INA229: nA level current variation detection

Roy,

Thanks for the question and using the E2E forum.

Theoretically, yes, the INA229 would be able to measure down into the nA range, depending on your maximum expected measured current. You would need to make sure your shunt resistor is sized appropriately to make sure you could measure your nA. Your biggest challenge will be the input bias current of the device and the additional error that will create at your desired level. We specify the INA229 with a maximum I_b of 2.5nA, so you'll just need to be aware of the potential inaccuracies at these low levels.

However, realistically this would require such a large shunt resistor, it would drastically impact your maximum measurable current. The INA229 has an input offset of 1uV. To measure 1nA with 1uV, the shunt would need to be 1kΩ. This error would be on top of the current you are really trying to measure, which means you'd have ~100% error at this level. To overcome that, you'd need to keep increasing the size of the shunt just to remedy the input errors of the device.

We do have some I2C devices on the same I_b level as the IAN229, like the INA228, with the same 2.5nA I_b specification, but the same concerns as above would still apply.

Please let us know if you have any other questions.

Louis