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BQ76925

IBRAHIM NAZIR
Prodigy 10 points

hi

I am making a circuit for battery management. but I have some problems with its VIOUT for sensing the current every time i got reading with 16 times higher current then actual that is flowing through it..... i am using 0.001 Ohm resistance as current sense.... I am using these formulas for Isense

VSENSE = -(VIOUT(SENSEP) -VIOUT(SENSEN))/ GVIOUT
ISENSE= -VSENSE/ RSENSE
as described in datasheet on page 16.
but something is still missing that i can't taking it into my knowledge...

kindly please help me... 

 

  • 0
    TI__Guru 54715 points

    Sorry for the late reply, hopefully you have successfully found the cause and corrected the problem.

    A consistent error of 16x is not obvious.  A gain selection error would produce a factor of 2, (4 vs 8) and a reference error may shift the range by 2x, although it shifts the reference point also. Good things to check might include: Verify are that the register settings are the same between measurement of SENSEP and SENSEN.  Only the I_AMP_CAL bit should be changed between measurements. Be sure the loading on VIOUT is the same between the measurements.  Be sure to allow sufficient settling time after turning on the output or switching I_AMP_CAL before taking the reading.  You can observe the transition time in your circuit, but remember to leave the probe for both measurements, and that the probe will load the circuit changing the value.  Also check the calculations to be sure they produce the result expected.