INA231AIYFDR datasheet(16/44 Pages) TI1

16 / 44 page

Current

BusVoltage

20,000

Power =

INA231

SBOS644B – FEBRUARY 2013 – REVISED AUGUST 2017

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Product Folder Links: INA231

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Programming (continued)

(1)

Conditions: Load = 10 A, VCM = 12 V, RSHUNT = 2 mΩ, and VBUS =11.98 V.

The LSB for the Bus Voltage register (02h) is a fixed 1.25 mV/bit. This fixed value means that the 11.98 V

present at the BUS pin results in a register value of 2570h, or a decimal equivalent of 9584. Note that the MSB of

the Bus Voltage register is always zero because the BUS pin is only able to measure positive voltages.

The Power register (03h) is then calculated by multiplying the decimal value of the Current register, 10000, by

the decimal value of the Bus Voltage register, 9584, and then dividing by 20,000, as defined in Equation 4. For

this example, the result for the Power register is 12B8h, or a decimal equivalent of 4792. Multiplying this result by

the power LSB (25 times the [1 × 10–3 Current_LSB]) results in a power calculation of (4792 × 25 mW/bit), or

119.8 W. The Power register LSB has a fixed ratio to the Current register LSB of 25 W/bit to 1 A/bit. For this

example, a programmed Current register LSB of 1 mA/bit results in a Power register LSB of 25 mW/bit. This ratio

is internally programmed to make sure that the scaling of the power calculation is within an acceptable range. A

manual calculation for the power being delivered to the load would use a bus voltage of 11.98 V (12VCM – 20 mV

shunt drop) multiplied by the load current of 10 A to give a result of 119.8 W.

(4)

Table 1 shows the steps for configuring, measuring, and calculating the values for current and power for this

device.

Table 1. Configure, Measure. and Calculate Example(1)

STEP #

ADDRESS

CONTENTS

DEC

LSB

VALUE

Step 1

Configuration

00h

4127h

—

Step 2

Shunt

01h

1F40h

8000

2.5 µV

20m V

Step 3

Bus

02h

2570h

9584

1.25 mV

11.98 V

Step 4

Calibration

05h

A00h

2560

—

Step 5

Current

04h

2710h

10000

1 mA

10 A

Step 6

Power

03h

12B8h

4792

25 mW

119.8 W

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