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USB hosts hubs transceivers

electrofabio
Level 1
First question asked Welcome!
Level 1

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 250 solutions authored 500 replies posted 250 replies posted
Moderator

Hello Fabio,

Please check the following application note on hardware guidelines.

Regards,

Mallika

View solution in original post

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1 Reply
MallikaK_22
Moderator
Moderator 250 solutions authored 500 replies posted 250 replies posted
Moderator

Hello Fabio,

Please check the following application note on hardware guidelines.

Regards,

Mallika

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