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ONET1191P: data rate (Gbps) vs clock frequency (GHz)

B Luey
Prodigy 80 points
Part Number: ONET1191P

I'm confused about the clock frequency vs data rate for the ONET1191p. The datasheet says the part can go up to 11.3 Gbps operation, but the high-frequency 3db BW is as low as 8 GHz (and as high at 15 GHz). And the frequency response data in figure 3 only goes out to ~10.5GHz. Is the 11.3 Gbps data-rate based on dual-edge, so operating with a 5.65 GHz clock signal? Or is it single edge and even though the 3dB point can be as low as 8 GHz, the device can still operate within spec for data-rates with a clock up to 11.3 GHz? If so, shouldn't figures 3, 5 and 6 go out to at least 11.3 GHz? Or am I not thinking about data rate (Gbps) / clock rate (GHz) correctly?

Thanks,

  • +1
    TI__Guru* 93670 points

    Hi Benjamin,

    11.3Gbps Nyquist frequency is about 5.6GHz. At this frequency, we have main signal strength. When using a spectrum analyzer, we see a resonance at this frequency. ONET1191P 3-dB bandwidth is at minimum 8GHz - well over 5.6GHz. So we are able to recover main energy and beyond.

    In summary, we need to have a bandwidth higher than Nyquist frequency. At the same time, this bandwidth should not be too high since this can increase jitter.

    Regards,Nasser