INA230: Setting the R_SHUNT value.

Charles Jeon

Expert 2975 points

Part Number: INA230
Other Parts Discussed in Thread: INA190, INA191, INA186

Hi team.

My customer want to measure nA current through INA230.

The configuration is as follows.

I think that if Rsunt is 1mohm, Ishunt is too small to be measured.

So, it would be possible to make calculations by raising Rshunt to 1 ohm.

Is there a problem when I change to 1ohm?

over 4 years ago

0 Ian Williams over 4 years ago

TI__Mastermind 27715 points

Hello Charles,

Unfortunately measuring the nA range of current is beyond the current capability of current sense amplifier ICs. This is a limitation of the input bias current, input offset voltage, and input-referred noise of these devices. Our family of capacitively-coupled input amplifier chips, including INA190, INA191, and INA186, have the lowest input bias current and can measure down to uA, but nothing that we offer can handle nA. To do that you'll need to investigate other methods such as described in this article.

Best regards,

Ian Williams
Applications Manager
Current & Magnetic Sensing

0 Ian Williams over 4 years ago in reply to Ian Williams

TI__Mastermind 27715 points

To add a little more information, typically these types of measurements are done with precision transimpedance amplifiers with fA of input bias current. Here's a cookbook circuit and an app note on photodiode current measurement.

Best regards,

Ian Williams

0 Charles Jeon over 4 years ago in reply to Ian Williams

Expert 2975 points

Thank you

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INA230: Setting the R_SHUNT value.