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AD vs BD modulation

chrylis
Prodigy 140 points
Other Parts Discussed in Thread: TAS5707

I'm designing a board with the TAS5707, and I'm trying to figure out the better modulation method to use.  Looking through the datasheet and the LC filter recommendations, it seems to me that BD is generally better than AD all around, but it's a bit more complicated to implement inside the amplifier and thus not supported in some older/lower-cost chips.  Is this correct, or am I missing a tradeoff?

  • 0
    TI__Guru**** 189399 points

    Hi, Chrylis,

    The major trade-off with using BD is that there is common-mode switching with no/low inputs, and this can result in more difficult EMC problems to solve.

    The good news is the output filter configuration is nearly the same for the two, so you can easily test the two modulation schemes when you get your protos back.

    And, yes, BD is more difficult to implement in silicon, basically, we need two complete signal paths for BD.

    -d2

  • 0 in reply to Don Dapkus
    Prodigy 140 points

    The application I'm experimenting with (wall/ceiling audio) is expected to have significant powered cable runs, in the range of 3-10m.  Am I better off just putting a slightly more complicated filter on my board and sticking with AD to reduce EM radiation?