SLLA613 august   2023 TUSB1146

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Test Description
    1. 2.1 Equalization Configuration
    2. 2.2 Eye Test
    3. 2.3 BER Test
    4. 2.4 Alternative BER Test
  6. 3Test Results
  7. 4Summary
  8. 5References

2.4 Alternative BER Test

As mentioned in Test Description, the following test is recommended for designers that want to reproduce test results for comparing AEQ with static EQ.

The alternative test gathers JTOL measurements for a given channel. This test requires that the BERT outputs the test pattern through the ISI channel board to be received by the TUSB1146 through a connected breakout board at the receiver. The TUSB1146 can equalize the signal through static EQ or AEQ, and retransmit the signal to a connected SuperSpeed USB device (labeled DUT). The DUT then loops the pattern back through the breakout board transmitter to be gathered by the BERT.

GUID-20230718-SS0I-ZB37-N3NK-8BJNSH42RN9B-low.svg Figure 2-3 Alternative BER Test Setup

Because this test utilizes the TUSB1146EVM, there are several minor modifications to the previous procedures. The first modification is that this test has loss at the TUSB1146EVM transmitter due to the cable connecting it to the DUT. The TUSB1146 does need to be configured to run in limited redriver mode to compensate for potential losses between the DUT and EVM. Please see the TUSB1146 data sheet for configuration instructions. The second modification is that this test utilizes USB-IF compliance software provided by Keysight®, LeCroy®, and other oscilloscope brands. The USB-IF compliance software automatically runs compliance tests detailed by the USB-IF specifications board. This test utilizes a USB Type-C SuperSpeed (5Gb/s) Rx Short Channel Jitter Tolerance test to gather data, which runs automatically through BERT software. Because of the altered test setup, results obtained from the tests in this document cannot be used as official USB compliance results.

For more information about the description of this test, guidelines for manual performance, or details about patterns or specifications, see also the Electrical Compliance Test Specification SuperSpeed Universal Serial Bus Revision 1.0a and other related USB-IF documentation.

Alternative BER Test Procedure:

  1. Configure the hardware setup in Figure 2-3, and turn on all devices.

  2. Select a channel length for the trial and modify the ISI channel board.

  3. Configure selected EQ type as described in EQ Configuration.

  4. Run the 5G Rx Short Channel Jitter Tolerance Test.

This procedure produces a graph showing the maximum tolerable jitter level for a given frequency before producing major bit errors (1E-10).