INA231 datasheet(21/32 Pages) TI

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INA231

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SBOS644 – FEBRUARY 2013

DATA OUTPUT REGISTERS

Shunt Voltage Register (01h, Read-Only)

The Shunt Voltage register stores the current shunt voltage reading, VSHUNT. Negative numbers are represented

in twos complement format. Generate the twos complement of a negative number by complementing the

absolute value binary number and adding 1. Extend the sign, denoting a negative number by setting the MSB =

'1'.

Example: For a value of VSHUNT = –80 mV:

1. Take the absolute value: 80mV

2. Translate this number to a whole decimal number (80 mV ÷ 2.5 µV) = 32000

3. Convert this number to binary = 111 1101 0000 0000

4. Complement the binary result = 000 0010 1111 1111

5. Add '1' to the complement to create the twos complement result = 000 0011 0000 0000

6. Extend the sign and create the 16-bit word: 1000 0011 0000 0000 = 8300h

This register displays the averaged value if averaging is enabled. Full-scale range = 81.9175 mV (decimal =

7FFF); LSB: 2.5

μV.

BIT #

D15

D14

D13

D12

D11

D10

BIT

SIGN

SD14

SD13

SD12

SD11

SD10

SD9

SD8

SD7

SD6

SD5

SD4

SD3

SD2

SD1

SD0

NAME

POR

VALUE

Bus Voltage Register (02h, Read-Only)(1)

The Bus Voltage register stores the most recent bus voltage reading, VBUS.

This register displays the averaged value if averaging is enabled. Full-scale range = 40.95875 V (decimal =

7FFF); LSB = 1.25 mV. Do not apply more than 28 V on the BUS pin.

BIT #

D15

D14

D13

D12

D11

D10

BIT

—

BD14

BD13

BD12

BD11

BD10

BD9

BD8

BD7

BD6

BD5

BD4

BD3

BD2

BD1

BD0

NAME

POR

VALUE

(1)

D15 is always zero because bus voltage can only be positive.

Power Register (03h, Read-Only)

This register displays the averaged value if averaging is enabled.

BIT #

D15

D14

D13

D12

D11

D10

BIT

PD15

PD14

PD13

PD12

PD11

PD10

PD9

PD8

PD7

PD6

PD5

PD4

PD3

PD2

PD1

PD0

NAME

POR

VALUE

The Power register LSB is internally programmed to equal 25 times the programmed value of the Current_LSB.

The Power register records power in watts by multiplying the decimal values of the current register with the

decimal value of the bus voltage register according to Equation 4.

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