3 Replies Latest reply: Apr 4, 2012 11:39 AM by Reemo RSS

    AD8264 crosstalk spec?

    dlewis

      What is the crosstalk specification? or is there any test data on crosstalk between the analog channels on the AD8264?

       

      Thanks in advance

       

      Dave

        • 1. Re: AD8264 crosstalk spec?
          harryh

          dlewis,

           

            There is a figure 52 on the AD8622/8624 datasheet that shows the crosstalk on the dual.

          For any part from any manufacturer, it is important to know how it was tested.  If you consider

          one of the sections to be the transmitter, and another section to be the receiver, then you want

          a heavy load on the transmitter, and no load on the receiver.  With what we have learned about

          layout in the past 30-40 years, the duals and quads today are pretty good.  Because of this,

          the interference from the transmitter is very small, so you want to take gain in the receiver.

          Note that figure 52 uses a 10k load on the transmitter.  The AD8622/8624 is a low power part,

          so the spec tables have Voh and Vol specified with 10k and 100k loads.  Thus, fig 52 uses

          a 10 load.  The gain on the receiver is +101.  When we graph the data, we take this into account,

          so the dB scale is input refered.

           

          The low frequency crosstalk is a thermal effect, the power dissipation in the output stage of the

          transmitter travels across the die and unbalances the input stage on the receiver.  The high frequency

          cross talk is generally a capacitive effect, both in the test setup, but also the capacitance to substrate

          for all the transistors in a junction-isolated part.

           

          Another disadvange of using quads, especially with active filters, is you wind up with 20 passives

          crowded around a tiny package, and the pc board trace to trace capacitance is a killer.

           

          If you need extremely good numbers, then using duals or even singles would be the way to go.

          See the article(s) below for more details.

           

          Harry

           

          http://www.eetimes.com/design/analog-design/4210663/Op-amps--to-dual-or-not-to-dual---Part-1-of-2-

           

          http://www.eetimes.com/design/analog-design/4210881/Op-amps--to-dual-or-not-to-dual---Part-2-of-2-

          • 2. Re: AD8264 crosstalk spec?
            dlewis

            Hi Harry

             

            Thanks but I was asking about the AD8264 quad differential VGA Amplifier not the AD8624?

             

            Thanks

             

            Dave

            • 3. Re: AD8264 crosstalk spec?
              Reemo

              Hi Dave,

               

              Unfortunately, we don't have any test data for crosstalk on the AD8264. Of course, we would design it to minimize crosstalk as much as possible, but we have no data to quantify that for you. If you run into any issues, please do let us know and we'll work with you on it..

               

              Reemo