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TUSB8041: Wrong Enable output

Shawn_Wang
Expert 3811 points

Part Number: TUSB8041

Hi, team

After power-up (3.3V and 1.1V), the output wave of the Enable pin of TUSB8041 is shown bellow. 

In the customer's board, the 1uF capacitor is connected to the GRSTN pin(50pin). 

The power sequence has been modified to the sequence mentioned in the datasheet, but the output wave of the Enable pin of TUBS8041 is still not changed.

Can you identify what caused the wrong Enable output waveshape?

Thank you.

  • 0
    TI__Expert 3811 points

    After removed the pull-up resistor in the customer's board(like the R6 in the datasheet 9.2.1.2.2 Downstream Port 1 Implementation), the output of Enable (pin36) is stable and no jump occurred. 

    However, the removal of the resistor is relative to the lack of "Battery Charge support" according to the description in the datasheet, so the customer is concerned that this will affect the reliability of the system.

    Can you tell me what is the function of "Battery Charge support" of TUSB8041 and the effect on the customer's board if it lacks the "Battery Charge support"? 

    Thank you.

  • 0 in reply to Shawn_Wang
    TI__Guru 60870 points

    Hello Sidong,

    USB battery charging support is not required for normal USB operation.  It is an optional mode supporting special handshaking on the DP / DM lines to enable devices like tablets or phones to enter high current charging modes.  It should not be enabled unless the downstream port can supply 1.5A of 5V.

    Regards,

    JMMN

  • 0 in reply to JMMN
    TI__Expert 3811 points

    JMMN 

    Thanks for your reply.

    The downstream port is designed to 2A/5V on the customer's board. 

    Why occurred the process of the Enable output signal being pulled low when connected the pull-up resistor to the 3.3V supply?  You can refer to the following waveform.

    Look forward to your reply.

    For the 3.3V supply, 1.1V supply, and Enable output (36pin)

    Zoom in the ramp edge

    For the 3.3V supply, GRSTz, and Enable output (36pin).

  • 0 in reply to Shawn_Wang
    TI__Guru 60870 points

    I will close the E2E ticket since this is being discussed over direct email.

     

    The customer has configured the TUSB8041 as having active low polarity (PWRCTL_POL = L), but it looks like they have active high power switches.  Which is correct?

     

    The hub is driving the enable low to enable battery charging after power on reset.  I’m not sure why it is turning off, it may be getting configured by a host.

     

    What is occurring on the upstream port when these scope plots are taken?