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Grounding Principles in Mixed-Signal Board Docent Li-Rong Zheng & Prof. Hannu Tenhunen

Grounding Principles in Mixed-Signal Board Docent Li-Rong Zheng & Prof. Hannu Tenhunen Laboratory of Electronics and Computer Systems Royal Institute of Technology (KTH) SE-164 40 Kista, Sweden (lrzheng@imit.kth.se). Outline. Simultaneous switching noise (SSN) Non-ideal return path

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Grounding Principles in Mixed-Signal Board Docent Li-Rong Zheng & Prof. Hannu Tenhunen

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  1. Grounding Principles in Mixed-Signal Board Docent Li-Rong Zheng & Prof. Hannu Tenhunen Laboratory of Electronics and Computer Systems Royal Institute of Technology (KTH) SE-164 40 Kista, Sweden (lrzheng@imit.kth.se)

  2. Outline • Simultaneous switching noise (SSN) • Non-ideal return path • Ground-referenced and power referenced signals • Grounding principles

  3. Simultaneous switching noise (SSN)

  4. Simultaneous switching noise: Component Level

  5. Simultaneous Switching Noise: Component and Board level

  6. Ground noise generation mechanism

  7. CMOS output driver

  8. Power Supply Noise and Signal Delay

  9. Non-Ideal Return Path

  10. Return Path of Signals

  11. Signal Traversing a Ground gap

  12. Modeling a signal traversing a gap (in nH) D: in cm

  13. Non-ideal Return Path

  14. Signal that Change Reference Planes

  15. Ground-Referenced and Power Referenced Signals

  16. Ground Referenceand/or Power reference Dual referenced signal reduces the current through decoupling capacitor

  17. Ground Reference or Power Reference

  18. Ground Reference or Power Reference 6-9

  19. Grounding Principles for Mixed-Signal Systems

  20. Noise coupling through common impedance

  21. Common earth-return current coupling

  22. Single point vs. multipoint ground system

  23. Single point ground systems

  24. Hybrid ground systems

  25. Ground loop

  26. Functional ground layout

  27. AC vs. DC ground loops

  28. Ground return cannot image to signal flow path and will cause an extra inductance. This inductance will cause switching noise voltage on ground (LdI/dt). If other pins share the same ground, crosstalk is also introduced. Common mode ground noise will result to common mode emission in case of drivers for cables/wires are connected to the same ground Resulting current loop can generate differential mode emission Inductance on ground loops (split-plane ground)

  29. Inductance on ground loops (daugther cards)

  30. Ground loop elimination techniques

  31. I/O decoupling and shielding

  32. I/O decoupling and shielding

  33. Component placement on interconnect substrate

  34. Quiet I/O ground

  35. Reduction of loop areas

  36. Use of image planes to reduce radiated emission

  37. Grounding concepts

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