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ISO7741: Power-on/off behavior ISO7741F

Sebastian Bartels
Prodigy 10 points
Part Number: ISO7741
Other Parts Discussed in Thread: ISO7740, ISO7742,

Hello,
we want to use the  ISO7741F (default Low type) digital isolator in our application.
Our requirement is that the output must not go high unintentionally when power supply switched on and off (during the supply voltage rises and falls).
In this case the datasheet says the output is "undetermined" (datasheet section 9.4 table 2).

Question:
How can we ensure that the output does not go high unintenionally when the supply voltage rises and falls?
Is a Pull-down resistor or something else a solution?

Futher Information:
Data rate < 1 Mbps
VCCI = 3,3 V
VCCO = 5 V

Referenced datasheet: ISO7740, ISO7741, ISO7742 (SLLSEP4G –MARCH 2016–REVISED FEBRUARY 2020)

  • +1
    TI__Mastermind 27410 points

    Hello,

    Thank you for your question and providing all the details related to your system. Yes, a pull-down resistor can be connected to the out pins to ensure that the outputs do not go high during the power transitions. One note, make sure that the chosen resistor value will still allow the isolator to source enough current to output high during operation. A value of 4.7kΩ is recommended.

    Regards,
    Darrah