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ISO7741: Output Behavior

Expert 5300 points

Replies: 2

Views: 108

Part Number: ISO7741

We're evaluating the ISO7741F on the motor drive application. 

When VCC1(Pin 1) and EN1(Pin 7) are disconnected from the 5V bias power during safety concern with motor. And at the same time, the VCC2(pin 16) and (IND)Pin11 are still connected to 5V power(in normal operation). What is the behavior with the OUTD(PIN 6)? High Z, Low or high?



  • Hi Brian,

    Thank you for posting this question! Because Vcc1 and EN1 are unpowered, OUTD (pin 6) will be high impedance regardless of IND's state. This operation is acceptable for the device and will also not cause any damage.

    For relevant motor drive reference designs, feel free to visit the TI webpage below:

    Manuel Chavez

  • In reply to Manuel Chavez:

    Hi Brian,

    Hopefully all is well. My apologies, but I must clarify the scenario in your original post. According to our device's truth table (shown below), OUTD will remain a High Z if Vcc1 and EN1 are 0V or close to 0V. There is a transition region where the output side begins to power up between Vcc1 = 1.7V and 2.25V, so in this range output D is undetermined:

    If you'd like details regarding a specific power on or power off/disconnection waveform, please feel free to share it either through this forum or via PM. Otherwise, if Vcc1 and EN1 can be considered grounded when "disconnected," the output will be high impedance as stated above.

    Thank you,
    Manuel Chavez