lm49350rl National Semiconductor Corporation, lm49350rl Datasheet - Page 50

• Manufacturer Part Number: lm49350rl
• Description: High Performance Audio Codec Sub-system With A Ground-referenced Stereo Headphone Amplifier & An Ultra Low Emi Class D Loudspeaker Amplifier With Dual I2s/pcm Digital Audio Interfaces
• Manufacturer: National Semiconductor Corporation

23.0 Digital Mixer Control Registers
Digital Mixer
The LM49350’s digital mixer allows for flexible routing of digital audio signals between both audio ports, DAC, and ADC. This mixer
handles which digital data path (Port1 RX data, Port2 RX data, or ADC output) is routed to the DAC input. The digital mixer also
selects the appropriate digital data path (Port1 RX data, Port2 RX data, ADC output, DAC DSP output, or ADC DSP output) that
is used for data transmission on Audio Port 1 and 2. Audio inputs to the digital mixer can be attenuated down to -18dB to avoid
clipping conditions.
Another key feature of the digital mixer is sample rate conversion (SRC) between audio ports. This allows simultaneous operation
of the dual audio ports even if each port is operating at a different sample rate. The LM49350 can be used as an audio port bridge
with SRC capability. The digital mixer allows either straight pass through between audio ports or, if desired, DSP effects can be
added to the digital audio signal during audio port bridge operation. The digital mixer automatically handles stereo I
2
S to mono
PCM conversion between audio ports and vice versa.
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FIGURE 15: Digital Mixer
The LM49350 includes two separate and independent DSP blocks, one for the DAC and the other for the ADC. The digital mixer
also allows both DSP blocks to be cascaded together in either order so that the DSP effects from both blocks can be combined
into the same signal path. For example, the 5 band parametric EQ of each DSP block can be combined together to form a 10 band
parametric EQ for added flexibility.
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