INA180: Output current decreases from 125 uA to 90 uA when INA180A was powered

Jonathan Geronga

Part Number: INA180
Other Parts Discussed in Thread: LM334, , INA190, INA186

Hi Team,

The circuit of our customer is having issue in combining INA180A with LM334 below:

When the INA180 is not powered, the setpoint of the LM334 is 125 uA. When the IN180 is powered, however, the part draws current from the output and the output decreases to 90 uA. They selected the INA180 because it has a low input bias current to the inputs so they do not understand why this part is consuming 35 uA from the current driver output. Is there anything that should be aware of using these parts together?

For more information:
The customer is using a 710 ohm current sense resistor. Since I_set of the LM334 is set to 125 uA, they expect the voltage drop across this resistor to be 0.088 V.

Let us know what's your input for this issue.

Thanks!

Jonathan

over 5 years ago

0 Javier Contreras4 over 5 years ago

TI__Mastermind 29170 points

Jonathan,

The INA180 has a max input bias current in the 80µA at a VCM of 12V according to the datasheet. Also there is a figure 20 - figure 22 in the datasheet will be helpful.

Maybe they should think about the INA190, INA186.

0 Paul Gancitano over 5 years ago in reply to Javier Contreras4

Prodigy 95 points

Thanks for your reply. That is a good find. The part listing on Digikey reports the input bias as only 100 nA which is why I selected this part; perhaps this field in their product attributes is incorrect.

0 Javier Contreras4 over 5 years ago in reply to Paul Gancitano

TI__Mastermind 29170 points

Paul,

The specification of 100nA is when VCM = 0V. I believe the condition of 12V VCM is the more appropriate specification to list there. I will work on getting this fixed.

0 Javier Contreras4 over 5 years ago in reply to Javier Contreras4

TI__Mastermind 29170 points

Paul,

This has been fixed on Digikey. Even though it is correct that 100nA is the input bias current at 0V VCM the more relevant specification is the 80µA at 12V VCM.

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INA180: Output current decreases from 125 uA to 90 uA when INA180A was powered