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DS90UB925Q-Q1 Application Questions

Anthony Ward
Prodigy 110 points
Other Parts Discussed in Thread: DS90UB925Q-Q1, DS90UH925Q-Q1

I have a couple of questions about the application of DS90UB925Q-Q1. Thank you in advance for helping.

(1) Can I leave the MODE_SEL pin open if we are using I2C registers to select modes?

(2) IDx pin says you must have a pullup resistor. What value would you recommend?

(3) Is there an ability to select IDx from I2C for the 925? If so, can we leave the IDx pin open?

(4) could you explain the use of the INTB pin? what sort of situation would call for an interrupt?

Thanks again

  • 0
    TI__Genius 14015 points

    Hi Anthony,

    1) Technically you could, if you have a local microcontroller. If you are programming the 925 from the back channel (through the deserializer) then there would be a chance that the 925 comes up in the wrong mode, where there isn't a back channel available. In either case, we still recommend using at least a pull-down, to prevent unknown behavior. Leaving this pin floating would not meet our recommended circuit, so we couldn't be sure that performance would be stable.

    2) The recommended values for IDx resistor dividers are shown in table 5. The first address does not require a pull-up resistor. 

    3) You can overwrite the address by writing to register offset 0x00. However, you shouldn't let the IDx pin float, because you wouldn't know which device address was latched in, you'd have to guess or poll the bus to find which device ID's are out there. Also, same as with the MODE_SEL pin, we couldn't be sure that performance would be stable in this non-recommended case.

    4) INTB on this device is used for remote interrupts coming from the deserializer. For example, if there is a touch screen, the touch controller could send a signal through the INTB_IN pin on the deserializer, and the 925 INTB pin will trigger. This lets the processor know that there is a touch event to process, so it can go pull that data. On HDCP compliant devices (such as DS90UH925Q-Q1), the INTB pin has additional interrupt sources that help with the authentication process.

    Thanks,
    Jason

  • 0 in reply to Jason Blackman
    Prodigy 110 points
    Thank you Jason!
    One more question: should the RES pins be tied directly to ground, or should I include a pulldown resistor to ground?
  • 0 in reply to Jason Blackman
    Prodigy 110 points
    Also, when you say performance is not guarunteed to be stable if the pin is open, is there any reason that the MODE_SEL pin would override the register value?
  • 0 in reply to Anthony Ward
    TI__Genius 14015 points
    Hi Anthony,

    The RES pin should be tied directly to ground.

    What I meant about the MODE pin is that if it is left open, and the voltage floats to a value other than those recommended in the datasheet, then we can't be sure that the part will function correctly. In general, once the part is powered up and the mode is written in register, there is no way for the pin to override that value.

    Thanks,
    Jason
  • 0 in reply to Jason Blackman
    Prodigy 20 points
    Dear Jason,

    I'm using the DS90UB9225Q INTB Pin for a very sensitive application and I was searching for more information whether an interrupt can be triggered for any other reason than an external INTB_IN PIN. I have found your answer mentioning other interrupt sources for DS90UH925Q-Q1.

    Where I can find more information for this subject for DS90UB9225Q ?

    Thank you!