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ADS1263EVM-PDK: ADS data is not proper

tushar gajjar
Prodigy 60 points
Part Number: ADS1263EVM-PDK
Other Parts Discussed in Thread: ADS1263

Tool/software:

Hi ,

I am using ADS1263EVM-PDK. I want to measure current using differential input,  voltage across shunt resistor( 1 ohm) .  used INA0 and INA1 .

i am using GUI tool. the full scale voltage is 5 v ,  taking internal reference voltage +2.5 v and -2.5 v. using gain 32, sinc5 filter , 38400 SPS.

i am getting below reading as compared to dmm 6500

Shunt val = 1 ohm
Load Value shunt current(uA)(ADC1)
Dmm current(uA)
5.9 k 874 834
12.48 k 415 399
25 k 205 201
50 k 101 98
100 k 44 49
200 k 22 25
508 k 8 9
1 m 650nA 4.9

we want measure current in range 1uA to 3A

you can see the current value is not matching to the dmm 6500

please help us to solve

Thanks ,

Tushar Gajjar

  • 0
    TI__Mastermind 45715 points

    Hi Tushar Gajjar,

    Welcome to the E2E forum.

    When you set the data rate to 38400sps and the gain to 32 on the ADS1263, the noise from the ADC is around 24.435uVpp (3.276uVrms) , see the following noise table from the ADS1263 datasheet. When the current you wanted to measure is 4.9uA, the voltage across the shunt is 4.9uA*1ohm=4.9uV that is much less than the noise of the ADC. When the current you wanted to measure is 834uA, the voltage across the shunt is 834uA*1ohm=834uV, the noise is still significant.

    To do a precise measurement, you will have to reduce the data rate of your ADC, and also you should do a calibration and enable the global chop option to minimize the offset error. Notice that 1uA is very critical because the voltage is only 1uV across the 1ohm shunt resistor, you will have to reduce your data rate to a much lower level that you can accept, see the noise at the low data rate in the table 8-1.

    BR,

    Dale