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Original question:

LM25066I: What is the accuracy of current sense when VIN-SENSE=1mV and 46mV?

LM25066I: What is the accuracy of current sense when VIN-SENSE=1mV and 46mV?

Chris Wu30
Prodigy 40 points
Part Number: LM25066I

Hi Praveen,

Please find the report as below that I used LM25066i to do the design. I found there an offset(around -0.518A) is always appeared.

What could be the cause of this symptom?

Now I need to define the spec of current accuracy for customer and how should I make the tolerance come out for light load(Vrs<5mV) & other load respectively? (Rs=1mΩ)

Thank you.

  • 0
    TI__Guru 57737 points
    Hi Chris,

    From your report it is evident that with increase in Current, the measurement accuracy increases and vice-versa. The reason is as mentioned in the datasheet is primarily due to offset voltage of internal amplifier and external noise. So, we recommend the current sense voltage not to be less than 5mV for accurate measurement. You are trying to measure currents (<1A) which will cause a voltage drop <1mV with a a 1m Ohm Sense resistor. This is bound to cause more error.
    As mentioned before, for better accuracy choose LM25066IA or use an external current sense amplifier with low offset voltage.

    Regards,
    Praveen