INA226: Circuit Design for Isolated Voltage Measurement

Natesan Sambasivam

Prodigy 210 points

Part Number: INA226
Other Parts Discussed in Thread: INA260

Tool/software:

Hi,

We are planning to measure isolated voltage (Vbat) using the INA226 and need some assistance with the circuit design.

Which ground should be connected to the ground (pin no.7) of the INA226?
Is Vbus (pin 8) referenced to the INA226 ground (pin no. 7)? If so, would this result in a short between the two grounds in our system?

Note: We have two isolated power supplies: 5.0V (DGND) as VS and Vbat (PGND) as VBus. The 5.0V supply is used for the MCU, while Vbat is used for the power section.

Thank you.

Regards,
Sivam Natesan

over 1 year ago

0 Clemens Ladisch over 1 year ago

Guru 317250 points

All the other pins, including Vbus, are referenced to the GND pin. The INA226 cannot be used if you want to keep the grounds separated. For that, you would need an isolated ADC.

0 Mitch M over 1 year ago

TI__Mastermind 26345 points

Hey Sivam,

Clemens is correct that our device needs to be on the same ground as what it is measuring. An isolated ADC is one good option. Another option if you still want to use the INA226 would be to use a digital isolator, or mirror the current to a low side setup. Here are a few TIDA's that show how this can be done:

https://www.ti.com/tool/TIDA-00313 (digial isolator using INA226, but for negative voltages)

https://www.ti.com/tool/TIDA-01608 (digital isolator for high positive voltages, but with the INA260)

https://www.ti.com/tool/TIDA-00528 (current mirror to low side)

Regards,

Mitch

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INA226: Circuit Design for Isolated Voltage Measurement