INA3221 datasheet(28/50 Pages) TI2

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7.6.2.2 Channel-1 Shunt-Voltage Register (address = 01h), [reset = 00h]

This register contains the averaged shunt-voltage measurement for channel 1. This register stores the current

shunt-voltage reading, VSHUNT, for channel 1. 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 MSB = 1.

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

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

1. Take the absolute value: 80mV

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

3. Convert this number to binary = 011 1110 1000 0_ _ _ (last three bits are set to 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

Table 7-7. Channel-1 Shunt-Voltage Register

SIGN

SD11

SD10

SD9

SD8

SD7

SD6

SD5

SD4

SD3

SD2

SD1

SD0

—

R-0

LEGEND: R/W = Read/Write; R = Read only; -n = value after reset

Table 7-8. Channel-1 Shunt-Voltage Register Field Descriptions

Bit

Field

Type

Reset

Description

SIGN

Sign bit.

0 = positive number

1 = negative number in twos complement format

14-3

SD11-0

Channel-1 shunt-voltage data bits

2-0

Reserved

7.6.2.3 Channel-1 Bus-Voltage Register (address = 02h) [reset = 00h]

This register stores the bus voltage reading, VBUS, for channel 1. Full-scale range = 32.76V (decimal = 7FF8);

LSB (BD0) = 8mV. Although the input range is 26V, the full-scale range of the ADC scaling is 32.76V. Do not

apply more than 26V.

Table 7-9. Channel-1 Bus-Voltage Register

SIGN

BD11

BD10

BD9

BD8

BD7

BD6

BD5

BD4

BD3

BD2

BD1

BD0

—

R-0

LEGEND: R/W = Read/Write; R = Read only; -n = value after reset

Table 7-10. Channel-1 Bus-Voltage Register Field Descriptions

Bit

Field

Type

Reset

Description

SIGN

Sign bit.

0 = positive number

1 = negative number in twos complement format.

14-3

BD11-0

Channel-1 bus-voltage data bits

2-0

Reserved

INA3221

SBOS576C – MAY 2012 – REVISED SEPTEMBER 2025

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