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

8.1.1 Device Measurement Range and Resolution

The INA229 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 ±163.84 mV or ±40.96 mV depending on the

ADCRANGE bit in CONFIG register. The range for the bus voltage measurement is from 0 V to 85 V. The

internal die temperature sensor range extends from –256 °C to +256 °C but is limited by the package to –40 °C

to 125 °C.

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

their associated step size.

Table 8-1. ADC Full Scale Values

PARAMETER

FULL SCALE VALUE

RESOLUTION

Shunt voltage

±163.84 mV (ADCRANGE = 0)

312.5 nV/LSB

±40.96 mV (ADCRANGE = 1)

78.125 nV/LSB

Bus voltage

0 V to 85 V

195.3125 µV/LSB

Temperature

–40°C to +125°C

7.8125 m°C/LSB

The device shunt voltage measurements, bus voltage, and temperature measurements can be read through the

VSHUNT, VBUS, and DIETEMP registers, respectively. The digital output in VSHUNT and VBUS registers is 20-

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

therefore the data value in VSHUNT can be positive or negative. The VBUS data value is always positive. The

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

The digital output in the DIETEMP register is 16-bit and can be directly converted to °C by multiplying by the

above resolution size. This output value can also be positive or negative.

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

Coulombs and energy in Joules as described in Section 8.1.2.

8.1.2 Current , Power, Energy and Charge Calculations

For the INA229 device to report current values in Ampere units, a constant conversion value must be written in

the SHUNT_CAL register that is dependent on the maximum measured current and the shunt resistance used in

the application. The SHUNT_CAL register is calculated based on Equation 2. The term CURRENT_LSB is the

LSB step size for the CURRENT register where the current in Amperes is stored. The value of CURRENT_LSB

is based on the maximum expected current as shown in Equation 3, and it directly defines the 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 in order to simplify the conversion of the

CURRENT.

IN+ and IN– pins.

SHUNT_CAL = 13107.2 x 10

SHUNT

(2)

where

www.ti.com

INA229

SLYS023 – DECEMBER 2020

Copyright © 2020 Texas Instruments Incorporated

Submit Document Feedback

29

Product Folder Links: INA229