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ISO7041DBQEVM: Power supply for uart isolation

PENG XU
Prodigy 25 points
Part Number: ISO7041DBQEVM
Other Parts Discussed in Thread: ISO7742, , ISO7041

Tool/software:

Hi Team

We want to reduce the power consumption of our application and plan to switch from ISO7742 to ISO7401 for uart isolation (3.3V)

ISO7041DBQEVM was purchased and connected to 2 uart ports and worked properly. However, when I disconnected the power supplies to the ISO7401, the communication btw 2 uart kept going through the ISO7041DBQEVM as if the power supplies were still on.

Checked with the scope and the waveforms are clear and sharp on both ends for both RX and TX. 

I am assuming the ISO7041 is somehow powered up through the pullups on RX and TX of both ends but don't know if it's true. Please share some insight with me on this phenomenon because it's so attractive to me to use ISO7401 without power supplies under specific scenarios (such as: pull up resistors exist and connect to a power supply on both ends for UART communications only to reduce more power consumption.

A second question is: if that works, does it work with a 5V uart on one side and 3.3V on the other?

Thanks

Best

Philip Xu

  • 0
    TI__Genius 17385 points

    Hi Phillip,

    As you already know, the recommended operating conditions for the device supply voltage is between 1.71-5.5V for both sides.

    The absolute maximum ratings for the device supply voltage is up to 6V while the input voltage maximum is VCC+0.5V, as shown below:

    When the device is off, but input signal is applied, this violates the absolute maximum ratings. Violating the absolute maximum ratings can stress the device and cause reliability issues and damage to the device as well. 

    The reason why the device may be working is due to the input signal supplying enough current to drive the supply of the device. However, this causes significant stress to the device and can cause damage over time. We do not guarantee the operation of the device when absolute maximum ratings are violated.

    Regards,
    Aaditya V

  • 0 in reply to Aaditya V.
    Prodigy 25 points

    Thank you Aaditya.