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ISO1540: It is a question about TI's I2C driver ISO 1540 specification.

Ozawa
Intellectual 850 points
Part Number: ISO1540

I have a question.

Does this device impair the I 2 C bus during Power Down?

Question detail===============

DataSheet "Section 6.1 Absolute Maximum Ratings"

SDA 1, SCL 1 MAX VCC 1 + 0.5
SDA 2, SCL 2 MAX VCC 1 + 0.5

This is described.
Looking at this content, Absolute Maximum Rating = 0.5 V at Power Down.

In that case, if a high signal is input to the terminal, it leaks from the protection diode and disturbs the I 2 C bus

on the other hand
DataSheet "8.5 Device Functional Modes"

VCC1 or VCC2 <2.1 V

In this case, OUTPUT becomes High Impedance or Float regardless of the value on the input side.

In this case, it does not seem to disturb the I2C bus even during power down.

Which is right?
  • 0
    TI__Intellectual 2325 points
    Hi Ozawa,

    Thanks for using E2E.

    The output will become high-Z and float as described in section 8.5.

    To clarify more on Section 6.1 (Absolute Maximum ratings), this is _not_ an operational rating but rather a stress/damage limit rating of the device. So, in this particular case, when Vcc1 = 0, then the table should be read as :" if vcc1 = 0, then the voltage applied on the SDA1/2, SCL 1/2 pins should be less than 0.5V ,otherwise damage will occur". This is documented in footnotes 1, 2 and 3 in section 6.1

    Best regards,
    Abhi