For the INA4230 to report current values in Amperes, a constant conversion value must be written in each of the calibration registers that is dependent on the selected CURRENT_LSB and the shunt resistance used in the application for each channel. The value of the calibration register is calculated based on Equation 1. The term CURRENT_LSB is the chosen LSB step size for the CURRENT register where the current is stored. Equation 2 shows the minimum value of CURRENT_LSB is based on the maximum expected current, and the equation directly defines the maximum resolution of the CURRENT register. While the smallest CURRENT_LSB value yields highest resolution, this value is common for selecting a higher round-number (no higher than 8x) value for the CURRENT_LSB to simplify the conversion of the CURRENT.

The R_SHUNT term is the resistance value of the external shunt used to develop the differential voltage across the IN+ and IN– pins. Use Equation 1 for ADCRANGE = 0. For ADCRANGE = 1, the value of SHUNT_CAL must be divided by 4.

Equation 1.

where

• 0.00512 is an internal fixed value used to verify that scaling is maintained properly.
• CURRENT_LSB is a selected value for the current step size in amperes. Must be greater than or equal to CURRENT_LSB (minimum), but less than 8 x CURRENT_LSB(minimum) to reduce resolution loss.
• The value of SHUNT_CAL must be divided by 4 for ADCRANGE = 1.

Equation 2.

Note that the current is calculated following a shunt voltage measurement based on the value set in the SHUNT_CAL field. If the value loaded into the SHUNT_CAL field is zero, the current value reported through the CURRENT register is also zero.

After programming the SHUNT_CAL field with the calculated value, the measured current in Amperes can be read from the CURRENT register. Use Equation 3 to calculate the final value scaled by the CURRENT_LSB:

Equation 3.

where

• CURRENT is the value read from the CURRENT register

The power value can be read from the POWER register as an unsigned 16-bit value. Use Equation 4 to convert the power to Watts:

Equation 4.

where

• POWER is the value read from the POWER register.
• CURRENT_LSB is chosen lsb size for the selected channel.

The energy values can be read from the each ENERGY register as a 32-bit unsigned value. Use Equation 5 to convert the energy to Joules:

Equation 5.

where

• ENERGY is the value read from the each ENERGY register.
• CURRENT_LSB is chosen lsb size for the selected channel.