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INA293: Accuracy of INA193 amplifier for 1mA to 4A current range

Part Number: INA293
Other Parts Discussed in Thread: INA193, , INA228, INA229

Hi Team,

We are planning to use INA193 amplifier for 1mA to 4A current measurement. Customer wants to meet 1mA accuracy.

FSR=3V

Vsupply=3.3V

Vcommon mode voltage=40V

Rsense=25mohm.

With Rsense of 25mohm,we can't able to achieve the Vsn& Vsp conditions with single Gain.

We have chosen INA293A5-Q1 part, Gain =500 for measuring 0.5mA-240mA current range  and INA293A1-Q1 part, Gain =20 for measuring 240mA-4A current range.

Attached the schematics diagram and Error budget analysis herewith.

Request you to verify and confirm what is the maximum accuracy INA293A5-Q1 and INA293A1-Q1 parts can provide for the above conditions.

Request you to share the error calibration techniques also.

Regards,

D.Meenalochini

INA293_ACCURACY_ANALYSIS.xlsx

• Hello Meenalochini,

Please take a look at this error calculator link below.  I placed a screen shot for your convenience.  The error calculator uses VOS and the error but you could be limited by swing low as well as VOS for your low measurements.  Also you need to take into account the IB of 30µA on each input pin when you are attempting to measure 500µA.

Looking at the specification you will notice Swing Low for the INA293A5 is 20mV from GND with a 10kΩ load.  So taking this into account the minimum Vsense you can measure is 20mV/500 = 40µV.  Assuming the worst case of 20µV offset we would need 60µV at the input to overcome VOS and Swing low.  With Rshunt = 25mΩ you would need to apply 2.4mA to get a valid result.  This worst case but you need to account for it.

As for calibration you cannot use 0A input current for the same reason mentioned above where the output is not valid until it does above Swing Low.  To combat the swing low you could add a series resistor to create an offset but then you are adding an additional offset and gain error.  If calibration is needed two know currents should be used to calibrate both the error from Rshunt and gain error along with offset.

Our most accurate part his the INA229/INA228 the tradeoffs are that it is digital and the bandwidth is slower.  The other think is you could measure the full range with one device.  It is also bidirectional so swing to low will not be an issue.  You could easily see the difference by adding it to the comparison table mentioned below.

CALCULATION TOOL

Current Sense Amplifier Comparison and Error Tool (Rev. C)

SBOR020C.ZIP (568 KB)