I've made a custom usb hub with CY7C65632, and it has got some overcurrent issue on downstream pp

[kayip]

Hi!

I'm made a custom usb hub for my wearable device project.

I modified the reference schematics for CY7C65632-28PIN, and one depth cam and one audio card is attached to the hub.

Unfortunately, I missed out the fact that the depth cam needs 120mA. so when it is attached to the hub, windows reports insufficient power supply. 

Here is my schematic.

I've tried to disconnect FLGA, FLGB of external power switch(AIC1526-0), which is connected to OVR_#_[1], OVR_#_[2] ofCY7C65632 to avoid to notify overcurrent situation. but seem like it doesnt work. Windows still give a insufficient power supply warning message.

Is there any way to avoid this situation?  

Also,  I also tried to power the depth cam with external power supply, and still connect DM, DP to the hub. and it seems like the hub controller shut the port. so the depth cam is still not recognised. 

Does the USB controller chip shut usb signals when the device doesnt request the power from the hub?

Best, 

WOOJUN

[Sananya_14 · Accepted solution]

Hi Woojun,

Since your design is bus-powered, the maximum allowed power on each port is 100mA and since the depth cam is requesting for 120mA through its descriptors, the host is shutting off power for the port. This is done even before the power switch reports overcurrent based on the set limit.

As you have mentioned, making the design self-powered using external supply will allow upto 500mA on each port. But this needs to be configured in the hub descriptor using the SELFPWR pin. So please connect the pin to VCC using a recommended 100K pull up. Please note that in this case the hub shuts off power for the ports based on the command from the host i.e. when the host displays the "insufficient power" message.

Best Regards,
Sananya