SLLA579 January   2022 ISOUSB211

 

  1.   Trademarks
  2. 1PCB Trace Insertion Loss and Inter-Symbol Interference
  3. 2Transmitter Pre-Emphasis and Receiver Equalizer
  4. 3Selecting an Optimal Pre-emphasis for Your System
  5. 4Eye-Diagrams for 6 inch to 4 feet Traces with all Nine Pre-Emphasis Settings for USB 2.0 Near-end Eye-mask
  6. 5Eye-Diagrams for 6 inch to 4 feet Traces and 5m Cable with all Nine Pre-emphasis Settings for USB 2.0 Far-end Eye-mask
  7. 6Using Receiver Equalizer and Transmitter Pre-emphasis for Channel Loss Compensation Simultaneously
  8. 7Summary

3 Selecting an Optimal Pre-emphasis for Your System

Eye-height (EH) and eye-width (EW) of an eye diagram are the two metrics used to quantify the signal integrity in an interface system. The USB 2.0 standard requires a USB device to comply with the near-end and far-end eye-masks. Hence, selecting an optimal pre-emphasis to compensate for your system trace loss will improve the eye width and eye height to meet the USB 2.0 eye-mask requirements. Figure 3-1 and Figure 3-2 show two ISOUSB211 placements for reducing the ISI caused by the insertion losses of the FR4 differential traces as shown in Figure 1-2 to comply with the USB 2.0 near-end eye-mask. These insertion losses can either be compensated using the transmitter pre-emphasis by placing the trace at the upstream of the ISOUSB211 as shown in Figure 3-1 or the receiver equalizer by placing the trace at the downstream of the ISOUSB211 as shown in Figure 3-2.

Figure 3-1 NE Setup 1
Figure 3-2 NE Setup 2