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TI TUSB7340 USB Port disable and Power Consumption

Jean-Charles
Prodigy 80 points
Other Parts Discussed in Thread: TUSB7340, TUSB7320

Hi,

I have couple issues with TUSB7340. I am able to establish communication through the PCI Bus. I got the power sequence and the clock right, I am able to see the USB hub Running Linux. However When I connect a USB Key I don't see the key. 

I did some trouble shooting and I found that the Over Current pin needs to be taking care for it to work (I've tested it on . According to the datasheet the Over current pins are internally pulled up, so on my design I left them floated since I didn't need them. But It turns out  that the Overcurrent controls the PWRON pin and that seems to control the USB data bus. 

What I have done on the Eval Board (TUSB7320 Eval Brd) and on my board is driving the OVERCUR pins High and low and see what I get. On the Eval board When the OVERCUR is High then PWRON is low and I can Read/Write to the USB Key. When the OVERCUR pins are LOW then PWRON is high then I can read/write to the USB Key. 

However on my board since I didn't initially use these signals, I had to lift the chip of the board and shorted the the OVERCUR pins to 3.3V. I did that on all 4 ports but the PWRON pins stays high, and they don't go low regardless of what I do with the OVERCUR pins (High or Low). I can't read/write to the USB key on any port. 

I am out of option at this point not sure what else to try. I don't understand why it's not working, since I have access to the registers through PCI, i tried getting some satus, but no fault detected. 

I also noticed that I'm consuming power more than what I expected from this chip when it's in idle. It also gets hot to the point that I'm considering of applying an heat sink. I Notice from the TUSB7320 does not get hot. I am pretty confident that i am handling thermal dissipation well, I have a ground plane, and 18 Vias connected to GND on the thermal PAD. 

Based on other people posting online about the power consumptions issues, I have a feeling that it's not necessarily something I'm doing wrong and I suspect the chip itself. why is it not consuming the Could it be because it's a 4 port? instead of 2? Is there anything else I can do to handle the heat other than adding an heat sink? I'm trying to avoid heat sinks in my design...

I really need the USB port to works ASAP, I'm hoping that I can get it to work on my current board, while I'm working on another revision of my board, but so far this issue doesn't inspire me confidence unless I can find a way to fix it. Is there anything else I can try to enable the port? 

Regards,

JC 

  • 0
    TI__Guru* 76130 points
    Hello,
    How reliable is the re-work you did(lifting the device and shorting OVRCUR#) ?
    Do you have a board without this re-work? Does it get hot?
    Can you share your schematic for review?
    This device does not need heat sink if the powerpad is properly grounded.
    Because of the package of this device it is probably you have some soldering issues after the rework.
    Are you able to do some x-ray to your board?
    Regards
  • 0 in reply to Elias Villegas M.
    Prodigy 80 points

    Hi 

    I had the rework done by professionals, although I admit it is not the idea testing case, I have to say overall the rework is pretty reliable. 

    I am using 4 ports but I am mainly concern for port 3...For the port 3 and 4 the over current pins is only accessible underneath the part (Pin B43 and B45), for these pins, the chip was lifted and we used a very small wire to connect them to 3.3v (Pin A47 which was closest to them...) we later confirm with an X-ray that the connection was there after the part was placed, to make sure all the pins were aligned and that the connection was still there. 

    However for port 1 and 2, the over current pins is accessible from the outside of the chip and the part doesn't need to be lift to access them...For these ports I solder a wire from A36 and A37 and connected to 3.3V and GND to see what would be the status of the Power ON pins on these ports...but there was no change on the PWRON pins, it always stayed high (3.29V) therefore not allowing communication through the port...

    The point is I shouldn't even have to do that mod, because in theory according to the datasheet, there are internal Pull up on these pins, so by default the chip should be on "Over Current not detected mode". Since it wasn't working the mod was added as an attempt to solve the problem. 

    I understand that this device does not need and heat sink in theory, however before the re-work was done the device was getting hot. and I was getting an additional 1.2W than I expected. It almost looked to me that all the ports were active because in theory because when all ports are active it should be about the same power consumption 1.3W. However but the port were not active because the PWRON pins on all port was High and it doesn't recognize any usb Key... 

    The thermal issue is similar to what was reported in this post: (See below). I really doubt that it is related to the issue that I am having with the ports because based on what I read from these post, even when the USB ports are working it gets hot, also people reported to have hot on idle too...I am pretty convince that I followed guidelines on how to handle the thermal dissipation. Like I said before I have a ground plane ad well as 18 vias connecting the thermal pad to ground...

    For now I'm really trying to focus on getting the port to work, and I was wondering if there are anything else other than triggering the Over current pins high and low that I can try, before I redesign my board? I just don't want to redesign my board to incorporated all the changes that I've noticed just to realize that I still have the same issued with the ports. So I would feel more comfortable if I could get them to work before I redesign...

    Is there an email that I can forward print screen of the schematic? or Layout if necessary? I can't figure out how to copy a picture in this post...