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Power On Reset design issue with TUSB2046B

Duon Foung Foo
Prodigy 150 points
Other Parts Discussed in Thread: TUSB2046B

I have problem posting my progress on my old TUSB2046B "USB Device Not Recognized" Design Issue discussion forum.

Thanks Anton Egorov for pointing out my mistakes. I've made the correction to the DP and DM to D+ and D- connections. I was hopeful my USB hub should be working properly now but when I connect to my PC with thumb drive by running the USBview debugger at the same time, the USBview debugger show no USB is connected.

Texas Instruments recommends a minimum of 100 μs to a maximum of 1 ms of reset timing. By the way, I've monitored that the crystal oscillator is running at 6MHz on oscilloscope. It seems that the reset timing is very critical to the USB operation, so I experiment it by replacing the 15K resistor with a 200Kohm trimmer, with capacitor remains at 100nF. Below are the timing diagram from different trimmer settings :
The Ch 1 signal (Yellow) is the +3V3 signal.
The Ch 2 signal (Blue) is the XTAL1 signal.
The Ch 3 signal (Purple) is the Reset signal.
The Ch 4 signal (Green) is the Suspend signal.

1st trimmer (lower resistance) setting:

2nd trimmer (higher resistance) setting:

Even with the above different trimmer settings, I still could not get my USB hub recognized by by PC. From the above picture, it seems that the crystal only starts oscillate 2.5mS after VCC is applied, this is definitely longer than the recommended reset time of 1mS, If I adjust my trimmer to faster reset rise time, the crystal has not even oscillate yet (Picture 1). On the other hand, if I adjust my trimmer to slower reset rise time, the Suspend line will goes high after 10mS (Picture 2).

Any thing else should I try to correct this TUSB2046B "USB Device Not Recognized" problem?

Anyone one with working TUSB2046B USB hub would like to share your experience? Thank you very much.

  • 0
    TI__Guru* 76130 points
    Hello,

    The datasheet says: ".... Clock signal has to be active during the last 60 μs of the reset window..."
    The time scale is too large to see the detail but it doesn't look like you are meeting that requirement.
    The clock signal on your scope capture is about 300Hz

    Regards
  • 0 in reply to Elias Villegas M.
    Prodigy 150 points
    Hello,

    There is a problem monitoring this 6Mhz signal with the reset time using oscilloscope. The oscillation signal shown on the scope with slower timebase of 5mS/div will appears to be oscillated at slower frequency. But if you were to monitor the oscillation signal by itself, the signal is oscillated at 6MHz.

    Based on the scope signals I captured so far, it does seem that the crystal only starts oscillate 2.5mS after VCC is applied, how do I overcome this problem? Any idea how should I proceed from here?

    Thanks and regard,
    Foo DF.
  • 0 in reply to Duon Foung Foo
    Prodigy 150 points

    I've retaken the signal waveform using Agilent oscilloscope.

    The Ch 1 signal (Yellow) is the +3V3 signal.

    The Ch 2 signal (Green) is the XTAL1 signal.

    The Ch 3 signal (Blue) is the Reset signal.

    The Ch 4 signal (Purple) is the Suspend signal.

    1st trimmer (lower resistance) setting:

    2nd trimmer (mid resistance) setting:

    3rd trimmer (max resistance) setting:

    From the above pictures, it is clear that the crystal start oscillates 2.5mS after VCC is applied, this is definitely longer  than recommended reset time of 1mS

    How do I overcome this problem? Anyone one with working TUSB2046B USB hub would like to share your experience?

    Thank you very much.

    Regards,
    Foo DF.

  • 0 in reply to Duon Foung Foo
    TI__Mastermind 18655 points
    Hello,

    The last scope capture shows a peak to peak voltage of 4.6 V on the +3.3V signal. The maximum recommended voltage for this device is 3.6. Could you check if Vcc is following this requirement.?

    Are you able to test the TUSB2046B with a different host and reproduce the issue, also try another USB device ?

    Can you use the USBView and take a screen shot for me?

    Could you provide some trace captures using a USB protocol analyzer between the host and the TUSB2046B?

    Regards,
    Joel
  • 0 in reply to Joel Jimenez0
    Prodigy 150 points

    Hello Joel,

    Thanks for replying. The Vcc is measured at 3.32V using multimeter.  I don't have USB protocol analyzer in my workplace.

    I did run the USBView debugger when I connect the USB Hub to my PC, the USBView shows nothing.

    From the previous posting, it is clear that the crystal start oscillates 2.5mS after VCC is applied, this is definitely longer  than recommended reset time of 1mS

    How do I overcome this problem? Anyone one with working TUSB2046B USB hub would like to share your experience?

    Thanks,
    Foo DF.

  • 0 in reply to Duon Foung Foo
    TI__Mastermind 18655 points
    Hello Foo DF,

    What is the failure rate (# of units failing/# of units tested)? Device swap need to be done to see if the failure follows the device.

    Regards,
    Joel
  • 0 in reply to Joel Jimenez0
    Prodigy 150 points
    Hello Joel,

    Thanks for the reply again. I only soldered 1 board to try out the functionality.

    I'm still waiting for reply on how to overcome the crystal start oscillates 2.5mS after VCC is applied problem.

    Any suggestion on how I should proceed?

    Thanks and regards,
    Foo DF.