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ISOW7844: Input voltage condition of ISOW7844DWE

MESH
Intellectual 830 points
Part Number: ISOW7844

Hello,

I am designing circuit that is used ISOW7844DWE.
Voltage clamp circuit is connected ISOW7844DWE input (INx) to clamp to voltage of 5V from 30V external input voltage.
This voltage clamp circuit consists 100kohm current limit resistor and two clamp diodes (one of the diode is connected to VISO and another one is connected to GND2).
Output voltage of this voltage clamp circuit is approximate VISO + 0.6V.


Absolute maximum rating of ISOW7844DWE input voltage is "VISO + 0.5V (3)" on the datasheet.
Contents of the note(3) is "This value depends on whether the pin is located on the VCC or VISO side. The maximum voltage at the I/O pins should not exceed 6V"
I would like to check if there is a problem with the ISOW7844DWE for input voltage of VISO + 0.6V.

Regards,
MESH

  • +1
    TI__Genius 17100 points

    Hi MESH,

    Thank you for posting to E2E! Input voltages above VISO are not recommended because the input pin's protective structure shown below may become forward biased and be damaged since it is not designed to sink high or continuous currents:



    VISO + 0.6V is not very high above the VISO + 0.5V maximum rating, especially with a limited input current like in this case, so it's possible no immediate damage occurs in the device. However, since this is even marginally outside of the absolute maximum ratings, we cannot guarantee device reliability or performance over its lifetime if operated this way.

    Please let us know if you have any additional questions.


    Thank you,
    Manuel Chavez

  • 0 in reply to Manuel Chavez
    Intellectual 830 points

    Hello, Manuel

    Thank you for your reply.

    Your reply is very helpful for me.

    I will use a zener diode instead of two switching diodes to comply with rating voltage.

    Regards,

    MESH