Xilinx Virtex-5 RocketIO GTP User Manual page 238

Chapter 13: Design of Transitions
The magnitude of this excess capacitance (C) or inductance (L) can also be extracted from
the TDR waveform by integrating the normalized area of the transition's TDR response.
The respective equations for capacitance and inductance are:
Figure 13-3
238
Td
2Td
Figure 13-1: TDR Signature of Shunt Capacitance
Figure 13-2: TDR Signature of Series Inductance
t2
V
2
∫
tdr
------------------------------------ - d
= – ----- -
Z
0
t1
t2
V
∫
tdr
2Z ------------------------------------ - d
=
0
t1
shows the integration of the normalized TDR area.
t
1
Shaded area goes into the
integral for Equation 13-2
Figure 13-3: Integration of Normalized TDR Area
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C
t ( ) V
–
step
V
step
t ( ) V
–
step
V
step
t
2
UG196_c13_03_051406
Virtex-5 RocketIO GTP Transceiver User Guide
R
50Ω
UG196_c13_01_051406
50Ω
UG196_c13_02_051406
Equation 13-1
Equation 13-2
UG196 (v1.3) May 25, 2007