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Initial Design for DAQ system

Category: Hardware
Product Number: AD9288

I am looking to get some feedback on this below proposed design for a DAQ system.  Some signals would be in the mV range while others would be needed to be attenuated.  A microprocessor would control the relays and additionally a bias source to keep the signal in range. I have not included the feedback on the op amps but I plan to use all non-inverting with no amplification on the buffer.

AFE

I plan on pretty closely following the reference design for the AD8372 with one difference being I don't see the need for the 1:1 transformer as it is already buffered.

AD8372 reference

Is there any fundamental flaw or advantage to any potential changes?  Any feedback would be much appreciated.  I have greater confidence on the digital side of things.

  • Hi,

    In designing a front-end circuit, you must first consider the ADC's common-mode input voltage specification. For AD9288, that is 0.3*Vd so if you use a Vd of 3.0V that corresponds to 900mV common mode bias. If not implemented, it would cause performance degradation. The ADA4930 is a good choice to use as the ADC driver since its Vocm input range is within the 900mV requirement. 

    The transformer is inherently ac-coupled and provides a quick and easy way to translate from a single-ended to a differential circuit. If you use a dc-coupled application through this buffer, keep in mind that input common mode should be kept throughout the signal chain to avoid conflicts. In cases where the output of the driver differs significantly from the required ADC input common mode voltage, ac coupling connection is used between the driver output and ADC input.

    Regards,

    Meriam