CLC018AJVJQ/NOPB National Semiconductor, CLC018AJVJQ/NOPB Datasheet - Page 8

• Manufacturer Part Number: CLC018AJVJQ/NOPB
• Description: IC CROSSPOINT SWITCH 8X8 64PQFP
• Manufacturer: National Semiconductor

Specifications of CLC018AJVJQ/NOPB

• Function: Crosspoint Switch
• Circuit: 1 x 8:8
• Voltage Supply Source: Dual Supply
• Voltage - Supply, Single/dual (±): ±4.5 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 64-QFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: *CLC018AJVJQ; *CLC018AJVJQ/NOPB; CLC018AJVJQ

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Operation
SINGLE ENDED INPUTS
Differential inputs are the preferred method of providing data
to the CLC018, however, there are times when the only
signal available is single ended. To use the CLC018 with a
single ended input, the unused input pin needs to be biased
at a point higher than the low logic level, and lower than the
high logic level. For best noise performance, the middle of
the range is best. For ECL signals this point is about 2 diode
drops below ground. It is possible to bias the unused input
with a low-pass filtered version of the data, as shown in
Figure 5. In some coding schemes there are pathological
patterns that result in long sequences with no data transi-
tions. During these patterns, the bias on the unused input will
drift towards the other input reducing the noise immunity
which makes this scheme undesirable. The most robust
solution for single ended inputs is to place a comparator with
hysteresis in front of the CLC018. Such a part is the
MC10E1652. See Figure 6 for an example of how to hook
this up.
OUTPUT INTERFACING
The outputs of the CLC018 are differential, current source
outputs. They can be converted to ECL compatible levels
with the use of resistive loads as shown in Figure 7. The
output swings will have a similar temperature coefficient to
10KECL if a 1N4148 diode is used to set V
commercial temperature range applications, a 75Ω resistor
can be used as shown in Figure 8. Many circuits with differ-
ential inputs, such as the CLC016 Data Retimer With Auto-
matic Rate Selection, do not require true ECL levels, so the
load resistors can be connected directly to the positive rail as
shown in Figure 9.
FIGURE 5. Single Ended Input to CLC018
FIGURE 6. Single Ended Input to CLC018
(Continued)
OH
. For most
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OUTPUT SIGNAL QUALITY
The output signal eye pattern shown in Figure 10 was ac-
quired using an Agilent 86100A scope and 86112A plug in
along with a TEK P6330 3GHz differential probe. The differ-
ential signal was probed across the output pins of the
CLC018. 75 Ohm pull up resistor were used as shown in
Figure 9. A PRBS23 pattern was driven through the part, and
the resulting eye pattern is shown in Figure 10. The eye
pattern is affected by the HF roll-off of the probe which
degrades the output transition time and affects jitter. Even
with this loading the CLC018 provides excellent signal qual-
ity and low jitter at 1.485 Gbps. Note 150 ps/div and 250
mV/div
FIGURE 9. Connecting the CLC018 to the CLC016
FIGURE 7. Generating 10k ECL Outputs
FIGURE 8. Generating ECL Outputs
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