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ONET1131EC: Are the two 4.7K resistors for the 2-wire interface pulled up to VDD or VCC?

D.C.
Prodigy 210 points
Part Number: ONET1131EC


Dear TI Support,

According to the datasheet, the two 4.7K ohm resistors for the 2-wire interface (SDA and SCK) are pulled up to VCC. Several locations within the datasheet show this -- (1) Pin Functions table on page 4/50 (2) Typical application circuits in Figure 46/48/49. However, in Section 7.2, Functional Block Diagram, the "2-Wire Interface & Control Logic" block is powered by VDD. Please explain why the the two 4.7K resistors are pulled up to VCC when the two-wire interface is powered by VDD. Is it better to keep VDD(digital) and VCC(analog) domains separate? Any possibility the datasheet has typos?

Thanks.

  • 0
    TI__Guru* 93570 points

    Hi David,

    I think VDD and VCC have been used for SDA and SCK pull up because both are 2.5V rated supply. Recommendation is to use VDD since this is the digital supply block and rise/fall time of SDA and SCK will not affect analog supply. Also, please note these two pins are 3.3V tolerant. Some I2C interfaces provide this 3.3V supply and it may be more convenient to use this supply instead.

    Regards,, Nasser

  • 0 in reply to Nasser Mohammadi
    Prodigy 210 points

    Hi Nasser,

    Thanks for your quick response. I will use VDD pull-up for these two 2-Wire interface signals.

    Best Regards,

    David