8 Application and Implementation

Note

Information in the following applications sections is not part of the TI component specification,

and TI does not warrant its accuracy or completeness. TI’s customers are responsible for

determining suitability of components for their purposes, as well as validating and testing their design

implementation to confirm system functionality.

8.1 Application Information

The INA232 is a current shunt monitor with an I2C- and SMBus-compatible interface. The device monitors

a shunt voltage drop to calculate the current and bus voltage at IN– pin to determine power. Programmable

calibration value, conversion times, and averaging (combined with an internal multiplier) enable direct readouts

of current in amperes and power in watts.

8.1.1 Device Measurement Range and Resolution

The INA232 device supports two input ranges for the shunt voltage measurement. The supported full scale

differential input across the IN+ and IN– pins can be either ±81.92 mV or ±20.48 mV depending on the

ADCRANGE bit in the Configuration Register (0h) register. The range for the bus voltage measurement at the

IN- pin is from 0 V to 52.42 V, but is limited by process ratings to the max operating voltage.

Table 8-1 provides a description of full scale voltage on shunt and bus voltage measurements, along with their

associated resolution.

Table 8-1. ADC Full Scale Values

PARAMETER

FULL SCALE VALUE

RESOLUTION

Shunt voltage

±81.92 mV (ADCRANGE = 0)

2.5 µV/LSB

±20.48 mV (ADCRANGE = 1)

625 nV/LSB

Bus voltage

0 V to 52.4 V (Limit usable range to recommended operating

voltage)

1.6 mV/LSB

The device shunt voltage and bus voltage measurements are read through the Shunt Voltage register (1h) and

Bus Voltage register (2h), respectively. The digital output in shunt voltage and bus voltage registers is 16 bits.

The shunt voltage measurement can be positive or negative due to bidirectional currents in the system; therefore

the data value in shunt voltage register can be positive or negative. The bus voltage register data value is always

positive. The output data can be directly converted into voltage by multiplying the digital value by its respective

resolution size.

Furthermore, the device provides the flexibility to report calculated current in Amperes, power in Watts, as

described in Current and Power Calculations.

8.1.2 Current and Power Calculations

For the INA232 to report current values in Amperes, a constant conversion value must be written in the

calibration register that is dependent on the selected CURRENT_LSB and the shunt resistance used in the

application. 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 it directly defines the maximum

resolution of the CURRENT register. While the smallest CURRENT_LSB value yields highest resolution, it is

common to select a higher round-number (no higher than 8x) value for the CURRENT_LSB to simplify the

conversion of the CURRENT.

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INA232

SBOSAA2 – DECEMBER 2022

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