Datasheet

Lo L 3dB C att Ls
Ro R 3dB C att Rs
= + - ´ + ´
= + - ´ + ´
( )
( )
Lt L 3dB C 3dB Ls Rs
Rt R 3dB C 3dB Ls Rs
= + - ´ + - ´ - -
= + - ´ + - ´ +
TAS5548
SLES270 –NOVEMBER 2012 www.ti.com
3.11 Stereo Downmixes/(or Fold-Downs)
3.11.1 Left Total/Right Total (Lt/Rt)
Lt/Rt is a downmix suitable for decoding with a Dolby Pro Logic upmixer to obtain 5.1 channels again.
Lt/Rt is also suitable for stereophonic sound playback on a hi-fi or on headphones.
where Ls and Rs are phase shifted 90° (5)
3.11.2 Left Only/Right Only (Lo/Ro)
Lo/Ro is a downmix suitable when mono compatibility is required. Lo/Ro destroys front/rear channel
separation information and thus a Dolby Pro Logic upmixer will not be able to properly extract 5.1
channels again.
where att = –3 dB, –6 dB, –9 dB or 0 dB (6)
3.12 Output Mixer
The TAS5548 provides an 8×2 output mixer for channels 1, 2, 3, 4, 5, and 6. For channels 7 and 8, the
TAS5548 provides an 8×3 output mixer. These mixers allow each output to be any mix of any two (or
three) signal-processed channels. The control parameters for the output crossbar mixer are programmable
via the I
2
C interface. All of the TAS5548 features are available when the 8×2 and 8×3 output mixers are
configured in the pass-through output mixer configuration, where the audio data from each DAP channel
maps directly to the corresponding PWM channel (i.e., DAP channel 1 to PWM channel 1, etc).
When mixing or remapping DAP channels to different PWM output channels there are limitations to
consider:
• Individual channel mute should not be used.
• The sum of the minimum channel volume and master volume should not be below –109 dB.
32 TAS5548 DAP Architecture Copyright © 2012, Texas Instruments Incorporated
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