INA823: Help reviewing my 4–20 mA current input design using INA823 (single supply 3.3V)

Ivan Vargas

Part Number: INA823
Other Parts Discussed in Thread: ADS1115

Hello TI team,
I am designing an industrial analog input stage to measure 4–20 mA signals using a 100 Ohm shunt resistor (resulting in 0.4 V to 2.0 V).

I plan to use the INA823, powered from 3.3 V, configured for unity gain (G = 1), and connect its output to an ADS1115 ADC set to ±2.048 V input range (PGA = 2.048 V).

The input signals come from sensors located 5–10 meters away from the equipment connector, so I need good noise immunity, high CMRR, and stable operation in industrial environments (24 V field systems).

Is the INA823 recommended for this kind of 4–20 mA industrial input application at 3.3 V?

Or would you suggest another amplifier that offers better performance for low-noise, high-CMRR operation with long differential cables?

Thank you for your guidance.
Best regards,

10 days ago

+1 Robert Clifton56 8 days ago

TI__Mastermind 28090 points

Hi Ivan,

There're a few concerns I have with this design:

The output capacitance is very high. This could cause instability issues. I recommend including an Riso resistor or decreasing the output capacitance to 1nF.
It's recommended that C2 is 10 times larger than C3 and C4 from a filter design standpoint.
1. I recommend looking at the Analog Engineer's Calculator tool to get the correct values:
Did you verify the output range using Analog Engineer's Calculator tool?

The INA823 isn't the concern with this design to me. You mentioned degraded CMRR concerns but without a targeted spec, I can't say whether or not this is a good solution for you or not.

Let me know if you have any additional questions.

Best Regards,

Robert Clifton

+1 Gerhard Kreuzer 8 days ago in reply to Robert Clifton56

Expert 2630 points

Hi,

I do it like this and get precise results (fg ~ 10Hz, which is gk for my application). Its a Sallen-Key filter, just alter the values to meet your specs.

With best regards

Gerhard

4-20mA Input WiFi or Zigbee.pdf

0 Robert Clifton56 7 days ago in reply to Gerhard Kreuzer

TI__Mastermind 28090 points

Hi Gerhard,

Understood! Thanks for clarifying.

Best Regards,

Robert Clifton

0 Ivan Vargas 7 days ago in reply to Robert Clifton56

Prodigy 85 points

Hello Robert and Gerhard,
Thank you very much for your responses; they help us a lot with our design.
Best regards!

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INA823: Help reviewing my 4–20 mA current input design using INA823 (single supply 3.3V)