1.2.4.1 CTLE (CDR Mode)

CTLE can be used up to 10.3125 Gbps for short channel, see the Table 1-4. The following example shows the data capture with default Libero SoC settings and optimal CTLE values from IBIS-AMI simulations at 10.3125 Gbps. The system used for the short reach is 5 inch backplane channel along with cables and PolarFire board traces with following transceiver settings:

  • Tx: 400 mV, 0 dB and 100Ω
  • Rx: 100Ω
  • Libero default CTLE: 5 GHz + 7.3 db
  • CTLE from Simulation: 5 GHz + 1.8 db
  • Data Pattern: PRBS31

The following figure shows the eye plot from simulation with Libero SoC default CTLE setting and corresponding eye from the monitor on SmartDebug.

Figure 1-16. Eye Plot and Monitor—Default Setting with Short Reach

The following figure shows the eye plot captured with optimal CTLE setting from simulation and corresponding eye from eye monitor on SmartDebug.

Figure 1-17. Eye Plot and Monitor—Optimal Setting with Short Reach
Important: Eye with simulated CTLE values look better than the Libero SoC default CTLE setting since the Libero SoC default CTLE setting is calibrated to have loss of 6.5 dB which is higher than the loss used in this example.
Default Libero SoC settings work with zero bit error, however, best value is found from the IBIS-AMI simulation. In case of CDR mode with calibration, transceiver tunes the best CTLE setting.

CTLE is used up to 6.8 Gbps for long channel. The following example show the data capture with default Libero SoC settings and optimal CTLE values from IBIS-AMI simulations at 6.25 Gbps. The system used for the long reach is 34 inch backplane channel along with cables and PolarFire board traces:

  • Tx: 1000 mV, -6 dB and 180Ω
  • Rx: 100Ω
  • Libero default CTLE: 3 GHz + 6.8 db
  • CTLE from Simulation: 5 GHz + 7.3 db
  • Data Pattern: PRBS31

The following figure shows the eye from simulation with Libero SoC default CTLE setting and corresponding eye from eye monitor on SmartDebug.

Figure 1-18. Eye Plot and Monitor – Libero Default CTLE Setting with Long Reach

The following figure shows the eye captured with optimal CTLE setting from simulation and corresponding the eye from eye monitor on SmartDebug.

Figure 1-19. Eye Plot and Monitor—Optimal CTLE Setting with long reach

The eye with Libero SoC default CTLE and CTLE from simulation shows similar results.