LVDSEVAL-001 National Semiconductor, LVDSEVAL-001 Datasheet - Page 7

• Manufacturer Part Number: LVDSEVAL-001
• Description: EVALUATION BOARD FOR DS90LV031A
• Manufacturer: National Semiconductor

Specifications of LVDSEVAL-001

• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: *LVDSEVAL-001

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The PCB interconnect signal (LVDS Channel #4) can be measured at the receiver inputs (test points A4
and B4). Due to the short interconnect path via the PCB little distortion to the waveform is caused by the
interconnect. See figure 4. Note that the data rate is 50 Mbps and the differential waveform (V
shows fast transition times with little distortion.
The cable interconnect signal is also measured at the receiver inputs (test points A1 & B1 and A2 & B2).
Due to the characteristics of the cable some waveform distortion has occurred. Depending upon the cable
length and quality, the transition time of the signal at the end of the cable will be slower than the signal at
the driver’s outputs. This effect can be measured by taking rise and fall measurements and increasing the
cable length. A ratio of transition time to unit interval (minimum bit width) is a common gauge of signal
quality. Depending upon the application ratios of 30% to 50% are common. These measurements tend to
be more conservative than jitter measurements. The waveforms acquired with a SCSI-2 cable of 1 meter
and also 2 meters in length are shown in figure 5 and 6. Note the additional transition time slowing due to
the cable’s filter effects on the 2 meter test case.
Figure 5: LVDS Channel #1 Waveforms - 1m Cable Interconnect
Figure 4: LVDS Channel #4 Waveforms — PCB Interconnect
A4
B4
A4-B4
04
A1
B1
A1-B1
01
DIFF
)