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ADS1292 - Vcap reference

Bruce McMillan
Intellectual 310 points

Other Parts Discussed in Thread: ADS1292, ADS1298, ADS1298ECGFE-PDK

The circuit for the ADS1298ECGFE has all "Vcap" bypass caps connected to AVss.  However in the ADS1292ECGFE they are shown connected to DGND. In the case  of the ADS1292ECGFE board it doesn't matter because AVss & DGnd are connected.

So can you confirm that for the general case for the ADS1292, Vcaps are to be connected to AVss (or not?)

bruce

  • 0
    TI__Guru**** 182651 points

    Hi Bruce,

    VCAP connections on the ADS1298 should be referred to VREFN of the ADS1298 (or ADS1292), which is always the 'most negative' rail.  In a bipolar supply situation, the reference is based from Vss to VREFP, which is how the ADS1298ECGFE-PDK is setup.  For the ADS1292ECGFE-PDK, its a unipolar supply with all Vss nodes tied to ground.