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TCI6638K2K: USB 2.0/3.0 Interfacing with +3.3V eUSB Module

Remya Nellikkal
Prodigy 70 points

Part Number: TCI6638K2K

Hi,

We want to interface TCI6638K2K with an eUSB module which is +3.3V with a 10pin header (having all the USB2.0 and USB3.0 signals and +3.3V power pin).

USBVBUS is a +5V, analog input for monitoring the voltage on VBUS. In this case the VBUS is 3.3V since the USB Device is +3.3V. So can we connect +3.3V to this pin instead of +5V in this case.

Please confirm.

Thanks and Regards,

Remya

  • 0
    TI__Mastermind 37500 points
    Hello
    Section 6.13 of the Keystone II Hardware Design Guide (sprabv0) shows the needed connections and voltage levels for USB 2 and USB3. I would follow these connection examples.
    Regards,
    Joe Quintal
  • 0 in reply to Radio-Joe
    Prodigy 70 points

    Hi Joe,

    We have referred the same manual in which "Table 26 USB Control Signals", USBVBUS (VBUS comparator voltage pin) 5V analog input for monitoring the voltage on VBUS. Please let us know the comparator reference voltage.

    We need to use VBUS as 3.3V (Since the eUSB which we are using is 3.3V device), so if we monitor VBUS using the pin USBVBUS, will it always be giving a fault condition? What is the voltage level after that it gives a false alarm?

    Thanks,

    Remya

  • 0 in reply to Remya Nellikkal
    TI__Mastermind 37500 points

    Hello

    The USBVBUS drive is a 5v circuit.

    a) The monitoring reference says 5v in the USB3 User Guide, " www.ti.com/.../spruhj7a.pdf "

    b)  the Power Distribution Switch for OTG applications could have 3.3v in.    

    c) the Load Switch is replaced with a Voltage comparator, if your 3.3v input is > 3.3v USBVREf, the output of the comparator would be 5v.

    Regards,

    Joe Quintal

  • 0 in reply to Radio-Joe
    Prodigy 70 points
    Hi,

    We don't have 5V supply on board. Only 12V and 3.3V are available.

    Kindly elaborate on point C in the above mail.

    Also, please explain how the signals USBVBUS and USBDRVVBUS are related.

    Thanks,
    Remya
  • 0 in reply to Remya Nellikkal
    TI__Mastermind 37500 points
    a) point C - the spruhj7a.pdf Keystone 2 USB3 user guide, Table 2-6 lists USBVBUS as a 5v input monitor of VBUS, and for OTGADP it is a 5v output. In your case if VBUS is 3.3v, using a voltage comparator with your value (example 3v), an analog voltage comparator that is open collector drive, (only pulls to GND) would have a pullup resistor to 5v. www.ti.com/.../tlv3011.pdf

    You would need a small boost converter 3.3 to 5v. TPS61099

    b) USBDRVVBUS - this is a 1.8v signal that is supposed to protect the 5v input from being powered until the 3.3v K2K power supply is OK.

    if you had a dual voltage comparator - you would have the internal 3.3v power supply > setpoint, and the external 3.3v VBUS > setpoint,
    to drive the USBVBUS to 5v.

    please look at the Advantech TCI6638K2K(TCII6636K2H) EVM for the reference design. "www2.advantech.com/.../EVMK2HX.aspx"

    Regards,
    Joe Quintal