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TLC2652

Rick Bogdan
Intellectual 930 points
Other Parts Discussed in Thread: TLC2652

We’re using the TLC2652  in a hybrid. It is hooked up to +/-5VA and must pass both positive and negative signals. The question is, would it be better to hook up the S/H caps to AGND or -5VA (VDD-)? The app note says VDD- but intuitively it seems that capacitor and/or leakage current would be unbalanced from positive to negative input voltage swings.

  • 0
    TI__Guru* 93105 points

    Hi Rick,

    The TLC2652 data-sheet regarding CXA, CXB states: "These capacitors should be located as close as possible to the CXA and CXB pins and returned to either VDD− or C RETURN. On many choppers, connecting these capacitors to VDD− causes degradation in noise performance. This problem is eliminated on the TLC2652." All CXA, CXB  connections in the data-sheet are to VDD- and is certainly the way characterization was accomplished. Therefore, the performance will meet the data-sheet specifications connected as such. Certainly they can be connected to common but the TLC2652 performance has not been characterized in that case.

    There may be some performance benefit if the two capacitors are high quality, balanced devices. An X2Y capacitor provides inherently close matching between the two capacitors contained within the structure. A NPO dielectric provides low leakage and good thermal-related capacitance stability. They are available from Johanson Dielectrics and others.

    Regards, Thomas

    PA - Linear  Engineering Applications