SLLA685 July   2026 TCAN4550-Q1 , TCAN4551-Q1

 

  1.   1
  2.   Abstract
  3. 1Basic Introduction to TCAN455x-Q1
    1. 1.1 What is an SBC?
    2. 1.2 What is CAN FD?
    3. 1.3 What are the advantages of the TCAN455x-Q1?
    4. 1.4 Difference between TCAN4550-Q1 and TCAN4551-Q1
  4. 2TCAN455x-Q1 Peripheral Circuit Design
    1. 2.1 Power Supply Pins
    2. 2.2 SPI and IO Pins
    3. 2.3 CAN Pins
    4. 2.4 Clock Pins
    5. 2.5 Other Pins
  5. 3Clock Circuit Design for the TCAN455x-Q1
    1. 3.1 Internal Clock Circuit and Operating Principles
    2. 3.2 Quartz Crystal Clock Mode Principle
    3. 3.3 Quartz Crystal Parameters
    4. 3.4 Quartz Crystal Selection
      1. 3.4.1 Issue of Erroneous Entry into Single-Ended Clock Mode
      2. 3.4.2 Solutions for Erroneous Entry into Single-Ended Clock Mode
  6. 4Conclusion
  7. 5References

3.4 Quartz Crystal Selection

Refer to the application manual. It is recommended that customers select a 40MHz crystal with a maximum ESR of 60Ω and a load capacitance CLoad between 8pF and 24pF.

The equivalent load capacitance is shown in Figure 3-4, and the calculation formula is given in Equation 1.

TCAN455x Crystal Load Capacitance Equivalent CircuitFigure 3-4 TCAN455x Crystal Load Capacitance Equivalent Circuit
Equation 1. C L o a d = ( C i n + C L 2 ) × ( C L 1 + C o u t ) C i n + C L 2 + C L 1 + C o u t + C P C B _ s t r a y

Where:

  • Cout: Equivalent capacitance of the TCAN455x OSC1 output pin, approximately 10pF;
  • Cin: Equivalent capacitance of the TCAN455x OSC2 input pin, approximately 9pF;
  • CL1, CL2: External capacitors from TCAN455x OSC1 and OSC2 to ground, with CL1 = CL2;
  • CPCB_stray: PCB stray capacitance.

After selection, it is recommended that customers measure the waveform at the TCAN455x OSC2 pin under all operating conditions to verify that the voltage is always above 150mV. Otherwise, the device may erroneously switch from quartz crystal clock mode to single-ended clock mode, leading to communication failure (see Section 3.4.1).