INA231 datasheet(17/44 Pages) TI1

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Corrected_Full_Scale_Cal = trunc

Cal

MeasShuntCurrent

INA231_Current

INA231

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SBOS644A – FEBRUARY 2013 – REVISED JUNE 2017

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8.5.2 Programming the Power Measurement Engine

8.5.2.1 Calibration Register and Scaling

The Calibration register makes it possible to set the scaling of the Current and Power registers to the values that

are most useful for a given application. One strategy may be to set the Calibration register so that the largest

possible number is generated in the Current register or Power register at the expected full-scale point. This

approach yields the highest resolution based on the previously-calculated minimum Current_LSB in the equation

for the Calibration register (Equation 1). The Calibration register can also be selected to provide values in the

Current and Power registers that either provide direct decimal equivalents of the values being measured, or yield

a round LSB value for each corresponding register. After these choices have been made, the Calibration register

also offers possibilities for end-user, system-level calibration. By physically measuring the current with an

external ammeter, the exact current is known. The value of the Calibration register can then be adjusted based

on the measured current result of the INA231 to cancel the total system error, as shown in Equation 5.

(5)

8.5.3 Simple Current Shunt Monitor Usage (No Programming Necessary)

The INA231 does not require programming to read a shunt voltage drop and the bus voltage when using the

default power-on reset configuration and running continuous conversions of the shunt and bus voltage.

Without programming the INA231 Calibration register, the device is unable to provide either a valid current or

power value because these outputs are both derived using the values loaded into the Calibration register.

8.5.4 Default INA231 Settings

The default power-up states of the registers are shown in the Register Details section of this data sheet. These

registers are volatile, and if programmed to a value other than the default values shown in Table 3, they must be

reprogrammed at every device power-up. Detailed information on programming the Calibration register is given in

the Configure/Measure/Calculate Example section and calculated based on Equation 1.

INA231 Datasheet(PDF) 17 Page - Texas Instruments