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TPS2561: Over current detection even at no load

kumar singh
Guru 10875 points
Part Number: TPS2561
Other Parts Discussed in Thread: TPS2560

Hi,

I am using TPS2561 for current limiting of USB Ports. TPS2561 enable input pin is controlled by Hub controller TUSB-4041I. Output is terminated to USB2.0 connector for sourcing current to external load which is very low load something like pendrive or optical mouse.' FAULT1 & FAULT2 pins are connected to overcurrent input pins of USB Hub controller.
I have designed for ILIM with 25.5K as current limiting resistor which should be much more than enough to drive external load up to 1A(Theoretically it should drive up to 2.4A).

 the Problem is whenever I connect any USB device to the Ports, TPS2561 gives overcurrent fault. Due to Over current fault detection, the Hub controller sets the enable inputs TPS2561 to low. I have tested by varying current limiting resistor R67(in above figure) to different values and all the time behavior is same for all range of resistors. I have checked the load current requirement by bypassing the input power from external source and found that load draws just 40-50mA which is much lesser load. But this much small load is also detecting as overcurrent by this IC which results in shutting down the output power of TPS2561.
Can anyone please tell what may be bug in the design? I have repeated this experiment in 3 boards and all behave the same. With external power, hub is able to detect the external USB device but with TPS2561, its not detecting.
Thanks.

  • 0
    TI__Expert 8420 points
    Hi ,
    It maybe logic control issue in the Hub IC. We suggest you to separat the device from your system (en, fault, vin ) use of an external 5V power supply to Vin and use a E-load/ resistor to debug . The another point is enlarge the input cap to invoide the input noise .

    Mike .
  • 0 in reply to Michael Tan
    Guru 10875 points
    Hi Michael
    I had tried to debug the issue by supplying vbus externally to the load and the port is detected. I have also found that hub is detected all the time. but when I connect vbus of load through tps.. it doesn't detect the port. I have observed another thing is when hub is not powered, tps... is enabled through pull up resistor available on enable pins. As soon as I connect hub to system, it pulls down the enable pin and tps... Doesn't give power to external port but hub detects in this case. When I connect power to output port externally, it gets detected but not when powered with tps..
    Regards
    Singh
  • 0 in reply to kumar singh
    TI__Expert 8420 points
    Hi Singh,

    You need to confirm the where the issue is come frome.
    Could you capture the waveform of TPS2561 for Vin, EN, Fault , Iout to analysis ? Are you sure the Iout have touched the over current limite level ?
    When we study the issue we need to assure the tps2561 is work well.

    Michael .Tan
  • 0 in reply to Michael Tan
    Guru 10875 points
    I will definitely share you waveform. But i would like to ensure that the output port is not overloading. I am using normal pen drive and mouse to test this which consumes around 50mA when powered through external source.
  • 0 in reply to kumar singh
    TI__Expert 8420 points
    HI Singh,
    Yes, I understand . We should find where to cause the Fault pin assert .
  • 0 in reply to Michael Tan
    Guru 10875 points

    Hi Michael,

    Here i have included waveforms.

    I have included waveforms for all the signals. "without hub input" are the waveform captured when hub input port was not connected. So by default enable input to tps...gets high due to pullup provided. Fault signal is high in all the case."with USB input" is waveform captured when load(pendrive) connected to output port. "with hub input" is waveform captured when hub was connected to system but output port not loaded.

    Regards

    Singh

  • 0 in reply to kumar singh
    TI__Expert 8420 points
    Hi Singh,

    I can't find any abmornal in your waveform. You mention the current have limit , If the current be limit the fault pin should set down and assert .
  • 0 in reply to Michael Tan
    Guru 10875 points
    Hi Michael,
    If you look into waveform above, you can see that as soon as USB hub is powered, it sets the enable pin of TPS.. low and output of TPS goes low. So when the HUB is powered, i am not able to get any output voltage on VBUS line of TPS... This is our problem. When we power HUB, Output port gets disabled. If output port gets disabled, how it can detect the port?
  • 0 in reply to kumar singh
    TI__Intellectual 2540 points

    Singh -

    Your design looks very much like the examples in the TUSB4041 datasheet (www.ti.com/.../tusb4041i).  I noticed though you have the PWRCTL_POL pulled down via R85 (4.7k). In looking at the 4041 datasheet, section 9.2.2.7 it seems this should be left unconnected (use internal pullup) so the PWRCTLx will be high assertion.

    "The PWRCTL_POL is left unconnected which results in active-high power enable (PWRCTLx) for a USB VBUS power switch..."

    Can you try depopulating this resistor?  It doesn't appear from your waveforms that the TPS2561 fault pin is asserting. Rather, I suspect the TUSB4041 is disabling the TPS2561 due to the polarity reversal.

    John

  • 0 in reply to kumar singh
    TI__Expert 8420 points
    Hi Singh,
    Could you also to choose the "Enable low active "device tps2560 to solve this issue ?
    You mention as the hub is powered , it will set the enable pin to low . tps2560 enable pin is low active .

    Michael .Tan
  • 0 in reply to John Perry
    Guru 10875 points
    Hi John,
    Your findings were correct. Since the PWRCTL_POL was pulled down so the HUB was setting the PWRCTLx pins low and this was disabling the Output power. I removed the R85 resistor and it solved the problem.
    Thanks for your suggestion.
    Regards
    Singh
  • 0 in reply to Michael Tan
    Guru 10875 points
    Hi Michael,
    TPS2560 is also good option.
    Thanks for your suggestions.