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TUSB9261 question

Thomas Chin
Prodigy 20 points
Other Parts Discussed in Thread: TUSB9260

1) Datasheet state a 1.8 external clock oscillator is required but the device only has power input of 3.3v and 1.1v. can I use a 3.3v oscillator instead. The Implementation guide  (SLLA315C) page 10 shows a VDD33 but the datasheet page 17, specify a 1.8v clock source. Can this be a carry over from the older part TUSB9260?

2) If the device is Self power as oppose to USB cable power, then what is the purpose of the input pin 50 (USB_VBUS)?

The User Guide (SLLU139) page 14 already has a GPIO4 called SELF_PWR which I'm not sure if the FW is using this to determine where the power is being supply. If GPIO4 is used this way then what does pin 50 do?

3) The USB_VBUS, pin 50 input implementation guide specify a 90.9K and 10K, this provide a 0.5v input. I would prefer to use standard resistor value in our inventory. What is the voltage range requirement for this input pin?

  • 0
    TI__Mastermind 36085 points

    Hello Thomas

    1)  Officially You must use an 1.8V oscillator, some customer's applications uses a 3.3V oscillator but they have to implement a voltage divider from 3.3V to 1.8V between the oscillator and the XI terminal. However TI does not guarantee a good operation of the device with this kind of configuration.

    2 and 3) The SELF_PWR pin is used by the default firmware as a source voltage selector, meanwhile the USB_VBUS pin is a USB bus power monitor which should has a voltage divider with a maximum rate of 0.2, this value comes from the rate between the USB bus voltage and the maximum input voltage on USB_VBUS (5V and 1.15V respectively).,

    P.S: The image on the implementation guide (page 10) is referring an oscilator suplied by 3.3V, which does not means its output is at the same voltage.

    Regards,

    Diego.

  • 0 in reply to Diego Cortes
    Prodigy 20 points

    1) OK, the voltage range for pin 50 can be 0.5 to 1V (max rate of 0.2 x VBUS = 0.2 x 5v = 1v ?).

    I assumed, the rate you are referring to is the percentage of the VBUS

    Therefore any resistor network divider value that provide this range would be valid.

    To confirm, I'm using 10K and 78K, this effectively provide a 0.58v to pin 50, I believed this is acceptable?

    2) Secondly, the USB_VBUS (pin50) inform the device that there is a USB connection? ...and the "SELF_PWR" signal which is GPIO4 informs the device where power is coming from?

    Thanks,

  • 0 in reply to Thomas Chin
    TI__Mastermind 36085 points

    Hello Thomas,

    1) Yes, Your assumption is correct and your resistance values looks fine because provides an acceptable voltage level and quite similar power consumption in compare with the reference design. However,  We have no testing records for this resistance values and We can not guarantee a free issues design for this configuration.

    2) You are correct, the USB_VBUS (pin 50) acts as a USB connection monitor meanwhile the SELF_PWR (GPIO4) configures the origin of source power.

    Best Regards,

    Diego.