thread/ ZigBee®), the maximum deviation in carrier frequency is limited to ±40 ppm (see [1]).
  • For Bluetooth® low energy, the limit is ±40 ppm (see [2]).
  • Customers of CC13X2 who require frequency accuracy tighter than the crystal can provide can also use a TCXO.