´

Power Register

Current Register

I C

2

Interface

Voltage Register

GND

V

BUS

ADC

V

I

A0

Alert

A1

SDA

SCL

C

0.1 F

BYPASS

m

10A

Load

Alert Register

V

(Supply Voltage)

S

+12V Supply

V

IN-

V

IN+

R

2m

SHUNT

W

ShuntVoltage

CalibrationRegister

2048

·

Current =

INA226

www.ti.com

SBOS547

– JUNE 2011

CONFIGURE/MEASURE/CALCULATE EXAMPLE

In this example, shown in Figure 23, a nominal 10A load creates a differential voltage of 20mV across a 2m

Ω

is connected to the VIN

measures less than 12V because the voltage at the VIN

– pin is 11.98V as a result of the voltage drop across the

shunt resistor.

Figure 23. Example Circuit Configuration

For this example, assuming a maximum expected current of 15A, the Current_LSB is calculated to be

457.7

μA/bit using Equation 2. Using a value for the Current_LSB of 500μA/Bit or 1mA/Bit would significantly

simplifiy the conversion from the Current Register and Power Register to amps and watts. For this example, a

value of 1mA/bit was chosen for the current LSB. Using this value for the Current_LSB does trade a small

amount of resolution for having a simpler conversion process on the user side. Using Equation 1 in this example

with a current LSB of 1mA/bit and a shunt resistor of 2m

Ω results in a Calibration Register value of 2560, or

A00h.

The Current Register (04h) is then calculated by multiplying the decimal value of the Shunt Voltage Register

contents by the decimal value of the Calibration Register and then dividing by 2048, as shown in Equation 3. For

this example, the Shunt Voltage Register contains a value of 8,000, which is multiplied by the Calibration

Register value of 2560 and then divided by 2048 to yield a decimal value for the Current Register of 10000, or

2710h. Multiplying this value by 1mA/bit results in the original 10A level stated in the example.

(3)

The LSB for the Bus Voltage Register (02h) is a fixed 1.25mV/bit, which means that the 11.98V present at the

Copyright

© 2011, Texas Instruments Incorporated

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