SNLA421 December   2022 DS320PR810 , SN75LVPE5412 , SN75LVPE5421

 

  1.   Abstract
  2.   Trademarks
  3. 1Introduction
    1. 1.1 Add-in-Card (AIC) Form Factor
  4. 2Compliance Tests
    1. 2.1 Workshop Test Results
    2. 2.2 Electrical Testing Results
  5. 3Electrical Performance
    1. 3.1 Effects of EQ Index on Time Domain Signal
    2. 3.2 Effects of EQ Index on the Eye Diagram
    3. 3.3 Effects of DC Gain on Time Domain Signal
    4. 3.4 Effects of DC Gain on the Eye Diagram
  6. 4Compliance Setting Fine Tuning
  7. 5Summary
  8. 6References

2.2 Electrical Testing Results

Some of the most relevant testing is done with compliance software to measure at-speed electrical and eye performance. Table 2-2 and Table 2-3 shows system eye opening measurements after passing through the linear redriver.

Table 2-2 Eye Width Measurements at BER Gen5
Equalization Measured Value (ps) Test Result Margin (ps) Low Limit (ps)
P0 Gen5 15.350 Pass 4.725 10.625
P01 Gen5 15.831 Pass 5.206 10.625
P02 Gen5 14.521 Pass 3.896 10.625
P03 Gen5 14.770 Pass 4.145 10.625
P04 Gen5 12.306 Pass 1.681 10.625
P05 Gen5 17.315 Pass 6.690 10.625
P06 Gen5 17.509 Pass 6.884 10.625
P07 Gen5 17.655 Pass 7.030 10.625
P08 Gen5 18.012 Pass 7.387 10.625
P09 Gen5 18.311 Pass 7.686 10.625
Table 2-3 Eye Height Measurements at BER Gen5
Equalization Measured Value (mV) Test Result Margin (mV) Low Limit (mV)
P0 Gen5 32.167 Pass 10.167 22
P01 Gen5 30.724 Pass 8.724 22
P02 Gen5 31.913 Pass 9.913 22
P03 Gen5 33.157 Pass 11.157 22
P04 Gen5 34.383 Pass 12.383 22
P05 Gen5 41.763 Pass 19.763 22
P06 Gen5 41.198 Pass 19.198 22
P07 Gen5 32.055 Pass 10.055 22
P08 Gen5 35.180 Pass 13.180 22
P09 Gen5 41.540 Pass 19.540 22

Another test which highlights linear redriver performance is the Tx Preset testing. This test uses the redriver test partner to generate each of the PCIe Tx presets P0 – P10. The ideal and measured values with the redriver are shown in Table 2-4. The performance of the redriver is based on its own linearity and the Tx performance of the test partner. Ideally the redriver will exactly emulate the test partner performance.

Table 2-4 Tx Preset Summary
Preset Ideal Preshoot (dB) Ideal De-Emphasis (dB) Redriver Preshoot (dB) Redriver De-Emphasis (dB)
P0 0 -6 0.00 -6.85
P1 0 -3.5 0.00 -4.15
P2 0 -4.4 0.00 -4.64
P3 0 -2.5 0.00 -2.83
P4 0 0 0.00 0.00
P5 1.9 0 1.81 0.00
P6 2.5 0 2.25 0.00
P7 3.5 -6 3.23 -6.46
P8 3.5 -3.5 3.28 -4.45
P9 3.5 0 3.04 0.00
P10 0 -10 0.00 -10.51

The Preset test is performed on a very low frequency portion of the compliance waveform. The test is run at such a low frequency to minimize PCB and cabling losses in the system. The lines use data from Presets P7 – P10 which form the perimeter of the Tx equalization space, other Presets use lower values of Preshoot and De-emphasis.


GUID-20221109-SS0I-K9MR-G8NZ-SWMXCRBHHNRM-low.png

Figure 2-1 Graphical Representation of Tx Equalization