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TUSB2036: USB HUB -> FTDI chip no signs of life

Bob Shankle19
Intellectual 265 points
Part Number: TUSB2036

Hi Folks,

This is my first time using the TUSB2036 chip, but have used the FTDI chips before in my design.  I'm not seeing any signs of life (nothing registering or trying to register when I connect to a PC or RPI device.)

Is there a driver for the TUSB2036 that I can use to see if it reaches the EEPROM on this device?

I am only using 2 of the 3 downstream connections.

thanks,

Bob

ps I'm glad to provide a larger schematic with the FTDI chip but wanted to make sure I wasn't missing something with the hub first.

  • 0
    TI__Expert 7395 points
    Hello Bob,

    You need to add a 1.5K resistor to the XTAL2 terminal to trim the gain. Please refer to figure 5 at section 8.3.2 on the device's datasheet.

    Additionally, you also need to place a 1.5K resistor between DP0PUR and DP0; and all USB DP, DM signal pairs require series resistors of approximately 27 ohms to ensure proper termination. An optional filter capacitor of about 22 pF is recommended for EMI suppression. This capacitor, if used, must be placed between the hub terminal and the series resistor, as per section 7.1.6 of the USB specification.
    Please refer to figure 9 at section 9.2.2 in the datasheet.

    Please try it out and let me know how it goes.

    Regards,
    Jorge
  • 0 in reply to Jorge Llamas (SWAT)
    Intellectual 265 points
    Jorge,

    Thanks for the reply. Since the board is going to need some manual rework, which of the items above would have the highest probability of being the problem on not seeing the device in Windows Device manager. (I'm think the EMI items I can catch on the next board respin, but the two 1.5K resistors are probably what I need to add on the board before I see anything come alive.)

    Thoughts?

    thanks,
    Bob
  • 0 in reply to Bob Shankle19
    Intellectual 265 points

    Hi Jorge,

    I made some of the changes, windows now responds with:

    "Unknown USB Device (Device Descriptor Request Failed)"

    Are there any tools I can try using to program the eeprom with the correct device id or a way to tell Windows what it is (for example is there a driver available that I can assign?)

    thanks,

    Bob

    (I realize there is a good chance it is still hardware related on my end but wanted to check.)

  • 0 in reply to Bob Shankle19
    TI__Guru 60870 points

    Hi Bob,

    You will also need a capacitor of ~1uF on the RESET/ pin otherwise the TUSB2036 doesn't get a power on reset and probably won't function.  That capacitor and the 1.5K pullup on DP / DP0PUR that Jorge mentioned are the two most important circuit changes to get the hub running.

    Regards,

    JMMN

  • 0 in reply to JMMN
    Intellectual 265 points
    Thanks! I couldn't find the 1uF cap requirement in the datasheet. (Reply with section number if it is in there, otherwise I'll figure this is just general practice.) thanks again, Bob
  • 0 in reply to Bob Shankle19
    TI__Guru 60870 points
    The datasheet only calls out that the reset needs to be pulsed low at power on reset , but it doesn't give specific passive circuit information. The 1 uF is from the reference schematics.

    Regards,
    JMMN
  • 0 in reply to JMMN
    Intellectual 265 points

    Hi JMMN,

    I went through the schematics in the datasheet and didn't see the cap.  Can you attach the reference design to this thread?

    Also, having the EEPROM in my design, is that helping or hurting since it is also hanging on the /reset line.

    thanks,

    Bob

  • 0 in reply to Bob Shankle19
    TI__Guru 60870 points
    Hi Bob,

    Reference schematics are here: www.ti.com/.../getliterature.tsp and all docs for TUSB2036 are here: www.ti.com/.../technicaldocuments

    Having EE_CS connected to the TUSB2036 is ok as long as it is driven low for a sufficeint period of time to generate a power on reset and then stays high.

    Regards,
    JMMN