ADS1130: ADS1130 - AINP/AINN Input Current

Gilberto Ermacovitch

Part Number: ADS1130

I would like to confirm that the input current on the AINP and AINN pins is ±2nA. Therefore, adding 10-ohm ±20% PTC protection resistors should not affect the measurements.

What would be an alternative to protect the inputs against a permanent 20V overvoltage?

BR
Gilberto

11 months ago

0 Keith Nicholas 11 months ago

TI__Guru 52430 points

Hello Gilberto,

Yes, you are correct. The input current is typical +/-2nA for the ADS1130.

In general, if you use a large enough value resistor to limit current to less than 10mA in a fault condition (using the ADC internal ESD diodes to clamp the input voltage), then you will not damage the device. In your case, since the ADS1130 operates from 5V analog, and you want to protect to 20V, you would need approximately:

Rin=(20V-5V)/10mA=1.5kOhm.

Allowing for some margin, round this value up to 2kOhm. This will result in a voltage error due to the input current of the ADC of about 4uV, which is about the same error as the typical offset voltage of the ADS1130.

You can also use a combination of clamp diodes and input resistance to further protect the device, but most protection diodes will have higher leakage current than 2nA. Ultimately, it is a trade-off between input over-voltage protection and accuracy. Take a look at the TI Precision Lab series on input protection for delta-sigma ADCs.

https://www.ti.com/video/series/precision-labs/ti-precision-labs-analog-to-digital-converters-adcs.html

https://www.ti.com/video/6303631504001

https://www.ti.com/video/6304810717001

https://www.ti.com/video/6305534045112

Regards,
Keith Nicholas
Precision ADC Applications

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ADS1130: ADS1130 - AINP/AINN Input Current