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USB Hosts Hubs Transceivers

electrofabio
New Contributor

Good morning everyone,

I'm trying to develop a small board using a 2-ports HUB CY7C65634-48AXC.

At the moment there are no downstream devices connected to the HUB ports, i'm just focusing on getting the HUB device itself up and running.

As a clock source I'm using a programmable oscillator set to 12 Mhz; clock source selection inputs of the Hub IC (SEL48/ SEL27) are connected according to the datasheet specs (both input pulled up to logic "1").

What I see is the following: when I try to plug the board into a windows PC, the device is not enumerated and recognized:

"The last USB device you connected to this computer malfunctioned, and Windows does not recognize it."

If  I look at the board with a scope:

  1.  Power rails are OK;
  2. When I plug USB into the PC, some transactions are visible on D+/ D- USB lines for about 2/3 seconds;
  3. Something strange happens on the CLK line: after 2/ 3 seconds from the startup, the signal amplitude gets lowered (around 2.8 V instead of 3.3 V); also, if I check the XOUT pin on the Hub IC, I can see a 12 MHz signal at the very beginning, but with a "slow" rising slope,then the signal get become a continuos 3.3 V.

 

Do you have any hint on what I can check in order to isolate the issue? I've already double checked the schematic and everything seems fine and according to the Datasheet requirements.

Thanks in advance,

Regards,

Fabio

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1 Solution
MallikaK_22
Moderator
Moderator

Hello Fabio,

Please check the following application note on hardware guidelines.

Regards,

Mallika

Mallika

View solution in original post

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1 Reply
MallikaK_22
Moderator
Moderator

Hello Fabio,

Please check the following application note on hardware guidelines.

Regards,

Mallika

Mallika

View solution in original post

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