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TUSB2046B: Chip not responding

Kinsey Fobes
Prodigy 80 points
Part Number: TUSB2046B
Other Parts Discussed in Thread: TUSB2036

We're migrating from a Tusb2036 to a Tusb2046 and the 2046 is not driving the DP0 line high in order for the system to detect its presence.  The clock is being generated and the voltages look good, but DP0 and DM0 are both low.  DP0 & DM0 don't appear to be heavily loaded (2.7 meg to ground)

Attached is a pdf of the circuit.

Any thoughts

KinseyUSB interface.pdf

  • 0
    TI__Guru 60870 points

    Hi Kinsey,

    I don't see the 1.5K pullup on DP0, is is located on another schematic page?  

    Regards,

    JMMN

  • 0 in reply to JMMN
    Prodigy 80 points

    JMMN

    Thanks for the quick response and good catch on the pullup resistor, I completely missed it.

    The Tusb2036 had a DP0PUR pin that the 2046 doesn't have.  Do I just pull the DP0 line to 3.3V and ignore the functionality that DP0PUR provided?

    Kinsey

  • 0 in reply to Kinsey Fobes
    TI__Guru 60870 points

    Hi Kinsey,

    Yes, you can connect the pullup to 3.3V, but you need to make sure that the DP pullup is not on when the upstream port is not connected.  It is not compliant behavior for a USB hub or device to source a voltage on DP or DM when there is no VBUS from the upstream port (host) provided.  If this is an embedded system, this is less of a compliance concern and you just need to make sure that the pullup on DP is not enabled before the hub can respond to the host.

    Regards,

    JMMN

  • 0 in reply to JMMN
    Prodigy 80 points

    Thanks

    Your help was both timely and concise.  Very much appreciated, you helped immensely!

    Kinsey