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TUSB2077A with a TPS2043B

Colin Dawson
Prodigy 180 points
Other Parts Discussed in Thread: TUSB2077A, TPS2043

I am having a rough time having my microprocessor initialize any device using the TUSB2077A embedded on my board.  Any chance someone can look at my layout to tell me what I am doing wrong.  I utilize the TPS2043 for power.  I have read the application note and the other forums on this chip.  I'm running out of ideas.  Thanks in advance.

  • 0
    Prodigy 180 points

    8473.USB Circuit.pdf

    Here is my schematic.  Please take a look.

  • 0 in reply to Colin Dawson
    TI__Mastermind 36085 points

    Hello Colin,

         I just reviewed the schematic and I found an issue, the RESET must be asserted during a power cycle and an upstream connection, please make sure that  U8 has a similar behavior as the circuitry marked with red on the attached document.

    Best regards,

    Diego.

    4885.TUSB2046-PlainSelfPower.pdf

  • 0 in reply to Diego Cortes
    Prodigy 180 points

    I'll check it out thanks for the suggestion.  I should know soon.

  • 0 in reply to Colin Dawson
    Prodigy 180 points

    After I initialize the USB in my Microprocessor, I use a GPIO pin to RESET(Logic Low) the TUSB2077 chip for 250usec verified by oscilloscope.  So I removed R112 and C112 from the attached drawing and connected RESET to U8.  Is this an acceptable way to handle the RESET line? Obviously the TUSB is still not recognized.  So I still have a problem.

     I removed the pull down resistors (R116 and R115) on my PWRON lines after realizing they are push-pull.  I have 3.3V on OVRCUR which is good, but the 3.3V on PWRON isn't letting 5v get to my device through the TPS2043.  It looks like the TUSB isn't configured.  HUBCFG is low (0V).

    Any off the shelf hub plugs into the same USB lines and works.  These chips should just work correct?  No programming required?  Any comments are appreciated! 

     

     

  • 0 in reply to Colin Dawson
    TI__Mastermind 36085 points

    Hello Colin,

         THe HUBCFG is low because the TUSB2077 is not being properly initialized, I mean that the reset sequence is not asserted (this device does not requires any extra configuration). You mentioned that You are Using a GPIO pin to activate the RESET terminal, with a pulse tied to low during 250 us (this timing is OK) but my concern is about the power on sequence. Are You sure You are asserting the RESET terminal before the VCC signal reaches the 90% and the clock signal is active during the last 60 μs of the reset window?

    Regards,

    Diego.

  • 0 in reply to Diego Cortes
    Prodigy 180 points

    Diego,

    I really appreciate your quick response.  I totally missed what "asserted at power up" meant.  Yes my power on sequence is wrong.  Ugh!  What a dumb mistake... My clock signal (aka 6MHz Crystal) is set up like other examples.  I'm off to hopefully get this resolved and will update probably tomorrow.

    Thanks

  • 0 in reply to Colin Dawson
    Prodigy 180 points

    Diego,

    I was able to get the hub chip to work after powering it up properly. HUBCFG is high. Now, I have to work out how to keep that consistanly happening, but that is my problem. :) I found devices only initalize on DP and DM 1-6 of TUSB2077. Trying to utilize the TPS2043 OUT3 in conjunction with DP and DM7 on the TUSB2077 isn't working.  It appears the PWRON7-EN3 lines stays high keeping OUT3 from sending 5v to my device.  OVRCUR7 is high.  Is there another obvious thing I'm doing wrong?