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# INA169: Output error in INA169 amplifier for 24uV input voltage

Part Number: INA169
Other Parts Discussed in Thread: INA186

Hi Team,

We were planned to use INA169 amplifier to measure 1mA-4A load current.

Datasheet specify the total output error to typically be 0.5% and in worst case 2% for Vsense=100mV.

In our design, Vsense will be varying from 24uV to 100mV.

I couldn't figure out the error percentage from the datasheet graph Figure 4. Total Output Error vs VIN

What is the Output error to be considered for these ranges.

Whether this error can be calibrated? If so, explain how to calibrate this error.

Request you to provide your support.

Regards,

D.Meenalochini.

• Hi,

the input offset error voltage of INA169 is up to +/-1mV. This is 40 times bigger than your minimum input voltage across the shunt of 25µV. Therefore, with your 25mR shunt 1mA cannot be measured without huge error.

Kai

• Hi Kai,

I can understand the impact of error during 25uV input.

What is the minimum input voltage that can be sensed by INA169 with minimum error (less than 0.1%).

We have a limitation in circuit that ADC output voltage can't exceed more than 3V even during Maximum of 4A current.

Please share your suggestion on implementing the 1mA-4A current sense circuit using INA169.

Regards,

D.Meenalochini.

• Hi,

As Kai mentioned (thank you Kai), it is challenging to sense current over such wide range and maintain accuracy at the same time. You alluded to the possibility of calibration, which will help.

However for a -1mV offset part, theoretically it will not show a change in output until the current increases to at least 40mA (Rs=0.025Ohm). The solution is to bias the output to a nonzero value when input is 0A. Paragraph 8.2.3 talks about this technique in great detail, you might want to refer to this information.

The other alternative is to use a bidirectional device. INA186 is such an alternative which might fit the application.

Regards, Guang