SLLA642 July   2024 TUSB564-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2USB Type-C With DisplayPort Alt-Mode
    1. 2.1 USB Type-C Basics
    2. 2.2 Adding USB3
    3. 2.3 Adding DisplayPort Alt-mode
  6. 3USB 4-Meter System
  7. 4USB 9-Meter System
  8. 5DisplayPort 4.6-Meter System
    1. 5.1 5.4Gbps
    2. 5.2 8.1Gbps
  9. 6DisplayPort 9.2-Meter System
  10. 7Summary
  11. 8References

4 USB 9-Meter System

To simulate a long cable USB system, two 4.5-meter USB-C cables are used in the signal path. One cable is placed before the TUSB564-Q1, and the second cable is placed after the TUSB564-Q1. The bench board adds additional loss with it's short pre and post-channel FR4 trace. A USB-C host is connected upstream, and measurements are taken at the end of the downstream USB cable.

USB 9-Meter System Block Diagram Figure 4-1 USB 9-Meter System Block Diagram

For this test, the equalization setting used on the TUSB564-Q1 is setting #9. This adds 7.0dB of gain on the downstream facing port. Figure 3-2 shows the results of a 5G far end USB compliance test taken at the downstream end of this system.

USB 9-Meter System Test Results Figure 4-2 USB 9-Meter System Test Results

Once again, the 5G USB compliance test is able to pass in this configuration with no issues. The equalization from the TUSB564-Q1 is countering the added insertion loss from two 4.5-meter cables. This allows the eye to keep a defined shape as shown in the diagrams above. One thing to note is that there is a decrease in the differential output voltage between this test and the 4-meter system test. This is expected, as the TUSB564-Q1 is a linear re-driver which cannot alter the output swing of a signal. Tuning the output swing of the host can help to counter this if the application is expected to be long channel.