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

3.5 Drive Level and Power Consumption

The maximum drive level of a crystal is often specified in the data sheet of the crystal in µW. Exceeding this value can damage or reduce the lifetime the crystal. The CC13xx and CC26xx devices drive the crystal with a maximum 1.6 Vpp_differential for the 24/48-MHz crystal and 600 mVpp_differential for the 32.768-kHz crystal. As Section 1.2.3 explains, Equation 5 gives the drive level in W.

A higher total capacitance load and ESR require more power to drive the crystal, increasing the power consumption of the oscillator. Because the 32.768-kHz crystal is on for an extended period of time, this increase is important. Selecting a low ESR and low-CL 32.768-kHz crystal is important to achieve low-power consumption in a low-power mode.

Note: Do not use the internal DC-DC when applying a probe to the probe to the 24 MHz or 48 MHz crystal oscillator pins. Applying the probe can lead to the oscillator stopping and may lead to the internal DC-DC producing a high-output voltage that may damage the device.