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

over 6 years ago

0 Patrick Simmons over 6 years ago

TI__Mastermind 24295 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 Patrick Simmons over 6 years ago in reply to Patrick Simmons

TI__Mastermind 24295 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 Johnson Cheah over 6 years ago 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 Patrick Simmons over 6 years ago in reply to Johnson Cheah

TI__Mastermind 24295 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.

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LMP8480: Vsense calculation