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INA186: INA186A5IDCKR

Simon Chang
Prodigy 10 points
Part Number: INA186

We use the INA186 in our design and we have some spike on the output of INA186. We check the spike is come from the voltage noise from our system and we add an RC filter on the output of INA186 to fix this issue. Below is our simplified block diagram, and I just have a question and need our help to confirm the the RC filter will cause any impact or not? 

 

  • 0
    TI__Mastermind 18780 points

    Simon,

    Filtering is discussed in section 8.1.3 of the datasheet. As we mention, filtering the input filters out differential noise across the sense resistor, but high-frequency, common-mode noise is better addressed by an RC filter from the OUT pin to ground. The main issues to take into account are that your resistor is of sufficient size to ensure sufficient isolation of the capacitor from the output stage, and that any current drawn by the load will manifest as an external voltage drop from the INA186 OUT pin to the load input over this resistor. 

  • 0 in reply to Carolus Andrews
    Prodigy 10 points

    Hi Carolus, Thnaks for your feedback, but I still have one concern about the datasheet that show in the electrical characteristics on the out portion, mention the "Maximum capacitive load" in our case will cause the circuit oscillation ot not, I'm confuse the describe in this. Thank you!

  • +1 in reply to Simon Chang
    TI__Mastermind 18780 points

    Simon, 

    The output pin of the INA186, like any amplifier, can only drive so much capacitance directly before becoming unstable. This is discussed in depth in section 4 of this app note, and is due to loading effects of the capacitance interacting with the inductive portion of the output impedance of the output stage.

    That said, 10kΩ as the customer plans to implement in the above should be more than enough isolation resistance to effectively isolate the LPF capacitance from the output node. This should be fine.