TUSB2046B: TUSB2046B Enumeration Problem

Hi Mike,

Does the hub get loaded in addition to the 4 unknown devices? Are the 15K pulldowns at the downstream connectors?

Please check: power , clock, suspend output and if downstream port power is enabled.

Regards,
JMMN

There are no downstream devices connected to the 4 ports - they are all open. There are certainly the 15K pulldowns - attached is the schematic for the USB connectors. Power and clock looks correct. SUSPND is Low. All 4 PWRON outputs are low (ON), and there is 5V on every port.

Hi Mike,

Ok, the schematic looks clean. It sounds like the schematic and layout have not changed, just the vendor. Is that correct? If so, I would check if there is a good thermal pad connection and if the right resistors are populated. If there is a 1.5K pulldown instead of a 15K pulldown, or something similar that could cause major issues. Can you post a screen grab of Device Manager when the hub is connected?

Thanks,
JMMN

Here is a screen capture of the Device Manager - there are 4 Unknown Devices that correspond to the hub. The popup is from double-clicking the first one (but all look the same).

Hi Mike,

This doesn't correlate to any of the usual USB hub bring-up issues. Are you seeing 100% fall out? The schematic looks fine, so it looks like something is not assembled correctly.

Can you download usbview.exe from Microsoft so we can see what if any descriptors are reported? It runs a lot like Device Manager but reports more USB data.

Thanks,
JMMN

I have tested 5 out of 100 boards and they all behave the same. Attached below is the USBView capture of the Hub descriptors - there are 4 devices under the Hub that show as Unknown Devices - all fields for those 4 devices are zeroes.

The only part change I know of from the last board to this was to change the Bulk capacitors on the 5V outputs of the TPS2044 from 100uF to 33uF - would this have any of this sort of affect?

It appears something on the downstream DP/DM lines is being detected as a device connect. Try ohming out the connections and making sure the ESD devices are placed properly.

Regards,
JMMN

The ESD device does seem to be the issue - if I remove those the ports all work. However, it is the correct part (Littelfuse SP3003-02XTG) and it does seem to be assembled correctly.  What parameters of this ESD pack could cause a symptom like this?

Thanks,

Mike