1. ISTCMTM
  2. All Volumes and Issues
  3. Volume 84, no.4, 2023
  4. SERIES TERMINATION OF SINGLE-ENDED LVCMOS SIGNALS

SERIES TERMINATION OF SINGLE-ENDED LVCMOS SIGNALS

ISTCMTM.
2023;
Volume 84(4), Number 4
: 5-9
https://doi.org/10.23939/istcmtm2023.04.005
Authors:
  1. Oleh Seheda
  2. Ihor Nazarkevych
1
Lviv Politecnic National University
2
Lviv Polytechnic National University

For synchronous signals with fast edges traces on printed circuit boards are transmission lines, not just conductor connections. If the length of the PCB trace exceeds certain values, it is necessary to match its impedance with the signal source and/or receiver. Impedance mismatches would bring signal reflections from the source to the receiver and back through the trans- mission line. Such reflection or distortion of the signal is called "echo" or "ringing". It is shown in emissions and irregularities of the waveform, especially the rise and fall edge. In this article, practical guidelines for sequential termination of one-way signals are considered that would resolve such effects. The simulations were done for LVCMOS signals [1].

Single-ended signals
synchronous signals
impedance matching
rise/fall time
transmission line
  1. JEDEC STANDARD – JESD8C.01, Minor Revision of JESD8C, June 2006. [Online]. Available: https://www. jedec.org/system/files/docs/JESD8C-01.pdf.
  2. D. Thomas, H. Nasser, M. Hafiz Baharuddin, “Time- domain measurement of near field emissions from complex PCBs”, October 2016. [Online]. Available: https://www. re- searchgate.net/publication/312561763_Time_domain_meas urement_of_near_field_emissions_from_complex_PCBs.
  3. Dr. Johnson, Howard, Dr. Graham, Martin, High-Speed Digital Design, A Handbook of Black Magic, Prentice Hall, 1993. [Online]. Available: https://www.amazon.com/High- Speed-Digital-Design-Handbook/dp/0133957241.
  4. M. Faheemuddin, “What is the signal propagation delay in PCBs”. [Online]. Available: https://www.protoexpress.com/blog/signal-propagation-delay-pcb/.
  5. Lee Ritchey, “Transmission Line Termination Techniques in High-Speed Design”. [Online]. Available: https:// re- sources.altium.com/p/transmission-lines-and-terminations- in-high-speed-design.
  6. B. Olney, “Beyond Design: Transmission Line Termina- tion,” Design007 Magazine, March 2020, p. 36-42. [Online]. Available: https://iconnect007.uberflip.com/i/ 1219242-design007-mar2020/35?.
  7. P. Ghosh, “Techniques to measure and avoid jitter in PCBs”. [Online]. Available: https://www.protoexpress.com/ blog/techniques-to-measure-and-avoid-jitter-in-pcbs/.
  8. O. Bolt, “AC Vs DC Coupled: Battery Storage, Oscillo- scope, and Termination”. [Online]. Available: https://ener- gytheory.com/ac-vs-dc-coupled/.
  9. M. Cox, “Methods to end a 50-ohm transmission line while avoiding the need for DC”. [Online]. Available: https://copyprogramming.com/howto/how-to-terminate-50- ohm-transmission-line-without-drawing-dc.
  10. SiT8008-datasheet.      Datasheet.      [Online].     Available: https://www.sitime.com/support/resource- library/datasheets/sit8008-datasheet.