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LMP8480: Vsense calculation

Johnson Cheah
Intellectual 1300 points
Part Number: LMP8480

Hi Team,

If VCC is 5V, how to calculate the Vsense?

Does it Vsense = 5V / Av ? 

Besides, if VCC below 16V, the internal 14V LDO will not work. Am I right?

regards,

Johnson

  • 0
    TI__Mastermind 25085 points
    Hello Johnson,

    Thanks for using our forum. It is a holiday for TI employees in the United States today. Our next business day is on Monday (11/26), starting at 8 a.m. mountain standard time. We will get back to you with a response to your issue on that day.
  • 0 in reply to Patrick Simmons
    TI__Mastermind 25085 points
    Hello Johnson,

    Vsense at the max load or the max current value you want to measure is (5V-0.25V)/Gain. From that you can calculate the needed Rshunt and Vsense will then be Rshunt * ILoad. Yes at a VCC below 14V, the LDO will not be used.
  • 0 in reply to Patrick Simmons
    TI__Intellectual 1300 points

    Hi Patrick,

    what is the 0.25V? Why VCC need to minus 0.25V? 

    Besides, what is VOMAX? It has 0.5V max for VOMAX, how to interpret it?

     

  • 0 in reply to Johnson Cheah
    TI__Mastermind 25085 points

    Hello Johnson,

    I was referencing the following section, which is related to the VOMAX specification you saw.

    VOMAX in the above paragraph was assumed to be 250mV.  At worst it will to be 0.5V.  VOMAX is the difference between the supply and the device maximum output.  If you want a good understanding of why this exists, I think these precision lab videos are a good source: link1, link2, link 3.  Although these linked videos pertain to the amplifier groups products, the information is still relevant to current sensors.