INA3221

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SBOS576 – MAY 2012

Channel 1 Shunt Voltage Register (Address = 01h, Read-Only)

Full-scale range = 163.8 mV (decimal = 7FF8); LSB (SD0): 40

μV. This register contains the averaged shunt

voltage measurement for channel 1.

BIT

D15

D14

D13

D12

D11

D10

D9

D8

D7

D6

D5

D4

D3

D2

D1

D0

NAME

SIGN

SD11

SD10

SD9

SD8

SD7

SD6

SD5

SD4

SD3

SD2

SD1

SD0

—

—

—

POR

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

VALUE

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 MSB = 1.

1. Take the absolute value: 80 mV

2. Translate this number to a whole decimal number (80 mV / 40 µV) = 2000

3. Convert this number to binary = 011 1110 1000 0--- (non-used bits are '0')

4. Complement the binary result = 100 0001 0111 1111

5. Add '1' to the complement to create the twos complement result = 100 0001 1000 0000

6. Extend the sign and create the 16-bit word: 1100 0001 1000 0000 = C180h

BIT

D15

D14

D13

D12

D11

D10

D9

D8

D7

D6

D5

D4

D3

D2

D1

D0

NAME

SIGN

BD11

BD10

BD9

BD8

BD7

BD6

BD5

BD4

BD3

BD2

BD1

BD0

—

—

—

POR

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

VALUE

(1)

While the input range is 26 V, the full-scale range of the ADC scaling is 32.76 V. Do not apply more than 26 V.

Copyright © 2012, Texas Instruments Incorporated

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