Plane Capacitance, Inductance, Resistanceance
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C = ε0 |
εr |
LW |
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= ε0 εr |
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A |
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εr |
= 225 x10 −15 |
F |
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w |
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h |
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h |
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in |
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L |
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A |
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h |
RDC |
= ρ |
l |
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= ρ |
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l |
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ρ = 0.679 µΩ − inch |
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tw |
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A |
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1 |
0.679 µΩ − in |
= 0 .49 µΩ / Square |
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Resistance /Square |
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= ρ |
= |
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t |
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0.0014 |
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L = µ0 h |
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l |
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µ0 |
= 4πx10 −7 |
H |
= 0.32 |
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nH |
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w |
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inch |
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FR4 Dielectric |
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Thickness |
Inductance |
Capacitance |
(mils) |
(pH/square) |
(pF/inch2) |
8 |
260 |
127 |
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4 |
130 |
253 |
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2 |
65 |
506 |
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Revision 4 |
Copyright Telephonics 2002-2005 |
67 |
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Capacitor Parameters
♦ Physical capacitors have parasitic |
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elements that limit their ability to |
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stabilize supply lines |
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♦ Equivalent series inductance (ESL) |
ESR |
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ESL |
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C |
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♦ Equivalent Series Resistance (ESR) |
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Plots courtesy of Kemet
Revision 4 |
Copyright Telephonics 2002-2005 |
68 |
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Capacitor Parameters
Part |
Package |
Capacitance |
ESL |
ESR |
SRF |
Number |
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(uF) |
(nH) |
(Ω) |
(MHz) |
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C0603C103K5RAC, Kemet |
EIA 0603 |
0.01 |
1.8 |
0.25 |
38 |
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C0805C104K5RAC, Kemet |
EIA 0805 |
0.10 |
1.9 |
0.10 |
12 |
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T491B685K010AS, Kemet |
EIA 3528-21 |
6.8 |
1.9 |
0.3 |
1.4 |
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T494C476K010AS, Kemet |
EIA 6032-28 |
47 |
2.2 |
0.2 |
0.5 |
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f |
SRF |
= |
1 |
Q = |
1 |
= |
XC |
= |
1 |
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2π LC |
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DF |
R |
2π f C R |
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Self Resonant Frequency |
Quality Factor, Dissipation Factor |
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Revision 4 |
Copyright Telephonics 2002-2005 |
69 |
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Capacitor Guidelines
♦Parasitic inductance is predominantly determined by package size
♦Connect capacitor pads as directly as practical
♦Don’t share cap vias
Revision 4 |
Copyright Telephonics 2002-2005 |
70 |
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