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ISO6721-Q1: Use ISO6721 to replace ISO7221, what need to be taken care of if compatible with TTL input?

Zoe Yang
Intellectual 2210 points
Part Number: ISO6721-Q1
Other Parts Discussed in Thread: ISO6721, ISO6741

Hi team, 

As we know,ISO7221 is TTL input type and ISO6721 is CMOS input type. Do you have any suggestion on the compatible design on these two device?  

ISO6721 input voltage:

ISO7221 input voltage:

Customer circuit is shown below:

Do you have any suggestion on the threshold of INPUT/OUTPUT signal

  • 0
    TI__Genius 9185 points

    Hi Zoe, 

    Thank you for your question.

    The ISO6721 device is a pin-to-pin compatible device ISO7221.

    I believe there should be no difference in the circuit design in regards to the high level and low level voltage levels. I will confirm this with my team and get back to you on this.

    Can you please share the exact part number for the ISO7221 that the customer currently has? This would be helpful since there are multiple variants of the ISO7221.

    Regards,
    Aaditya Vittal

  • 0 in reply to Aaditya Vittal
    TI__Intellectual 2210 points

    The full part number is ISO7221AQDRQ1. Please feedback to me if you had conclusion. 

  • 0 in reply to Zoe Yang
    TI__Genius 9185 points

    Hello,

    Thank you for sharing the part number. I will discuss with the team and provide you with some feedback.

    Regards,
    Aaditya Vittal

  • 0 in reply to Aaditya Vittal
    TI__Genius 9185 points

    Hello,

    Thank you for your patience. 

    I was able to discuss the information with my team in regards to your questions. I have answered them before:

    Zoe Yang said:
    Do you have any suggestion on the compatible design on these two device?

    As I mentioned previously the ISO6721 is pin-to-pin compatible with the ISO7221. 

    Zoe Yang said:
    Do you have any suggestion on the threshold of INPUT/OUTPUT signal

    As far as the input/output voltage thresholds go, it really depends on the other devices that are attached on either side of the isolator, such as the MCU. If the MCU has an output that is CMOS output, the ISO6741 should be easier to setup in comparison to the ISO7221. We recommend to check the other devices and determine the type of signals coming in and out of the digital isolator.

    Regards,
    Aaditya Vittal