Datasheet

SCEA019 - January 2001
7–86 Texas Instruments GTLP Frequently Asked Questions
8 What is distributed capacitance?
Figure 7 is a simplified backplane physical representation, where an equivalent capacitive
load of 12 pF replaces the receivers. The transmitter also has an equivalent capacitive load of
12 pF.
R
TT
R
TT
Tx
1 = 10"
d = 1
A
B
12 pF
12 pF 12 pF 12 pF 12 pF 12 pF 12 pF 12 pF 12 pF 12 pF
Figure 7. Simplified Backplane Physical Representation
The total capacitance (C
t
) of each card is calculated by summing all the capacitive
components associated with the transceiver and the connection to the backplane. Figure 8
shows a typical connection scheme between the backplane stripline and the transceiver
device on the daughter card. Point C is the connection to the backplane stripline, and point D
is the connection to a transceiver integrated circuit. The total capacitance at point C is the sum
of each of the elements in the connection chain.
C
Via
C
pad1
C
pad2
Connector
Device
Stub1
Stub2
D
Figure 8. Typical Backplane Connection Scheme