AD8226 filter circuit


I was referring to MT-070 to ad filter circuit to AD8226.


IOUT_ AD5420 and IOUT_ AD5420_R are two terminal of resistor in a 4-20mA current loop where I'm sensing. As HART signals also flows through my 4-20mA loop, Is there any dependency while selecting filter to this instumentation amplifier with respect to frequency. HART signals at loop(FSK signal) will be at frequency 1.2KHz and 2.2KHz. Please help me out.


Nidhi P Shetty

Parents Reply
  • 0
    •  Analog Employees 
    on May 12, 2020 1:51 AM 8 months ago in reply to

    Hi Nidhi P. Shetty

    Thanks for considering AD8226 on your design.
    I would think that you'll want this 1.2kHZ to 2.2kHz signal be detected on the AD8226.

    Checking out our Designer's guide to instrumentation Amplifiers, page 5-14 shows the general rules in selecting the RC input filter. For the resistor values, looking at the AD5420 it can only handle about 1.2kohms load, I would suggest you start there and adjust Cc and CD accordingly (Differential BW should be 10 times higher than the desired frequency which in your case is 2.2kHz signal).

    Page 5-12 to 5-23 provides a lot of additional information on RFI filters.
    Let me know if this answers your question or if you have more concerns Nidhi P. Shetty.

    Best Regards,