SWRA495K December   2015  – April 2024 CC1310 , CC1350 , CC2620 , CC2630 , CC2640 , CC2640R2F , CC2640R2F-Q1 , CC2642R-Q1 , CC2650 , CC2662R-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Oscillator 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. 2Overview of Crystal Oscillators for CC devices
    1. 2.1 24-MHz and 48-MHz Crystal Oscillator
    2. 2.2 24-MHz and 48-MHz Crystal Control Loop
    3. 2.3 32.768-kHz Crystal Oscillator
  6. 3Selecting Crystals for the CC devices
    1. 3.1 Mode of Operation
    2. 3.2 Frequency Accuracy
      1. 3.2.1 24-MHz and 48-MHz Crystal
      2. 3.2.2 32.768-kHz 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. 4PCB Layout of the Crystal
  8. 5Measuring 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. 6Crystals for CC13xx, CC26xx and CC23xx
  10. 7High Performance BAW Oscillator
  11. 8References
  12. 9Revision History

5.1 Measuring Start-Up Time to Determine HPMRAMP1_TH and XOSC_HF_FAST_START

The following code can be used to measure the approximate turn on time of the high frequency crystal for CC26X2 and CC13X2 devices. This function works by counting the number of low frequency clock edges from the enabling of the high frequency clock to the high frequency clock being qualified. For more accurate results, external measurement equipment is required.

uint32_t OSCHF_DebugGetCrystalStartupTime( void )
{
   uint32_t lfEdgesFound = 0 ;
   // Start operation in sync with the LF clock
   HWREG( AON_RTC_BASE + AON_RTC_O_SYNCLF );
   OSCHF_TurnOnXosc();
   while ( ! OSCHF_AttemptToSwitchToXosc() ) {
      HWREG( AON_RTC_BASE + AON_RTC_O_SYNCLF );
      lfEdgesFound ++ ;
   }
   OSCHF_SwitchToRcOscTurnOffXosc();
   return ( lfEdgesFound );
}

For CC26XX and CC13XX, and CC26X2 and CC13X2 devices, the crystal startup time may also be measured using built in driverlib implementation of OSCHF_DebugGetCrystalStartupTime().