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Original question:

LM74910-Q1: LM74910-Q1 IMON accuracy questions

LM74910-Q1: Input referred offset and Vimon

Che Wen Yeh
Expert 1010 points
Part Number: LM74910-Q1


Tool/software:

Hi,

We have encountered a situation where, under no-load conditions, Vimon measures 0.2~0.5V. Is this caused by V(offset)?

And how to calculate max Vimon for V(offset)? Thanks.

  • 0
    TI__Guru 50705 points

    Hi Che Wen Yeh,

    This can be an expected behavior based on RSET and RIMON values.

    As an example, if the offset is around -500uV, the current through RSET (50ohms) will be 10uA and around 9uA will be flow to IMON pin.

    With RIMON of 15.4k, it will read 15.4k * 9uA = 138mV even at no load.

    Hence, max current that can flow into RIMON will be (0.9*offset_max/RSET) even at no load.

    Regards,

    Shiven Dhir

  • 0 in reply to Shiven Dhir
    Expert 1010 points

    Hi Shiven,

    So, if the maximum error is 2.1mV, Rset is 50 ohms, and Imon is 9k ohms, the maximum error would be 0.378V under no-load conditions? Additionally, our customer is currently sorting the Vimon voltage error under no-load conditions. Could you suggest a suitable voltage range for this? Thank you.

  • 0 in reply to Che Wen Yeh
    TI__Guru 50705 points

    Yes,

    VIMON can be 0.378V.

    I didnt understand the question. Can you re-frame it? What is the help needed from my side?

    Regards,

    Shiven Dhir

  • 0 in reply to Shiven Dhir
    Expert 1010 points

    During the SMT process, our customer measures the Vimon under no-load conditions during functional testing. 

    So, under the condition of Voffset, would you recommend setting the Vimon criteria to 0~0.378V to ensure the LM74910 is functioning properly? Thanks.

  • +1 in reply to Che Wen Yeh
    TI__Guru 50705 points

    Hi Che wen Yeh,

    With some margin, they can keep 0-400mV.

    Regards,

    Shiven Dhir