Hi all,
In our case, when we did the Signal Quality Test more than once on a same board, the result is sometimes all the Signal Quality Test items passed, and sometimes signal rate failed .
USB 2.0 port work at USB2.0 HIGH SPEED and the processor is TI's DM3725(OMAP™3 ),USB transceiver is SMSC's USB3320. ,On the board, USB Differential signals Rout is short enough , and wire's Impedance match well .For getting the root cause ,we do the below test:
1, We test the Ti's OMAP™3 processor demo board (TMDSEVM3730) , on the board , USB transceiver is SMSC's USB3320 too .
Test result :we find their USB port has same issue ,Signal rate failed at times.
2,We change a new USB transceiver (TI's TUSB1210) on our console boards.
Test result is USB port has same issue ,Signal rate failed at times.
3, Change different test environment:Include oscilloscope,probe,USB Test fixture.
Test result :Signal rate still failed at times.
we guess the root cause is at USB host ----OMAP processor may have some shortcut at transmission speed, Do you have some suggestion.This issue is really urgent for us .
Attached are the kinds of Signal rate failed eye diagram .
Thanks&Regards
Peter