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

3.2 Quartz Crystal Clock Mode Principle

The TCAN455x employs a Pierce oscillator architecture. An internal current source drives the external crystal and capacitors to initiate and sustain oscillation, as shown in Figure 3-3 below. Oscillation is generated by the charging and discharging of the load capacitors at each end of the crystal—one side charges while the other discharges. Once the oscillation process begins, it continues unless the system lacks sufficient energy to sustain it.

At start-up, the amplifier output bias current is at its highest level to rapidly charge the discharged OSC1 capacitor. After the OSC1 capacitor is fully charged, it discharges through the crystal, and the OSC2 capacitor begins to charge. When the OSC2 capacitor is fully charged, it discharges back into the OSC1 capacitor, generating oscillation. After start-up, the TCAN455x reduces the bias current, requiring only enough to compensate for energy losses due to parasitic resistance in the circuit.

TCAN455x Pierce Oscillator Simplified SchematicFigure 3-3 TCAN455x Pierce Oscillator Simplified Schematic