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INA3221: Load Vs. Supply Connection....

Jeremy Labbe
Prodigy 10 points

Part Number: INA3221

I have an application where I am measuring voltage and current in a pass through device. The device can sit between two others devices in various configurations where all the devices have INA3221 voltage and current monitors. Because of the varied configuration, there are times when the load and supply side of a monitoring channel are reversed. We are having some issues with the INA that do not track with configuration, but I keep coming back to notation in the datasheet that specifies a defined supply and load connection point.....

 If a configuration violates this, having the supply connection on IN- and the load side on IN+ what are the reprocutions? 

Two INAs in the same current path on opposite sides of connectors are reading values that have a fairly significant offset to one another. In some circumstances this offset has a coponent that scales with load. We are validating with external measurements and we keep getting a channel on a device reading an incorrect current. 

Please let me know your thoughts and I can fill in details as necessary. 

-J

  • 0
    TI__Mastermind 26335 points

    Hello Jeremy,

    Thanks for considering to use Texas Instruments.  I unfortunately cannot see the image you were trying to upload.  However, I suspect your issue has something to do with the chart below.  Do you have an input filter between your shunt and the VIN+ and VIN- pins?  If you do, whatever resistance you chose will increase the sense voltage perceived by the device.  Do you have kelvin connections coming off of your shunt?  If you don't you may be adding so series resistance to your sense resistor.  You should be able to have the bus on either the VIN+ side or VIN- side.  Depending on direction of current, the actual BUS value and the measured BUS will be different.  In the instance the bus is on the VIN+ side, the actual bus value would be roughly the measured Vsense + the the measured bus.