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ADS8168: Determining RC Filter Values for INA190A4 and ADS8168

Nik Dua
Prodigy 200 points
Part Number: ADS8168
Other Parts Discussed in Thread: INA190, ADS7042, TINA-TI

Hi there,

I was planning to implement a uni-directional current sensing circuit as per attached TINA circuit schematic. 

I was wondering if the RC filter values seem reasonable for the low bandwidth on the INA190A4. I essentially used the following tech note (http://www.ti.com.cn/cn/lit/an/sbaa340/sbaa340.pdf

I'm trying to limit my sampling to a max 100ksps as the current changes are very DC. 

Thanks for your help!!

  • 0
    TI__Mastermind 36290 points
    Hello Nik,

    The ADS816x presents a much larger switched capacitive load to the amplifier than the ADC used in the cookbook circuit.

    What is your minimum sample rate that you would like to achieve? I think about the best you can achieve directly driving the ADS816x with the INA190 family is around 10ksps. Anything faster, and you will need to add an additional buffer amplifier.

    Regards,
    Keith N.
    Precision ADC Applications
  • 0 in reply to Keith Nicholas
    Prodigy 200 points

    Hi Keith,

    Thanks for the reply!

    Ideally I'd like at least 100ksps of minimum sampling rate. I've decided to configure the circuit with a buffer amplifier as per below. Would this work?

    Best,

    Nik 

  • 0 in reply to Nik Dua
    TI__Mastermind 36290 points
    Hello Nik,

    Yes, this approach will work well. I suggest following Figure 107 in the datasheet. You will still need an RC filter between the output of the INA190 and the ADC multiplexor inputs. Since the multiplexor switched capacitive load is very similar to the ADS7042 used in the cookbook circuit you mentioned before, the same RC filter should provide very similar results.

    You can simulate the performance using the TINA-TI models for all of the above parts. TI Precision Labs - ADCs provides additional details on how to use these models to design your input driver. Section 5 specifically covers the design of the input driver amplifier and the RC filter.

    training.ti.com/ti-precision-labs-adcs

    Regards,
    Keith