INA3221: INA3221 voltage readings.

Dinesha Karunathilake

Prodigy 20 points

Part Number: INA3221

How to find the unit (milli volts ?) of the register reading we get?

It is obvious that the bus voltage is given in milli volts. What about the shunt voltage?

Thank you

over 6 years ago

0 Peter Iliya over 6 years ago

TI__Mastermind 26640 points

Hello Dinesha,

Could you send us the register reading you see and what you expect? Are you using the INA3221EVM?

Regards,
Peter Iliya
Current Sense Applications

0 Dinesha Karunathilake over 6 years ago in reply to Peter Iliya

Prodigy 20 points

I am using Switchdoc labs breakout board with INA3221 chip. I want to get a millivolts value. This shunt voltage value is very small, therefore we cannot measure it with a multimeter and compare.

0 Jason Bridgmon over 6 years ago in reply to Dinesha Karunathilake

TI__Genius 14825 points

Dinesha,
The native 1-LSB step size of the ADC on the INA3221 is 40uV for the shunt voltage, and 8mV for the bus voltage. So, if for example, you read x0003h from the shunt voltage register, that would mean the voltage measured is 3 x 40uV = 120uV. Similarly, if the bus voltage register read x0005h then the bus voltage would be 5 x 8mV =40mV.
Note, the registers are left shifted 3 bits, so in the example above, you would actually read x0018h, then right shift 3 bits to get x0003h.

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INA3221: INA3221 voltage readings.