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

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    •  Analog Employees 
    on May 22, 2020 3:40 AM 7 months ago in reply to

    Hi Nidhi P. Shetty,

    In that case you need to lower the differential bandwidth of the filter to cutoff the signals from 1.2kHz and higher. The Differential BW and Common-mode bandwidth is given by the formula (from AD8226 datasheet):

    You can still start with R = 1kohms as this is close to the maximum resistive load of AD5420 (which is 1.2kohm). With that you can set the CD to 80nF and CC to 8nF. you'll have a differential BW of around 950Hz, let me know if this works for you. Also, what's the configuration of the Iout of your AD5420?
    Apologies for the delayed response.

    Best Regards,