INA229 datasheet(31/48 Pages) TI

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The RSHUNT term is the resistance value of the external shunt used to develop the differential voltage across the

IN+ and IN– pins. Use Equation 2 for ADCRANGE = 0. For ADCRANGE = 1, the value of SHUNT_CAL must be

multiplied by 4.

SHUNT_CAL = 13107.2 x 10

6 x CURRENT_LSB x R

SHUNT

(2)

where

• 13107.2 x 106 is an internal fixed value used to ensure scaling is maintained properly.

• the value of SHUNT_CAL must be multiplied by 4 for ADCRANGE = 1.

CURRENT_LSB =

Maximum Expected Current

(3)

Note that the current is calculated following a shunt voltage measurement based on the value set in the

SHUNT_CAL register. If the value loaded into the SHUNT_CAL register is zero, the current value reported

through the CURRENT register is also zero.

After programming the SHUNT_CAL register with the calculated value, the measured current in Amperes can be

read from the CURRENT register. The final value is scaled by CURRENT_LSB and calculated in Equation 4:

Current [A] = CURRENT_LSB x CURRENT

(4)

where

• CURRENT is the value read from the CURRENT register

The power value can be read from the POWER register as a 24-bit value and converted to Watts by using

Equation 5:

Power [W] = 3.2 x CURRENT_LSB x POWER

(5)

where

• POWER is the value read from the POWER register.

• CURRENT_LSB is the lsb size of the current calculation as defined by Equation 3.

The energy value can be read from the ENERGY register as a 40-bit unsigned value in Joules units. The energy

value in Joules is converted by using Equation 6:

Energy [J] = 16 x 3.2 x CURRENT_LSB x ENERGY

(6)

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INA229-Q1

SLYS024A – MAY 2020 – REVISED JUNE 2021

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INA229 датащи(PDF) 31 Page - Texas Instruments