CLC018AJVJQ National Semiconductor, CLC018AJVJQ Datasheet - Page 14

• Manufacturer Part Number: CLC018AJVJQ
• Manufacturer: National Semiconductor

Specifications of CLC018AJVJQ

• Number Of Arrays: 1
• Differential Data Transmission: Yes
• Mounting: Surface Mount
• Operating Temperature (max): 85C
• Operating Temperature (min): -40C
• Operating Temperature Classification: Industrial
• Cascading Capability: No
• Line Code: NRZ
• On-chip Buffers: No
• On-chip Mux/demux: No
• Lead Free Status / RoHS Status: Not Compliant

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Operation
CALCULATING THE POWER DISSIPATION IN AN
EXPANDED ARRAY
The CLC016 dissipates about 100 mW per active output plus
about 50 mW quiescent power. With all outputs active, this is
about 850 mW. In an expanded array, all devices will dissi-
pate quiescent power, but only those devices with active
outputs will dissipate the 100 mW/output. So, an N-by-M
device array (an 8xN-input-by-8xM-output switch) with all
outputs active will dissipate N x M x 50 mW + 8 x M x 100
mW. A 32-input x 32-output (4 x 4 device) switch array
dissipates 4 x 4 x 50 mW + 8 x 4 x 100 mW = 4W.
CONTROLLED IMPEDANCE TRANSMISSION LINES
AND OTHER LAYOUT TECHNIQUES
All transmission lines whose length is greater than
length of the highest frequencies present in the transmitted
signal require proper attention to impedance control to avoid
distortion of the signal. Digital signals are especially suscep-
tible to distortion due to poorly controlled line characteristics
and reflections. With its 250 ps output transitions, which
imply a bandwidth of 4 GHz or more, transmission lines
driven by the CLC018 must be carefully designed and cor-
rectly terminated. Either microstrip line, which resides on the
outer surfaces of a printed circuit board and paired with an
image ground plane, or stripline, which is sandwiched in an
inner layer between image ground planes, may be used in
CLC018 designs. With either line type, it is important to
maintain a uniform characteristic impedance over the entire
extent of the transmission line system. Likewise, the receiv-
ing end of these lines must be terminated in a resistance
equal to the characteristic impedance to preserve signal
fidelity. Figure 14 shows representative methods of interfac-
ing to and from the CLC018.
Often, when voltage-mode drivers, such as ECL, with low
output impedance (also called equivalent generator resis-
(Continued)
1
⁄
4
wave-
14
tance) are used to drive bus networks, a series resistor
connects the output of the amplifier to the transmission line.
This resistor serves both as a termination for any signals
travelling toward the source- end of the line and as the series
leg of a voltage divider (with the transmission line as the
shunt leg) to reduce the transmitted signal level. This resis-
tor’s correct value is Z
Z
ing end of the line is terminated in a resistance equal to the
value of Z
equal to the line’s Z
where the bus is heavily loaded, the receiving end termina-
tion’s value may need to be reduced to the loaded- Z
line. (Please see the material on distributed loading effects
on line characteristics in the Fairchild F100K ECL 300 Series
Databook and Design Guide).
Current-mode drivers, with their high equivalent generator
resistance, when used as bus drivers require a resistance
equal to Z
as appropriate for the design.
A detailed discussion of digital transmission line design tech-
niques is beyond the scope of this data sheet, but many
good references are available from National Semiconductor
and others. Extensive material is available in the National
Interface Databook, the Fairchild F100K ECL 300 Series
Databook and Design Guide and the Motorola MECL Sys-
tem Design Handbook.
Especially useful is the National Semiconductor Transmis-
sion Line RAPIDESIGNER r Sliderule and user manual AN-
905. The RAPIDESIGNER is available by calling the Na-
tional Semiconductor Customer Response Center in your
area and asking for either Literature Number 633200-001
(ISO Metric units) or 633201-001 (English units). The User
Manual for both versions is Literature Number 100905-002
and is available on our WEB Site at http://www.national.com
as AN-905.
O
may be used successfully in most situations. The receiv-
O
O
at each end of the bus to either power or ground
of the receiving end of the line. A resistance
O
O
works in most situations. In cases
− R
OUT
. However, a value equal to
O
of the