Electrical Package Design TKK 2009 Lecture 2

Transcription

1 Electrical Package Design TKK 2009 Lecture 2 James E. Morris Dept of Electrical & Computer Engineering Portland State University i Electrical Package Design Lecture topics A: Introduction CMOS; R, L, & C Lecture topics B: Transmission lines Z 0, velocity, lossless lines, lossy lines Lecture topics C: Transmission lines Transmission line reflections Lecture topics D: Transmission lines Crosstalk Lecture topics E: Electromagnetism & Modeling Lecture topics F: Electromagnetic Compatibility 2 1

2 Lecture topics A: Introduction CMOS; R, L, & C 1. Interconnect modeling 2. Resistance, inductance, & capacitance R, L, & C 3. Skin effect 4. Ground planes 5. MOS devices and CMOS 6. Delta-I (ΔI) switching noise 3 1. Interconnect modeling 4 2

3 Three modeling approaches: Circuit element models Transmission line modeling Electromagnetic wave modeling 5 (a) ωl >> R, (b) R >> ωl, (c) R 0 6 3

4 2. R, G, L, and C Conductor: R = ρl/a = ρl/wt R/L = ρ/wt Dielectric: G = σa/d = σlw/d G/L = σw/d C = εa/d = εlw/d C/L = εw/d Note: L=length in this slide; used for inductance later 7 Capacitance/unit length: Generalized geometries (a) Visual approximations (b) (c) (d) (e) (f) 8 Method of images Graphical approximations Experimental field plotting Numerical techniques (mesh/iteration) Analytical: V=ΣV i for charges Q i 4

5 (g) Method of Moments: Example For point 2 9 Method of Moments Example 10 5

6 11 Inductance of a Straight Wire Magnetic Field Internal/External Inductances 12 6

7 Internal Inductance 13 External Inductance: Basic formula 14 7

8 Compare:- 15 External Inductance: 2-wire line 16 8

9 Straight Wire: Radial Electric Field 17 Magnetic and Electric Fields: (2π) -1 ln(r 2 /R 1 ) = εv/q (electric) = ψ e /Iμ 0 18 i.e. L e.c = constant = μ 0 ε 9

10 Lead inductances Skin Effect 20 10

11 21 R=ρl/πr 2 R skin =ρl/2πrδ as f, and ωlint= ω(μ0/8π) l R skin as f 22 11

12 23 4. Ground planes 24 12

13 Loss of coupled return inductance, EMI MOS devices and CMOS 26 13

14 Derivation of MOSFET characteristic equations Now set (μw/2l)c ox = k 27 CMOS dynamic characteristics (part 1) 28 14

15 CMOS dynamic characteristics (part 2) 29 Switching current (1) 30 15

16 Switching current (2) Delta-I (ΔI) switching noise ΔV = L di/dt 32 16

17 33 Example to show typical values 34 17

18 B/C/D. Transmission line effects 35 Lecture topics B: Transmission lines (Z 0, velocity, lossless, lossy) 1. Transmission line theory Characteristic impedance Z 0 Attennuation, dispersion, velocity 2. Z 0 calculations 3. Lossless line Distortionless transmission Shape factor 4. Z 0 for practical geometries 5. Effects of loss Distortion 36 18

19 1. Transmission line theory 37 Summary 38 19

20 2. Z 0 calculations Need L, C Also gives β, v Easiest geometry is coaxial line (radial symmetry) (a) Dielectric: C/unit length (b) Leakage conductance: G/unit length (c) Inductance: L/unit length Lossless lines 40 20

21 41 4. Practical Z

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23 5. Lossy lines 45 Lecture topics C: Transmission lines Transmission line reflections 1. Reflection coefficients 2. Basic cases: Matched and open circuit 3. Generalized mismatches Source and load 4. Bounce chart/lattice diagram 5. Rfl Reflections from discontinuitiesi ii 46 23

24 1. Reflection Coefficient significant cases: Γ VL = (R L -Z 0 )/ (R L +Z 0 ) Load R L = Z 0 (above) Γ VL = 0 Open circuit load: R S = Z 0 (Γ VL = 1) R S = 0 (Γ VS = -1) Short circuit load R L = 0, Γ VL =

25 49 3. Mismatched load &/or source 1 volt pulse, Z 0 = 78Ω Consider R L = 78Ω cases first, then vary R L for (a) R S =Z 0 (b) R S << Z 0 (c) R S >> Z

26 4. Bounce chart (lattice diagram) Calculate reflection coefficients Distance / time diagram Transfer data to waveform plots Example: Open circuit line Discontinuities 52 26

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28 Summary 55 Lecture topics D: Transmission lines Crosstalk 1. Inductive and capacitive coupling 2. Forward and backward noise 3. Far end and near end noise 4. Incremental model and formulae 5. Crosstalk examples 6. Capacitive crosstalk systems 7. No ground plane 56 28

29 1. Inductive and capacitive coupling Incremental line model Crosstalk polarities Forward & backward noise 3. Near end & far end 58 29

30 4. Theory: line segment 59 Far end overview 60 30

31 Backward wave model 61 Near end pulse shape 62 31

32 Near End Saturation Pulse crosstalk noise examples Drive pulse: 0.5 volt, t width =20ns, t rise =t fall =1ns Forward noise: matched Backward: matched 32

33 Not matched Forward( Far end) Backward (Near end) Ground coupled crosstalk 66 33

34 7. Mutual capacitances Even/odd modes 67 Microstrip Lecture topics E: Electromagnetic Modeling Transmission line 68 34

35 3. Electromagnetic Modeling (Fang) Finite element mesh 69 a. Current pulse excitation of line 70 Electric field distribution on line 35

36 b. Chamfered right angle bend Pulse after reflection from corner 71 c. Orthogonal line crosstalk 72 36

37 Lecture topics F: Electromagnetic Compatibility 1. Antennas 2. Emissions 3. Susceptibility EMI/EMC Models: Loop/Dipole Antennas 74 37

38 L I 1 d I 2 L R s d H n E t R L 75 Electromagnetic compatibility/interference m 2. EMI/EMC Models: Emissions At far field distance r ( λ=c/f) from the line of length L and area A = L.d, the radiated electric field strength is E = E D + E CM where E D due to the differential current I D is E D = x f 2 A I D /r V/m and E CM due to the common mode current I CM is (for L λ) E CM = 4π x 10-7 f 2 L I CM /r V/m where I D = (I 1 + I 2 )/2 and I CM = (I 1 -I 2 )/2. Common mode currents are ideally zero, but small values can lead to CM dominance over differential. For the differential current, the maximum value can be taken to be the supply current, but the user must specify a non-ideal common mode estimate. For digital systems, use f = 2π/t r. For other geometries, other expressions for A are valid. There are many different standards for EM radiation limits, but for guidance the EU limit is E 100μV/m at r = 10m (class A) or 3m (class B)

39 EMI/EMC Models: Susceptibility jwμ o L d H n + V s - R L R s -jwcld E t V L + - odels Susceptibility For the line shown, with capacitance C per unit length, e.g. C = π ε r ε 0 /ln(d/r w ) for parallel wires, the induced voltages are V S = -jω [R L R S / (R L + R S )] [Ld] [C - (μ 0 /η 0 )/R L ] V L = -jω [R L R S / (R L + R S )] [Ld] [C + (μ 0 /η 0 )/R S ] where E = E t = η 0 H n, and η 0 = 120π = 377Ω. As an example of an EU standard, d the device must function in a field of E = 3V/m