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DAC70501: Interfacing IC2 with lower voltage than VDD

Lucas Neumann
Prodigy 90 points
Part Number: DAC70501

Hi,

i was wondering whether I can interface a DAC70501 using I2C when the I2C bus is at 3.3V (and pulled-up to 3.3V) while VDD of the DAC70501 is at 5V.

Obviously I want to save having to use level converters and according to the datasheet, everything from 1.62 is considered HIGH so I should be safe from this point of view.

However at the pin description text, the description of SDIN/SDA says that it has to be tied to supply voltage, which would be contraindicative in this case.

 

I guess the statement regarding having to pull the pin high has been made because this is how I2C works but I want to make sure this will work before I make the first test batch of PCBs.

VDD is going to be 5V so I can go up to that voltage on the DAC output, obviously. Only having 3.3V at the output wouldn't fit my needs.

Thanks!

  • +1
    TI__Guru 53193 points

    Hi Lucas,

    You can connect the SPI2C pin to the VDD pin voltage (5V) and then use 3.3V I2C without issue.  I recommend that SPI2C be connected to VDD rather than an external 3.3V voltage to prevent the the pin from being biased before the VDD node.

    Thanks,
    Paul

  • 0 in reply to Paul_Frost
    Prodigy 90 points

    Hi Paul,

    thanks for your reply. I understand that I should pull the SPI2C pin to VDD pin voltage (and I would have done that anyway). I was only talking about the I2C bus being operated at 3.3V (and pulled to 3.3V as that's the VDD and therefore maximum I/O voltage of the used microcontroller) and whether that would be ok or not but I think you answered that as well, when you said "use 3.3V I2C without issue"?

    Thanks and sorry for any misunderstandings, I'm not an english-native :-)
    Lucas

  • +1 in reply to Lucas Neumann
    TI__Mastermind 18826 points

    Hi Lucas,

    There is no issue in using 3.3V for I2C with VDD being 5V. You can pull up the SDA and SCL lines to 3.3V

    Regards.

    AK