INA226 Negative and Positive voltages with common grounds

Daniel Caplan

Other Parts Discussed in Thread: INA226

I've seen this thread https://e2e.ti.com/support/amplifiers/current-shunt-monitors/f/931/t/295168 but I'm still not confident on how to utilize two INA226 when the positive and negative rails share a common ground. I want to monitor +/-28V. Looking at the -48V Telecom example, it looks like the isolation would be removed byt the fact that the microcontroller ground, positive rail ground, and negative rail ground are all the same.

over 8 years ago

0 Rabab Itarsiwala over 8 years ago

TI__Expert 4595 points

Hi Daniel,

We have a TI design for -48 V telecom example: TIDA-00313 - -48V Telecom Current/Voltage/Power Sense with Isolation. The INA226 ground is at -48 V in this example and the Isolator used does the translation. Please let me know if you have more questions on this design.

For the +28 V Bus INA226 can be used without the need for Isolation.

0 Daniel Caplan over 8 years ago in reply to Rabab Itarsiwala

Prodigy 60 points

Hi Rabab,
In that example, the GND_ISO and GND nets would be connected as it is one common ground in my setup. Doesn't this remove the isolation? Would I need to keep the microcontroller isolated from both INA226s?

Thanks,
Dan

0 Rabab Itarsiwala over 8 years ago in reply to Daniel Caplan

TI__Expert 4595 points

Hi Daniel,
The isolator is needed because GND_INA is at -48 V and the GND is at 0 V in this example. You will need the isolator in case of the -ve bus supply monitoring but will not need that for the positive case since the device is rated for upto +36 V common mode.

0 Daniel Caplan over 8 years ago in reply to Rabab Itarsiwala

Prodigy 60 points

Thanks for the confirmation Rebab. So does this schematic look correct to you then? The _OBOX_OUT power signals each connect to once side of a load, while the other side of each load connects to GND.

0 Rabab Itarsiwala over 8 years ago in reply to Daniel Caplan

TI__Expert 4595 points

Hi Daniel,

This looks right. R23 needs to be sized according to the Zener current and the other system currents that flow through it.

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INA226 Negative and Positive voltages with common grounds