Digital Signal Processing Reference
In-Depth Information
Problems
Answers to these problems are available on the Artech House Web site at http://
www.artechhouse.com/static/reslib/thierauf/thierauf1.html.
12.1 A parallel termination uses 120
5% resistors for
R
1 and
R
2 (shown in
Figure 12.3). What is the likely impedance of the trace that this terminates?
Ω
,
±
12.2
5% tolerance
resistors are adequate or if resistors with tighter tolerance are necessary.
12.3 Compare the performance of a 60
Using the same setup described in Problem 12.1, determine if
±
Ω
Thevenin termination shown in Figure
5% resistor with the parallel termination illustrated in
the previous problem.
12.4 Find the proper values for
R
1 and
R
2 (shown in Figure 12.3) to terminate
a 75
12.3 that uses a
±
coax cable to 1V when
V
dd
is 5V.
12.5 A system uses logic devices that have an input threshold of 2.4V. To guar-
antee that this exceeds the receiver threshold, the value of
V
term
in Figure
12.3 is set to be 3V.
R
term
must be no less than 130
Ω
to avoid exceeding the
current handling ability of the driver. Find the value of
R
1 and
R
2 when
V
dd
is 5V.
Ω
12.6
Determine the difference in power dissipation in Figure 12.3 when the bus is
held low if
R
1 and
R
2 are both 100
Ω
. Assume that
V
dd
is 3.3V and
R
ds_on
.
12.7 What is the minimum value capacitor that should be used to AC terminate
a 65
is 12
Ω
trace that is carrying a 33-MHz clock?
12.8 An integrated RC network used for AC termination has a resistance
R
term
of 50
Ω
and a capacitance
C
term
of 470 pF. What is the lowest frequency that
this network can reasonably be expected to terminate?
12.9 What is the proper value for
R
S
1
,
R
S
2
, and
R
S
3
in Figure 12.9 when
T
1 has
an impedance of 50
Ω
? Assume
that the signal rise time is 50 pS, the load capacitors are all 2.5 pF, and the
transmission lines all have a delay of 2 ns.
12.10 Using the same information as in the previous problem, what should be the
values of
V
term
and
R
term
1
through
R
term
3
when
V
dd
Ω
and the impedance of
T
2 and
T
3 is 65
Ω
=
3.3V and the receivers
V
represented by
C
L
1
through
C
L
3
switch at
?
dd
2
12.11 Find the loaded impedance of the transmission line shown in Figure 12.13
when
Z
o
is lowered to 40
Ω
. How does this change compare to the 65
Ω
example given in Section 12.7.2?
12.12 What values should be chosen for transmission line
T
1 and resistor
R
S
and
R
term
1
through
R
term
3
in Figure 12.16 when
T
2,
T
3, and
T
5 are 50
Ω
and
?
12.13 Three state drivers are used to drive data between nodes with the topology
shown in Figure 12.16. Assume that reducing power is important in this ap-
plication, and to facilitate this, the bus will be made inactive (set to the high-
impedance state) at frequent intervals. If the transmission lines are 50
T
4 is 65
Ω
and
V
dd
is 3.3V, what form of parallel termination (shown in Figure 12.3) is the
best choice to reduce power?
Ω
