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Hi,
I have a prototype design with the USB hub mentioned in the title, configured as self-powered, non-ganged.
My issue is that I can't get the downstream ports to work since the !PWRON-signals stay high all the time. I already noticed that the power switches TPS2066D have active high inputs, thus the current configuration doesn't work. I replaced them with TPS2062 devices, which incorporate an active low logic at the input pins. As this didn't solve the problem my idea was that the power-up sequence is wrong (the low signal at the reset pin at power-up is too short). I inspected this with a scope, a screen capture is attached. The schematic is attached as well.
If you could take a look at the schematic and the power-up timing I'd appreciate it.
Thanks in advance!
Tim
Hello Tim,
I would recommend to adjust your initialization routine to comply with the datasheet recommendations:
"Reset with a pulse width between 100 μs and 1 ms is recommended after 3.3-V VCC reaches its 90%. Clock signal has to be active during the last 60 μs of the reset window"
Additionally, all USB DP/DM signal pairs require series resistors of approximately 27Ω to ensure proper termination. An optional filter capacitor of about 22 pF is recommended for EMI suppression. This capacitor, if used, must be placed between the hub terminal and the series resistor, as per section 7.1.6 of the USB specification.
Additionally all USB differential signals on the DS ports should have a 15k PD as specified on the DS and evaluation module schematics.
http://www.ti.com/lit/ug/sllu190/sllu190.pdf
