Channel Insertion Loss - Channel Insertion Loss - XAPP1392

One ultimate challenge for 112 Gbps electrical interfaces is achieving the desired physical reach while still meeting the constraints of power consumption and bandwidth-limited channels. High-speed data rate transmissions suffer from the frequency-dependent attenuation and dispersion induced by PCB-based or electrical cable-based interconnects.

As illustrated in the following figure, frequency-dependent attenuation and dispersion arise from frequency-dependent conductor loss and dielectric loss, where conductor loss can be subdivided into smooth copper loss due to skin effects and additional loss due to a rough conductor surface. While the die bump-to-die bump channel insertion loss budget is around 35 dB for long reach applications in each generation from 25 Gbps to 100 Gbps, low-loss PCB material, smoother copper with advanced surface treatments, and/or wider traces are required to fulfill the IL budget in the 100 Gbps era.

Figure 1. PCB Material Loss Decomposition

The designed channel must meet the recommended maximum and minimum channel insertion loss stipulated in corresponding electrical standards. When paired with a long reach-capable transceiver, the Versal device GTM transceiver can support up to 30 dB ball-to-ball loss (refer to the corresponding standards for the maximum channel IL budgets) at Nyquist (14 GHz for 56 Gbps PAM4 or 28 GHz for 112 Gbps PAM4) with Reed-Solomon (544, 514) Forward Error Correction (RS (544, 514) FEC).

The maximum IL a Versal device GTM transceiver can support also depends on the channel characteristics like discontinues and crosstalk. The designed channel should be evaluated with the channel compliance methods stipulated in the corresponding standard to verify the conformance.