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DS90UB928Q-Q1: OEN and OSS_SEL control

Niko Tarnanen
Prodigy 30 points
Part Number: DS90UB928Q-Q1
Other Parts Discussed in Thread: ALP

What’s the recommended way to control OEN & OSS_SEL, when I want to enable GPIO and LVDS pins of the DS90UB928?

DS90UB928 datasheet states on chapter 9.4:

“OEN should be enabled LVDS outputs after PDB turns to high state and the internal circuit is stabled.”

Should I connect the OEN & OSS_SEL pins like this, if I want to enable outputs permanently?

Isn’t it possible to activate the UB928 outputs by writing the registers?

I left the OEN and OSS_SEL pins of the DS90UB928 floating. Then I set the OEN and OSS_SEL bits in the “General Configuration 0” register, but the outputs are not activated. This register writing doesn’t seem to do anything, although both registers are RW. I’m using the ALP software for the (remote) register writing. Am I missing something here?

  • 0
    TI__Guru** 107810 points

    Hello Niko,

    Niko Tarnanen said:
    What’s the recommended way to control OEN & OSS_SEL, when I want to enable GPIO and LVDS pins of the DS90UB928?

    Both, OEN and OSS_SEL should be high.

    Niko Tarnanen said:
    Should I connect the OEN & OSS_SEL pins like this, if I want to enable outputs permanently?

    Yes, this should be okay. Or you can pull these two pins directly to 1.8V with 10Kohm pull ups.

    Niko Tarnanen said:
    Isn’t it possible to activate the UB928 outputs by writing the registers?

    Yes, you can also control these two signals using the override function in register 0x02.

    Niko Tarnanen said:
    I left the OEN and OSS_SEL pins of the DS90UB928 floating. Then I set the OEN and OSS_SEL bits in the “General Configuration 0” register, but the outputs are not activated. This register writing doesn’t seem to do anything, although both registers are RW. I’m using the ALP software for the (remote) register writing. Am I missing something here?

    You need to make sure you enable bit [6] for overwriting function.

  • 0 in reply to Hamzeh Jaradat
    Prodigy 30 points

    Hello Hamzeh,

    Thank you very much, setting the bit 6 (OEN/OSS_SEL Override) did the trick, now I can control the outputs via registers. These register functions could be explained in more detail in the datasheet.

    Hamzeh Jaradat said:
    Yes, this should be okay. Or you can pull these two pins directly to 1.8V with 10Kohm pull ups.

    But doesn’t that violate the chapter 9.4 in the datasheet:

    “OEN should be enabled LVDS outputs after PDB turns to high state and the internal circuit is stabled.”

    That’s why I was wondering if I should connect the pull-up resistors to PDB. BTW, I don’t have 1.8V (VDDIO) on my board, it’s 3.3V single supply.

  • +1 in reply to Niko Tarnanen
    TI__Guru** 107810 points

    Yes, you are right! You should follow section 9.4

  • 0 in reply to Hamzeh Jaradat
    Prodigy 30 points

    Ok, thanks. Then I'll connect the pull-ups to PDB.