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TDA4VM-Q1: TDA4VM USB_VBUS design

Juanli Zhang
Intellectual 360 points
Part Number: TDA4VM-Q1

Tool/software:

Hi TI Expert,

I have some questions on USBn_VBUS interface. 

1. As you kmow the USBn_VBUS is used to monitor VBUS.   What will be the effected if I pull this pin to USB_3V3 wihch come from PMICB LDO2?

2. If the USB0 in host mode, who will provide the VBUS 5V?

3.Actually,  Our USB0 will be worked in both host and device mode.

    So if we had to generate 5V in our design? or If it is ok to bring in an always on 5V from an extenal device and connected the USB0_VBUS to USB_3V3 ? please see below picture.

The sch design of TDA4 as below.

BR 

Juanli Zhang

  • 0
    TI__Guru 59750 points

    Juanli,

    You can refer to our EVM for the Vbus implementation and use the Resistor divider network as suggested from the TRM.

    Depending on the Vbus and device ID pin, the SoC will identify if its in host mode or device mode. There is also an option where the Vbus would be connected even with the SoC is in device mode (eg. Car play).

  • 0 in reply to ShreyasRao
    TI__Mastermind 47530 points

    USB0_VBUS pin can handle 3.3v inputs - so no concern for damage. However - it is recommended to connect to VBUS rather than fixed PMIC supply.  (Note if connecting to 5V VBUS, a resistor divider is required as pin is NOT 5V tolerant.)

    In Host mode - typically the Host enables VBUS.  The signal USB0_DRVVBUS is recommended to enable the 5V regulator or switch to enable VBUS.

    The USB0_ID pin is used to select mode.  Host the ID should be pulled to GND, for Device mode pin should be left open/floating.

  • 0 in reply to Robert Eschler
    Intellectual 360 points

    Hi Robert,

    We use USB0.

    Q1: From TRM, USB0_ID is used to identify a/b devices. What is the A/B device?

    USB1_ID is used to identify HOST and Device.

    Q2: Based on the current HW design, we can use TDA4 as the HOST , and connect an external USB hub to expand the Ethernet interface for data transmission. Please note no matter in HOST mode or Device mode, the USB interface always has 5V power.

    If HOST the ID should be pulled to GND as you said, then it is strange why we can successfully expand the Ethernet interface through an external USB HUB?

    Q3: If we connect USB0_VBUS to USB_3V3, can we assume that the any external device complies with the USB specification?

    Q4: When TDA4 in host mode, what is the mechanism for VBUS detection?

    Thanks

    Juanli Zhang

  • 0 in reply to Juanli Zhang
    TI__Mastermind 47530 points

    Q1:  A/B refer to USB cable types.  In legacy USB systems, this also dictated USB roles.  With USB type-C cables now used, A/B cables are not used much any more.

    Q2:  The current implementation might be OK, but will require software changes on your end for how VBUS and/or ID pins are handled.  To use TI provided software as-is, recommendation is to follow our guidance for VBUS and ID connections.  What is the USB interface connecting to - a cable interface (thus connected device is unknown) or another on-board USB peripheral (device always known)?  If connecting to cable-type interface, I don't see how VBUS can always be powered (not aligned with USB specification)

    Q3: I don't understand question "assume that any external device complies with USB specification" - how does this relate to powering VBUS with USB_3v3?

    Q4:  In host mode, VBUS detection uses VBUS pin (if connected as recommended).  Note Host with use USB0_DRVVBUS IO to drive regulator to enable VBUS supply, processor would then detect VBUS power using VBUS pin.