Diode and PCB Termination Techniques
- Diode PCB Parallel Termination
- In certain scenarios, Schottky diodes or fast-switching silicon diodes are viable options for transmission line termination. It is crucial that the diode’s switching speed exceeds four times the signal rise time.
- When determining the impedance of the breadboard and bottom board becomes challenging, employing diode termination can be a practical and time-efficient solution.
- To address ringing issues encountered during system debugging, the addition of diodes can effectively eliminate them.
Key Points on Diode Termination:
- Diode termination, with its low forward voltage drop (typically 0.3 to 0.45V), clamps the input signal, reducing overshoot and undershoot.
- Advantages include replacing Thevenin or RC termination, reducing overshoot/undershoot, and eliminating the need for line impedance matching.
- Disadvantages include limited diode switching speed, making it unsuitable for high-speed systems.
PCB Serial Termination
- PCB serial termination involves inserting a resistor (typically 10Ω to 75Ω) into the transmission line on the PCB near the source to match signal source impedance.
- Benefits of PCB serial termination include requiring only one termination resistor per line, no power supply connection, and low power consumption.
- Drawbacks include the appearance of a half-wave amplitude signal at the source end when signal logic changes due to voltage drop across the serial resistor.
By understanding the nuances of diode and PCB termination techniques, engineers can effectively manage signal integrity and eliminate potential issues in PCB designs.
