SNLA236 September   2015 DS125BR111 , DS125BR401A , DS125BR820

 

  1.   Linear Repeaters Used in SAS/SATA Applications
    1.     Trademarks
    2. 1 Introduction
    3. 2 SAS-3 Transmit Waveforms
      1. 2.1 Default Transmit Equalization Coefficients
      2. 2.2 Using Linear Equalization to Recover Tx FIR Information
      3. 2.3 Linear Equalization Effects on Jitter Due to Attenuation
    4. 3 Equalizer Placement within a SAS-3 Channel
    5. 4 System Results Using Linear Equalization
      1. 4.1 Linear Equalization Effects on Jitter Due to Attenuation
      2. 4.2 Channel Extension
    6. 5 Passing Out Of Band (OOB) Signals
    7. 6 Conclusions
    8. 7 Appendix A: Layout Considerations
  2.   Revision History

4.1 Linear Equalization Effects on Jitter Due to Attenuation

As shown earlier with the ability to recover and reproduce SAS-3 transmit FIR characteristics, this section shows a family of curves from the SAS-3 Transmitter and at the output of the DS125BR820 Linear Equalizer. As the SAS-3 waveform post cursor is stepped up from a minimum value (Light Blue Waveform), the DS125BR820 is able to stay in sync with the SAS-3 transmit waveform characteristics. Like waveform colors on left and right oscilloscope screens show SAS-3 Tx output and equalizer output characteristics for the same condition.

waveforms_sas3_tx_after_linear_equalizer_snla236.gifFigure 6. Waveforms at the SAS-3 Tx and After the Linear Equalizer

For this family of waveforms the linear equalizer was placed ~ 5 dB from the SAS-3 Tx. The waveforms taken at the output of the DS125BR820 utilized an equalizer setting of Level 2 (+5dB).