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USB Hosts Hubs Transceivers

Anonymous
Not applicable

Hi,

I am using CY7C65642 in my design along with CYPD-3120 and external USB device. During platform testing i see USB device stop responding if USB-C cable length is varied.

I bypass CY7C65642 and retested with same same USBC cable and then USB device start responding. With this experiment i am thinking is CY7C65642 introducing an side effect to see this behaviour. 

Do CY team has any such case study to confirm the limitation with CY7C65642 and probably alternate solution.

Thank you,

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1 Solution
Moderator
Moderator

Hello Arun,

The recommendation for shorter cable length is because even though USB spec says 5m, it is only the maximum length and in case there is signal degradation on your board or on the host side, it will be preferred to keep it lesser than that. Please let me know- the data signal trace length, width. the air gap between the traces, and if there are any vias on the lines.
However, if you are using an active cable, please check if VCONN is enabled and the cable is re-driving the data using an analyzer. If it is, then using a 18 ft cable should not be an issue.

Best Regards,

Sananya

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Moderator
Moderator

Hi,

Could you please attach your schematic for our reference? The cable length should be within 5 meters as per USB 2.0 Spec.

Best Regards,

Sananya

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Anonymous
Not applicable

Hi Sanm,

complete sche can't be done its restricted. Spcific part is shown below. You can suggest for any change.

Thank you,

pastedImage_0.png

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Moderator
Moderator

Hello,

-Could you please provide a block diagram showing how the CY7C65642, CYPD3120 and external USB device are connected?

-Is the CYPD3120 used for power delivery?

-Also, is there any particular length of the type-C cable after which you dont see the device enumerating?

-Does this occur for other downstream devices as well?

Regarding the current schematic I hope you have set a RESET period of atleast 5 ms and there are pull up resistors on your I2C lines.

Best Regards,

Sananya

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Anonymous
Not applicable

Here is the block diag

pastedImage_0.png

Power will be delivered from USB-C UFP device over USBC cable.

With 6ft USBC cable things are ok, later i will extended the cable using one more M-F USBC cable of 6ft .

If i used this USBC cable+M-F cable with other host using USBC to USB 2.0 adapter from cypress than keyboard/mouse responds. length(Host to device) is around 6+6+4+2ft = 18ft.

I am having a customsied DP and USB2.0  to USBC hub to test above usecase

Do you see/suggest anything below your observation? pl suggest.

RESET period of atleast 5 ms

pull up resistors on your I2C lines.

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Moderator
Moderator

Hi,

-Please use a shorter type C cable to ensure a total length of less than 4m on the upstream port i.e. between host and hub, the current length is almost 4.8 m. Are you using USB-IF certified cables?

-Please mention if you are using an active or passive type C cable.

-If you are still facing issues with the hub connected but not with the device directly connected, kindly send us the layout files over private message option if possible.

Best Regards,

Sananya

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Anonymous
Not applicable

Hi Sananya,

I tested using short USBC cable and USB device is responding. 

USBC cable are customized cable supplied by  Amphenol and cables are as per standard and its Active cable type.

I can share on layout,pl let me know the email.

Thank You,

Arun

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Moderator
Moderator

Hi Arun,

Kindly share your schematic and layout over private message and we can check if anything can be improved.

Best Regards,

Sananya

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Anonymous
Not applicable

Hello Sananya ,

As I informed you earlier, we are having an NDA with our customer so, not

able to share complete layout,schematic.

Attaching snap shot of layout around USB 2.0 D+/- passing through

CY7C65642 marked as U1522 from edge connector J18 to J9.

Please let me know do i need to highlight any other tracks.

Thank you,

Arun

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Anonymous
Not applicable

Hi,

Do you have any update for me. I shared specific area of layout and schematic snaps.

Need to check with you about Dec 4 discussion on USB cable length. You mentioned it should be less than 4m. But as per USB spec it can be 5 mts right?

Pl let me know,do you have any other cypress soultion in which i can acheive USB 2.0  communication greater than 5 ft

Waiting for you reposne.

Thank you,

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Moderator
Moderator

Hello Arun,

The recommendation for shorter cable length is because even though USB spec says 5m, it is only the maximum length and in case there is signal degradation on your board or on the host side, it will be preferred to keep it lesser than that. Please let me know- the data signal trace length, width. the air gap between the traces, and if there are any vias on the lines.
However, if you are using an active cable, please check if VCONN is enabled and the cable is re-driving the data using an analyzer. If it is, then using a 18 ft cable should not be an issue.

Best Regards,

Sananya

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