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USB hosts hubs transceivers Forum Discussions

kekoc_4081231
Level 1
Level 1

Hi Cypress DevCommunity!

I am currently running into the following situation... Hoping that I can get some help on pinpointing the root cause.

When a device is hot plugged to the downstream port of the CY7C65642 Hub, the hub loses connection to the device and becomes very hot and dysfunctional.

The hub is using its internal VREG to supply +3.3V to VCC_D and VCC_A pins.

(After the hub gets hot and stops working) This scope plot is captured to show the +5V input to the Hub, the +3V3 from the Internal Reg, the PWR# and OVR# of the downstream port the device was plugged in to:

USBhubFried.png

I am also attaching the circuit schematics hoping someone may verify whether the design is correct or not.

Any input or comment is much appreciated!

Thank you,

Kenneth

Message was edited by: Ken Kong

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1 Solution
Sananya_14
Moderator
Moderator
Moderator
750 replies posted 500 replies posted 250 solutions authored

Hi Kenneth,

Based on the plots you have attached and the heating up of the hub, it seems like the device is drawing excess current due to a hardware issue and hence the hub cuts off the power after detecting the overcurrent from the power switch. Please monitor the VBUS on the downstream port from the power switch to check if the VBUS level is maintained. Please also try connecting a different device on the downstream port to see if the issue occurs.

For your schematic, everything looks fine. The PWR# polarity kept as active low is that correct?

Best Regards,

Sananya

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8 Replies
Sananya_14
Moderator
Moderator
Moderator
750 replies posted 500 replies posted 250 solutions authored

Hi Kenneth,

Based on the plots you have attached and the heating up of the hub, it seems like the device is drawing excess current due to a hardware issue and hence the hub cuts off the power after detecting the overcurrent from the power switch. Please monitor the VBUS on the downstream port from the power switch to check if the VBUS level is maintained. Please also try connecting a different device on the downstream port to see if the issue occurs.

For your schematic, everything looks fine. The PWR# polarity kept as active low is that correct?

Best Regards,

Sananya

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Hi Sananya,

Thank you for your comments.

The PWR# polarity is kept as active low.

I will try monitoring the 5V out and report back with further finding.

Is there any possibility for us to send in a failed sample for Cypress to investigate?

Look forward to your comments.

Regards,

Kenneth

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Hi Sananya,

For any unused downstream port, do the power enable and over-current pins need to be terminated?

If yes, what are the recommendations?

If no, can they just be left unconnected?

Thank you in advance!

Regards,

Kenneth

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Hi Kenneth,

Yes you could send over the failed sample for us to check.

For unused ports, it is recommended to connect the over-current pins to pull up resistors of 10K since those are input pins and optionally power enable pins to pull up resistors of 100K.

Best Regards,

Sananya

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Hi Sananya,

I have already created this...

Failure Analysis MyCase 00487737

May you please advise what the shipping address is for shipping over the affected product for analysis?

Much appreciated!

Thanks,

Kenneth

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Hi Kenneth,

The shipping address has to be mentioned by the FA team and is updated in the case. We will wait for updates from the case before further debugging.

Best Regards,

Sananya

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Hi Sananya,

Per MyCase #00487737, the failed unit has been received at the ChuNan facility.

I have referenced this page in the open case.

Thanks,

Kenneth

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Hello Kenneth,

As mentioned in the Failure Analysis Report, the damage was due to EOS and we recommend you to review your application and test conditions to prevent any power surge.

Best Regards,

Sananya

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