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XIO2001: XIO2001 not detected at all

Ahmet Cagri KIRISIK
Prodigy 70 points
Part Number: XIO2001

Hello,

We have a design incorporating XIO2001. It is derived from XIO2001EVM. Neither linux nor windows recognized this board. Please find attached scope screenshots consisting VDD3.3V, VDD1.5V, PERST, GRST and REFCLK. Power up sequence seems ok to me except the grst which is always deassertted if 3.3Vaux is present (which is present on PC pcie connector at all times?). And one odd thing is refclk- signal (also attached as a scope screenshot).

Since XIO2001 link is not active obviously, i was not expecting any PCI clocks from it but there exist a 11 MHz square wave from PCI_CLK0.

I am also attaching schematics, a review will be much appreciated. Thank you.

Regards.

(In this image, VDD_AUX (73) connected between 0.1uF cap to gnd and 1k to Vaux, after replacing 1k with zero ohm it grst turned to be 3.3V always).

XIO2001Sch.pdf

  • 0
    TI__Mastermind 35130 points
    Hi Ahmet,

    GRST# should be deasserted after the 3.3V and 1.5V supplies are stable. It looks like they are coming up at the same time in your system, which could be putting device in a bad state.

    Regards,
    I.K.
  • 0 in reply to Ikechukwu Anyiam
    Prodigy 70 points

    Dear Anyiam,

    Thank you for response. If you look closely to first image you will see grst doesnt start from zero volts. This is only possible if grst is internally pulled up to vdd_aux which is always present at motherboards pcie connector independent from power on/off conditions.

    And looking at refclk-, i thought maybe there is a pull up on refclk select pin and we may have selected 125 Mhz option in Error. Indeed there exists 1.2VDC(why?) at this pin but it is pulled down with 10k. Now after all this i am thinking maybe the pcb is faulty.

    Any thoughts? Thank you.

    Regards.

  • 0 in reply to Ahmet Cagri KIRISIK
    Prodigy 70 points
    Ok. I got the board working. It turned out to be a faulty soldering process where peak temperature exceeded PNP package specs by 70 degrees celcius. After replacing XIO2001 for the second time with correct method, it worked.

    About GRST, datasheet states that this pin is pulled up to VDD_33_COMBIO at all times, what i saw is as long as VDD_33_AUX is present -and aux power may be present in absence of 3.3V main power- grst is pulled up to ~2 volts. If this is the situation then you can not achieve the power up sequence as stated in the datasheet. I had to disconnect VDD_33_AUX from PCIe connector (B10) and bypass it with a capacitor.

    Thanks again.