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ISOW7821: why the Viso output of ISOW7821 is not right ?

du kaizhu
Prodigy 50 points
Part Number: ISOW7821

Hi: 

1.   I use ISOW7821 for 5V on the VCC and SEL pin is shorted VISO,  Why  the VISO output is not 5V  ?   I  measure that VISO output  is about 2.2V by multimeter,   and  it is about 260kHz, duty cycle  50%

square wave.

2.   I use same circuit on the other board,  but on the other board he VISO output is  5V.  

  • 0
    TI__Guru 53025 points

    Hi Du Kaizhu,

    Sorry to hear about the issue. Could you please share me the schematic and the output voltage waveform where you are seeing 2.2V?

    The issue can happen if the power supply recommendations from section 11 of ISOW7821 datasheet are not followed. Please do share the above requested information so that I can comment better. Thanks.

    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    TI__Guru 53025 points

    Hi Du Kaizhu,

    Please do share the above requested information so that I can help you with the issue better, thanks.

    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    Prodigy 50 points

    Hi:

    My design schematic is shown below diagram.

    1.   I buy a lot of ISOW7821 from mouser, some chip  are placed on the board , they can operate normally.  so I can make sure that schematic is right.

         But,  some chip are place on the same board,  they can not operate normally, Viso is about 2.2V or 0.5V,.  I do not know why ?

    2.  My  soldering temperature is about 300 degree,  max time 2s ,  I think soldering may be ok !  

    3.  In a word, on the same circuit on the same board, some ISOW7821 can operate normally,  some ISOW7821 do not, and do not know why !

  • 0 in reply to du kaizhu
    TI__Guru 53025 points

    Hi Du Kaizhu,

    Thank you for your response. I see I have some concern on the schematic, can I write you an email on the email ID that you have used to create your TI account? You will also be able to share more information about your application and share waveform as well. Let me know, thanks.

    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    Prodigy 50 points

    Hi:

        Thank you for your response.  You can send me email, it is dukaizhu@maxsense.ai

  • 0 in reply to du kaizhu
    TI__Guru 53025 points

    Hi Du Kaizhu,

    Thank you for allowing me to reach out to you over email. Since we are continuing our discussion over email, I will go ahead and close this E2E post. Thanks.

    Regards,
    Koteshwar Rao