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Hi team,

My customer would like to design one solution that can measure uA current measurement solution.

The specification is measuring 0~50mA current and the current shunt resistor will be 10mohm~100mohm.

The resolution they expect is 1uA.

Thanks

• Hi Paul,

If your customer uses a 10mΩ resistor for 50mA, that is a 0.5mV output voltage that will be applied to the ADC. The dynamic range required is 50mA  / 1uA = 50,000. So that means the noise required by the ADC is 0.5mV / 50000 = 10nV. I can tell you that we do not have any ADCs that can offer 10nV of peak-to-peak noise performance, but we do have some that offer 10nVRMS noise performance.

If the customer uses a 100mΩ resistor, that is a 5mV output voltage and 100nV of noise.

To meet these demanding noise targets, I would suggest the ADS1260. Below are portions of the ADS1260 noise table showing the max data rate / filter combination where the customer can meet 10nVRMS and 100nVRMS noise performance. I assume the maximum gain of 128 will be used due to the very small signals.

I would also wonder if it is possible to increase the size of the shunt in order to get more dynamic range. Increasing the shunt size also increases the output voltage measured by the ADC, which in turn relaxes the noise requirements.

Let me know if you have any additional questions.

ADS1260 noise <10nVRMS = sample up to 5 SPS using G = 128

ADS1260 noise <100nVRMS = sample up to 400 SPS using G = 128

-Bryan