Transcript pptx
Reflection suppression methods EECS 713 Liyao Wang Outlines Theory Simulation circuit Termination • • • • • Source termination Load termination Thevenin termination RC termination Diode termination Theory Figure_1 𝑍𝑠 ≠ 𝑍0 ≠ 𝑍𝐿 Reflection 1: Source reflection Reflection coefficient: 𝑍0 − 𝑍𝑠 Γ𝑠 = 𝑍0 + 𝑍𝑠 Reflection 2:Load reflection Reflection coefficient: 𝑍𝐿 − 𝑍0 Γ𝐿 = 𝑍𝐿 + 𝑍0 Theory Set the voltage source as a dc source in which Vdc=100V, 𝑍𝑠 =150Ω, 𝑍0 = 50Ωand 𝑍𝐿 =(10^16) Ω Figure_3[1] Figure_2[1] Simulation circuit Simulation circuit Simulation Result Source termination • Advantage 1) 2) 3) 4) Easy to assemble Reduce ringing Increase signal integrity Reduce EMI • Disadvantage 1) Load reflection still there 2) Increase the rise time of input signal 3) Wasting power Source termination Source termination • Simulation result Load termination • Advantage 1) Easy to assemble 2) Reduce ringing 3) Easy to find the resistor value • Disadvantage 1) Increase power consumption Load termination Load termination Simulation result Thevenin termination Standard: 𝑍0 = 𝑅1 ||𝑅2 𝑅1 22 = 𝑅2 33 𝑅2 𝑉𝑇ℎ𝑒𝑣 = 𝑉𝑐𝑐 𝑅1 + 𝑅2 The standard is not required for all the situation. Thevenin termination • Advantage 1) Good overshoot suppression • Disadvantage 1) Large current drive (increase power consumption) 2) Increase the difficulty of layout 3) Hard to choose the resistor value and Vcc value Thevenin termination Thevenin termination Simulation result RC termination • Advantage 1) Absorbing all the reflection wave 2) Low power consumption • Disadvantage 1) Increase signal delay 2) The time constant of RC circuit may cause reflection 3) In high speed digital design, need to be careful of the capacitor value RC termination RC termination Simulation Result Reference [1] Paul, Clayton R., Introduction to Electromagnetic compatibility, Wiley Series in Microwave and Optical Engineering, 2006. [2]Wakerly, John F., Digita l Design Principles and Practices, Pearson Education, Inc., 2006. [3] R. Jagdale, A. Reddy, and K. Sundeep, “Optimization of reflection issues in high speed printed circuit boards,” in Proceedings of the 12th International Conference on Networking, VLSI and Signal Processing, pp. 108–112, World Scientific and Engineering Academy and Society, 2010