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ISO7741: Current consumption of one side when second side is unpowered.

TTL
Prodigy 20 points
Part Number: ISO7741

I have one question regarding current consumption of two Digital Isolators: ISO7741DBQR, ISO7742DBQR.
When Input-Side is unpowered and Output-Side is powered then Output-Side goes to default state (in this case HIGH state).
What is the current consumption on Output-Side in this situation?

Additional Information:

Supply voltage of Output-Side is 5V and Output-Side drivers are enabled (EN tied to 5V).
On Inputs of supplied side there can be voltages present coming from external ICs (e.g. SPI communication: 5V, 5MHz).

  • 0
    TI__Mastermind 49495 points

    Hi TTL,

    Welcome to TI E2E Forum and thank you for showing interested in ISO774x devices!

    The current consumptions of both VCC1 & VCC2 are given separately as ICC1 & ICC2 in the datasheet. You can refer to the section in datasheet where ISO7741 output is forced to default state (by applying an input same as default state) and read only ICC2 current. I am copying below this section for your quick reference.

    From the above table, I see that ICC2 is going to be 2mA typical and 3mA max for the case when output on VCC2 side is forced to default state by applying an input state that is same as default state. The ICC2 current will remain the same even if VCC1 is turned OFF as VCC1 & VCC2 dice are independently powered.

    The above data is valid for the case where the input on VCC2 side is also matched to default state or left floating. We do not have data for combinations of inputs where one channel is switching and others aren't.

    I hope that answers your question, thanks.

    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    Prodigy 20 points

    Hi Koteshwar,

    Thank you for the answer. In the top of the table you attached there is specified condition: Vcc1=Vcc2=5V. Situation with Vcc1=0V and Vcc2=5V is not described in data sheet.

    As I have no other data I will rely on your statement: "The ICC2 current will remain the same even if VCC1 is turned OFF". 

    Best regards, TTL.