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ISO7421E: DIGITAL ISOLATOR

navya diddi
Prodigy 40 points
Part Number: ISO7421E
Other Parts Discussed in Thread: ISO7721-Q1, ISO6721-Q1, , ISOW7841, ISOW7741, SN6505B, ISO7741-Q1, ISOW7741-Q1

Dear team,

I am looking for the digital isolator of automotive grade with 2.5kv ISOLATION and found this part ISO7421EQDWRQ1 parameters suits my application but i need to know  the output current varying with input current. 

Please help me out in getting this information asap.

Best Regards,

Navya.d

  • 0
    TI__Expert 5335 points

    Hello,

    Thank you for your question.

    I understand that you are looking for a digital isolator with 2.5kV isolation rating and automotive grade. The ISO7421EQDWRQ1 is an older device and we recommend you to use the ISO6721-Q1 or ISO7721-Q1 which is automotive grade and should work for your needs.

    Regards,
    Aaditya Vittal

  • 0 in reply to Aaditya Vittal
    Prodigy 40 points

    hello,

    thanks aaditya but i am looking for the graph as seen in image if possible please try to get it asap. 

  • 0 in reply to navya diddi
    TI__Mastermind 24485 points

    Hello Navya,

    There is no output dependence on input current for the device. 

    The input and output are powered independently and the output will operate according to the electrical characteristics listed in the datasheet.

    As you can see in the table below, there is no relationship between input and output current. The output will provide a mostly constant output impedance which can be calculated in the worst case based on the Max output voltage drop relative to the output current.

    For example for Vol max at Iol = 4mA there is a maximum output of 0.4V which would correspond to an output impedance of 100Ohms (while typical is 50 Ohms). 

    If you are operating at a different supply setup, you will need to look at the corresponding electrical characteristics table. (For example with both supplies at 3.3V, you will need to refer to table 6.8 in the datasheet. 

    I would also agree with Aaditya's suggestion above that you use the ISO7721QDWRQ1 instead as it is the latest generation option that can be used in place of ISO7421E. 

    Best,

    Michael

  • 0 in reply to navya diddi
    Prodigy 40 points

    Dear aaditya,

    thanks for th information,i need clarification on 2 points one is 

    ISO7741QDWQ1-part can the I/O pins can be used for SPI communication?
    output current capability of this ISO7741QDWQ1 IC i want to know.
    Please answer asap.
    Best regards,
    navya.d
  • 0 in reply to navya diddi
    Prodigy 40 points

    Dear aaditya,

    This is our existing schematic for reference.

      

  • 0 in reply to navya diddi
    TI__Expert 5335 points

    Hi Navya,

    Thank you for your question.

    Yes, the ISO7741QDWQ1 device can be used for SPI communication. For more information on isolating SPI signals, please take a look at this link: https://www.ti.com/lit/ml/sllt215a/sllt215a.pdf 

    The output current of the ISO7741QDWQ1 is presented in the datasheet under recommended operating conditions. The high-level output current capability is -4mA and the low-level output current capability is 4mA.

    Looking at the schematics, the equivalent TI part for the ADuM5401 is ISOW7841/ISOW7741. 

    Regards,
    Aaditya Vittal

  • 0 in reply to Aaditya Vittal
    Prodigy 40 points

    Dear aaditya,

    thanks for the information,on 3.3v the output current is 2mA, for the same ISO7741QDWQ1 IC is their any separate isolated power supply provided?

    Or else we have to can u recommend if their is any seperate part for separate isolated power supply. for reference check below image.

  • 0 in reply to navya diddi
    TI__Expert 5335 points

    Hi Navya,

    There are two main solutions for isolating power supplies:

    1. You can build an isolated power supply using a push-pull transformer driver, such as the SN6505B. Please refer to the datasheet to find information to design an isolated power supply using this device: https://www.ti.com/lit/ds/symlink/sn6505b.pdf
    2. Another solution is the digital isolator with integrated DC to DC converter, such as the ISOW7741-Q1. The ISOW7741-Q1 and the ISO7741-Q1 have similar data channels. Please refer to the datasheet of this device for more information: https://www.ti.com/lit/ds/symlink/isow7741-q1.pdf

    Since your application requires a digital isolator and isolated power solution, we recommend you to use the ISOW7741-Q1 that integrates both into a single device.

    Regards,
    Aaditya Vittal