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ISO7762: ISO7762QDBQQ1 Default/Fault State

Part Number: ISO7762

Hello dear colleagues,

I hope you are doing well!
I am writing with regard to a technical question -on our ISO7762QDBQQ1- from our customer (Eaton).

Can someone tell me what the output state (HIGH/LOW) is like, if the supply voltage fails on the other side?

From the drawing, the customer interprets that if the TX IN supply is 0V, the RX OUT signal is HIGH. This would be important for the customer because one of the RX signals is a LOW active enable signal.
If, in the absence of a supply on the TX side, the RX signal and thus the enable were HIGH, the output side is in a safe state.

Thanks in advance,

  • Hi Candas,

    Thanks for reaching out.

    The default state of the output for a given device can be determined by the part number, i.e., ISO7762 (non-F) has a default state of HIGH and ISO7762F has a default state of LOW. Please check the below function table from ISO7762 datasheet that describes the expected state of output under all input test conditions.

    As you can see in the above table, the output goes to default state when the inputs are floating or when the input channel is unpowered. The default state of the output is indicated by the part number.
    It looks like customer is looking at an isolator with a default HIGH state, for this the right part number is the one that you have already chosen. The complete part number is ISO7762QDBQQ1. Thanks.

    Koteshwar Rao