SWRA834 May   2025 CC2340R5 , CC2340R5-Q1 , CC2744R7-Q1 , CC2745P10-Q1 , CC2745R10-Q1 , CC2745R7-Q1 , CC2755R10

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1 Introduction
  5. 2 Reference Designs
    1. 2.1 LP-EM-CC2340R53
    2. 2.2 LP-EM-CC2340R5
    3. 2.3 LP-EM-CC2340R5-Q1
    4. 2.4 LP-EM-CC2340R5-RGE-4x4-IS24
    5. 2.5 LP-EM-CC2745R10-Q1
  6. 3 Schematic
    1. 3.1 Schematic Overview
      1. 3.1.1 48MHz Crystal
      2. 3.1.2 32.768kHz Crystal
      3. 3.1.3 Filter
      4. 3.1.4 Decoupling Capacitors
      5. 3.1.5 Antenna Components
      6. 3.1.6 RF Shield
    2. 3.2 I/O Pins Drive Strength
    3. 3.3 Bootloader Pins
    4. 3.4 Serial Wire Debug (SWD) Pins
  7. 4 PCB Layout
    1. 4.1 Board Stack-Up
    2. 4.2 LC Filter
    3. 4.3 Decoupling Capacitors
    4. 4.4 Placement of Crystal Load Capacitors
    5. 4.5 Current Return Path
    6. 4.6 DC/DC Regulator
    7. 4.7 Antenna Matching Components
    8. 4.8 Transmission Lines
    9. 4.9 Electromagnetic Simulation
  8. 5 Antenna
  9. 6 Crystal Tuning
    1. 6.1 CC23xx and CC27xx Crystal Oscillators
    2. 6.2 Crystal Selection
    3. 6.3 Tuning the LF Crystal Oscillator
    4. 6.4 Tuning the HF Crystal Oscillator
  10. 7 Optimum Load Impedance
  11. 8 PA Table
  12. 9 Power Supply Configuration
    1. 9.1 Introduction to Power Supply
    2. 9.2 DC/DC Converter Mode
    3. 9.3 Global LDO Mode
  13. 10Board Bring-Up
    1. 10.1 Power On
    2. 10.2 RF Test: SmartRF Studio
    3. 10.3 RF Test: Conducted Measurements
      1. 10.3.1 Sensitivity
      2. 10.3.2 Output Power
    4. 10.4 Hardware Troubleshooting
      1. 10.4.1 No Link: RF Settings
      2. 10.4.2 No Link: Frequency Offset
      3. 10.4.3 Poor Link: Antenna
      4. 10.4.4 Bluetooth Low Energy: Device Does Advertising But Cannot Connect
      5. 10.4.5 Poor Sensitivity: Background Noise
      6. 10.4.6 High Sleep Power Consumption
  14. 11Summary
  15. 12References

6.1 CC23xx and CC27xx Crystal Oscillators

The CC23xx and CC27xx devices have two crystal oscillators. The high frequency crystal oscillator (HFXT) runs at 48MHz and is mandatory to operate the radio. The low frequency crystal oscillator (LFXT) is used for RTC timing and only required when accurate RTC timing is necessary. For example, synchronous protocols such as Bluetooth Low Energy (see Section 3.1.2).

Both crystal oscillators are pierce type oscillators are shown in Figure 6-1. In this type of oscillator, the crystal and the load capacitors form a pi-filter providing a 180° phase shift to the internal amplifier keeping the oscillator locked at the specified frequency. For this frequency to be correct, the load capacitance must be dimensioned properly based on the capacitive load (CL) parameter of the crystal.

Pierce-Type Oscillator Figure 6-1 Pierce-Type Oscillator

A key difference between the oscillators is that the high frequency oscillator has internal variable load capacitance inside the IC and does not require external load capacitors. The low frequency oscillator needs to have external capacitors to operate properly.