# LTC2991 current measurement with voltage divider

Hi,

I am studying the following voltage divider circle in LTC2991 for current measurement. I have a question for the current measurement LSB value. Appreciate any advice.

As I understand, the voltage divider will divide differential voltage in 0.01 ohm. If LTC2991 Differential voltage is 19.075μV/LSB, the differential voltage LSB across 0.01 ohm (with voltage divder is 71.5K top resistor and 10.2k bot resistor) will be 8 x 19.075μV= 152.787μV/LSB.

In calculation, the circuit current measurement should be 152.787 / 0.01 = 15.27mA /LSB. However, the datasheet is 15.54mA/LSB. Slightly different.

Might I know if any problem in my Calculation? Appreciate if any advise.

Thank you.

Mark

• Greetings Mark,

Great question!  I believe that the discrepancy in values is due to not factoring in the sense resistor tolerance and TUE value.  Multiplying 15.27 by 1.01 (1% res) produces a result of 15.42.  Multiplying this by the 1.0075 (TUE) results in a value of ~15.54.

Thank you and best regards,