Ad7768-1 external component selection

Just to help clarify things for me, I’m designing a circuit for a general purpose daq application (goal being lowest achievable noise from ~1ksps to ~64ksps) with the ad7768-1, ada4254, and TBD external reference. Looking at the datasheet for the amplifier, it says that it can be connected directly to the ad7768-1 however it’s 3db bandwidth is significantly lower than the input switching frequency of the AD converter. When selecting an external voltage reference, as well as the input amplifier, should I be looking at their output impedance at 2*fmod when determining the error budget? I’m trying to determine if buffers are actually required. For a second question, the datasheet section for the ad7768-1 VCM output mentions requiring a low pass filter. Should the target bandwidth be equal to the ODR Nyquist frequency? Is this bandwidth for responding to the VREF current switching transients?

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  • Thank you, I didn’t know that tool existed! That and AN-1384 were pretty helpful.  For the reference, I’d like to use a max6341(flat band is ~25nv/sqrt(Hz)) with an external buffer; maybe ada4897-1. Signal BW will be 32khz. Will there still be any charge injection to worry about at ~16Mhz fast mode with the ad7768 full-buffer mode active? The app note just shows as Sallen key with no component values.