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TUSB321: Cable Connection Speeed

Trenton Vollendorf
Prodigy 20 points
Part Number: TUSB321

Tool/software:

Hi I am troubleshooting a circuit which utilizes a TUSB321 Controller to implement an UFP. I am leveraging OUT1 and OUT2 to only perform specific downstream device actions when a power source with 3.0A capabilities or better is attached. In short when OUT1 and OUT2 are low I know that the power supply attached can source the power my system will need. I am running into an issue where I have a power brick which can supply the 3.0A of current and it should be properly advertising this capability on the CC lines (which is read by the TUSB321 to set OUT1 and OUT2). I am noticing intermittent behavior by the OUT1 and OUT2 ports  (specifically OUT1 is not being pulled low as expected) when the USB power cable is attached. I've noticed that when I plug the cable in quickly to my device it nearly always works as expected. However when the cable is inserted slowly it nearly never works properly. I've measured the voltage at the active CC line and am measuring ~2.1V in both cases (fast insertion or slow). 

This is not something I was originally expecting. The datasheet does not indicate any timing parameters with regard to reading CC1/CC2 and setting OUT1/OUT2 (when configured as an UFP). Can you please help me to root cause and resolve this issue as intermittent operation is not acceptable for our product. 

FYI: Device Configuration

Pin1, CC1 = CC1

Pin2, CC2 = CC2

Pin3, CURRENT_MODE = No connect

Pin4, PORT = 10kohm pull-down to GND

pin5, VBUS_DET = 887kohm 1% pull-up to USB supplied power

Pin6, _vconn_fault = no connect

Pin7, OUT1 = 10kohm pullup to external power

pin8,out2 = 10kohm pullup to external power

pin9 = ID = no connect

pin10, GND = GND

pin11, DIR = no connect

pin12, VDD = VUSB or external power (depending on upstream device configuration)

  • 0 in reply to Trenton Vollendorf
    TI__Mastermind 39910 points

    Hi Trenton,

    I dont see any issues with the schematic shown. 

    How slow is the slow insertion? It may be possible that an additional resistance may be seen when the CC lines are first connected which would result in a lower current advertisement when the CC lines first connect. Have you tried this with another 5V 3A source?

  • 0 in reply to Vishesh Pithadiya
    Prodigy 20 points

    HI Vishesh, 

    I will admit that the insertion is quite slow to guarantee this behavior. However when inserting the cable at a normal speed the problem is much less frequent yet not mitigated entirely. 

    Creating a product where the user must continuously remove and re-insert a USB cable to get the desired functionality is not desirable. 

    Your point makes sense that during initial connection the CC lines may not present the proper voltage aligning with its intended advertising. Can you help me to understand what the timing characteristics are for this, to allow for a proper source to be specified? The datasheet does not indicate how transient voltages on the CC lines may affect advertising interpretation during initial device engagement.

  • 0 in reply to Trenton Vollendorf
    TI__Mastermind 39910 points

    Hi Trenton,

    The voltages required to be seen by the CC lines are as follows:

    These are the CC timing parameters:

    It mat be that the voltage seen by the CC controller is marginal between 3A and 1.5A and the timing of the plugging event results in a lower current advertisement. 

    Working under the assumption that the charger has a CC termination to 5V the thresholds are as follows:

    all the images are taken from the USB-C specification.

  • 0 in reply to Vishesh Pithadiya
    TI__Mastermind 39910 points

    Hi,

    I'm closing thsi thread due to inactivity.