1. Penn ESE370 Fall2013 -- DeHon 1 ESE370: Circuit-Level Modeling, Design, and Optimization for Digital Systems Day 35: November 25, 2013 Inductive Noise

2. Today Inductive Responses Calculating L Where do inductances show up Impact of inductance on digital circuits How address Penn ESE370 Fall2013 -- DeHon 2

3. Response What happens here? Penn ESE370 Fall2013 -- DeHon 3

4. LC Response Penn ESE370 Fall2013 -- DeHon 4 V2V2

5. LC Response Penn ESE370 Fall2013 -- DeHon 5

6. LC Response Penn ESE370 Fall2013 -- DeHon 6

7. LC Response Penn ESE370 Fall2013 -- DeHon 7

8. LC Response Penn ESE370 Fall2013 -- DeHon 8

9. LC Response Penn ESE370 Fall2013 -- DeHon 9

10. LC Response Penn ESE370 Fall2013 -- DeHon 10

11. LC Response Penn ESE370 Fall2013 -- DeHon 11

12. Response? Penn ESE370 Fall2013 -- DeHon 12

13. RLC Response Penn ESE370 Fall2013 -- DeHon 13 V2V2

14. RLC Response Penn ESE370 Fall2013 -- DeHon 14

15. RLC Response Penn ESE370 Fall2013 -- DeHon 15

16. Solving for w Penn ESE370 Fall2013 -- DeHon 16

17. RLC Penn ESE370 Fall2013 -- DeHon 17

18. RLC Penn ESE370 Fall2013 -- DeHon 18

19. RLC For What happens? –Oscillation What else happens? –Decay Penn ESE370 Fall2013 -- DeHon 19

20. DecayOscillation RLC For Penn ESE370 Fall2013 -- DeHon 20

21. RLC Response (R=100) Penn ESE370 Fall2013 -- DeHon 21

22. When Oscillate For what R does this particular circuit oscillate? Penn ESE370 Fall2013 -- DeHon 22

23. RLC Response Penn ESE370 Fall2013 -- DeHon 23

24. Inductance of Wire Penn ESE370 Fall2013 -- DeHon 24

25. Inductance: Wire over Ground Plane Inductance per cm with h=3mil, w=5mil? Penn ESE370 Fall2013 -- DeHon 25

26. Lwire Penn ESE370 Fall2013 -- DeHon 26 C and L per unit length

27. Chip Inductance C wire = 0.16 pF  for the 1mm) C wire = 0.16nF/m Permeability  0 ≈  Si02 =12.6×10 -7 H/m Permitivity  ox =3.5×10 -11 F/m Penn ESE370 Fall2013 -- DeHon 27

28. On Chip C wire = 0.16 pF  for the 1mm) C wire = 0.16nF/m Permeability  0 ≈  Si02 =12.6×10 -7 H/m Permitivity  ox =3.5×10 -11 F/m  pH (for 1 mm) Penn ESE370 Fall2013 -- DeHon 28

29. Comparisons 5mil trace on PCB (preclass 2) Protoboard wires (0.6mm diameter) –About 7nH/cm –http://www.consultrsr.com/resources/eis/induct5.htm On chip wire –0.28nH/mm = 2.8nH/cm Penn ESE370 Fall2013 -- DeHon 29

30. Inductors Bond pads Chip leads Long wire runs Cables Penn ESE370 Fall2013 -- DeHon 30 Src: http://en.wikipedia.org/wiki/File:Wirebonding2.svg

31. Where Arise Penn ESE370 Fall2013 -- DeHon 31

32. Signal Path Penn ESE370 Fall2013 -- DeHon 32

33. Power Ground Penn ESE370 Fall2013 -- DeHon 33

34. Shared Power/Ground Example: 74x04 Penn ESE370 Fall2013 -- DeHon 34

35. Estimate R eq, C eq for gates in parallel –R 0 = 25K  –C 0 = 0.01 fF say 10C 0 =0.1fF for typical load 250 gates switching at clock R eq = 100  C eq =25fF Assume L=1nH How long to settle? Oscillate? Penn ESE370 Fall2013 -- DeHon 35

36. Power Ground Penn ESE370 Fall2013 -- DeHon 36

37. RLC Response Penn ESE370 Fall2013 -- DeHon 37

38. Today’s Chips How many gates? Penn ESE370 Fall2013 -- DeHon 38

39. Multiple Power/Ground Pins Use many power/ground pins How many pins on a package? Divide switching gates by pins –To get effective load on each pin Penn ESE370 Fall2013 -- DeHon 39

40. How Improve Penn ESE370 Fall2013 -- DeHon 40

41. How Improve? Collect thoughts Penn ESE370 Fall2013 -- DeHon 41

42. Minimize the L Make wires short Use power and ground planes –Think of power plane as a very wide wire Impact on C and L? Penn ESE370 Fall2013 -- DeHon 42

43. Add Good C’s Bypass Capacitors – inside the inductances –On board –On package –On chip Penn ESE370 Fall2013 -- DeHon 43

44. Bypass Capacitor Example Penn ESE370 Fall2013 -- DeHon 44

45. Bypassed Supplies (@ transistor) Penn ESE370 Fall2013 -- DeHon 45

46. Bypassed Output Penn ESE370 Fall2013 -- DeHon 46

47. Minimize Current Draw More Power/Ground Pins Slower rise/fall times Spread out switching Penn ESE370 Fall2013 -- DeHon 47

48. Idea Long wires are inductive –Avoid them –Especially on power supplies Bypass capacitors help Penn ESE370 Fall2013 -- DeHon 48 DecayOscillation

49. Admin Tuesday: Project 2 due Wednesday Lecture Penn ESE370 Fall2013 -- DeHon 49