TUSB2077A: How to configure those unused ports

Hi Brian:

  I followed your suggestion and left the unused pins(PWRON6,  DP6, DM6, PWRON7,  DP7, DM7) floating and pulled the OC pins(OVRCUR6,OVRCUR7) high.

  We found that there is a problem, the 5 ports that are in normal use are working normally, but there are some samples(about 70%) that will pop up the warning window "USB device not recognized", I suspect that it is caused by the two ports that are not used, is there a way to solve this warning?

Regards,

Eric

HI Eric:

  What status  is pin8? Did you configured as GANGed mode?

Best

Brian

Hi Brian:

  The status of pin8 is pulled up to 3.3V, and the following figure shows the local circuit diagram of 2077A

Regards,

Eric

Hi Eric:

  Do you  have schematic  for downstream ports? 

  Do you see any OVERCURR pi goes low? It seems pin 8 is hardwired to Vcc and can not set to low.

Best

Brian

Hi Brian:

  The problem has been solved by pulling the unused DP and DM feet low, thanks for your help.

Regards,

Eric

Hi Eric:

   Good to know issue was solved, Did you pull down DP/DM  with 15k or directly connect DP/DM to gnd?

Best

Brian

Hi Brian:

  Sorry for the late reply. I pulled the DP/DM down with a 15K resistor.

Regards,

Eric