2 Transmitter Pre-Emphasis and Receiver Equalizer

ISOUSB211 transmitter consists of nine programmable pre-emphasis settings, and the receiver consists of nine programmable equalizer settings implemented with continuous-time linear equalizer (CTLE) architecture. We can estimate these nine pre-emphasis/equalizer characteristics using a 1-zero and 2-pole system that peaks at 240 MHz from 0.25 dB to 4 dB to the first-order approximation. The CTLE amplifies the high-frequency signal around 240 MHz while keeping the low-frequency signal unchanged. The pre-emphasis/equalizer boosts the high-frequency signal, and this has the effect of reducing the rise and fall times and thus allows the signal to get closer to the power rail and complete a transition within a symbol interval as shown in Figure 2-1 and Figure 2-2.

Figure 2-3 shows the time-domain waveforms of the nine ISOUSB211 transmitter pre-emphasis with a data pattern of long run-length of ones and zeros. The emphasized signal has a fixed width of a single bit (1/480 Mbps), and its strength is scaled proportionally from 00 to 11. With this variety of pre-emphasis settings, we are empowered to pick the optimal pre-emphasis setting to compensate for trace and cable losses.