1.1.1.3 Continuous-Time Linear Equalizers (CTLE)

The CTLEs equalize a lane’s low-pass response to compensate for high-frequency losses in that lane, thereby improving the quality of the received signal. This circuit can be adjusted to compensate for any physical lane mismatches.

There are two transparent stages of CTLE and a separate pair of stages for the decision feedback equalizer (DFE)/eye monitor receive path. The input signal path (Figure   1) is conditioned by tuning the incoming signal allowing the user to observe the effects of the tuning. The DC gain and peak bandwidth of each stage is selected with Libero. CTLE settings can be selected based on DC gain, peaking frequency, and AC gain or with an auto adaptive setting through the Libero transceiver interface configurator. The automatic or adaptive mode uses internally generated settings to the physical channels for lane optimization.