lm49350rl National Semiconductor Corporation, lm49350rl Datasheet - Page 59

• 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

25.0 Digital Effects Engine
Digital Signal Processor (DSP)
The LM49350 is designed to handle the entire audio signal conditioning and processing within the audio system, thereby freeing
up the workload of any other applications processor contained within the system. The LM49350 features two independent DSPs,
one for the DAC and the other for the ADC. Each DSP is fully featured and performs as a professional quality digital audio effects
engine. The data paths on each DSP engine are 24 bits wide for ultimate flexibility. Both DSP engines feature digital volume control,
automatic level control (ALC), digital soft clip compression, and a 5-band parametric EQ. The ADC DSP engine adds a dedicated
high-pass filter to reduce wind noise or pop noise during uplink. The DAC DSP engine adds a digital 3D algorithm that allows for
stereo widening of the original audio signal. The effects chain of each DSP engine is shown by the diagrams below.
The ADC and DAC DSP engines can be cascaded together in any order via the digital mixer to combine different audio effects to
the same signal path. For example, a signal can be processed with high-pass filtering from the ADC effects engine with 3D stereo
widening from the DAC effects engine. The 5-band parametric EQs from each DSP engine can be combined to form a single 10-
band parametric EQ or a single 5-band parametric EQ with ±30dB (instead of ±15dB) gain control for each band.
Bits
Bits
0
1
2
3
4
0
1
2
3
4
ADC_SCLP_ENB
ADC_SCLP_ENB
ADC_HPF_ENB
ADC_ALC_ENB
DAC_ALC_ENB
ADC_EQ_ENB
DAC_EQ_ENB
ADC_PK_ENB
DAC_PK_ENB
DAC_3D_ENB
Field
Field
This enables the ADC's High Pass Filter.
This enables the ADC's Auto Level Control.
This enables the ADC's Peak Detector.
This enables the ADC's 5-band Parametric EQ.
This enables the ADC's Soft Clip Feature.
This enables the DAC's Auto Level Control.
This enables the DAC's Peak Detector.
This enables the DAC's 5-band Parametric EQ.
This enables the DAC's Stereo Widening Circuit.
This enables the DAC's Soft Clip Feature.
FIGURE 20: ADC DSP Effects Chain
FIGURE 21: DAC DSP Effects Chain
TABLE 44. ADC EFFECTS (0x70h)
TABLE 45. DAC EFFECTS (0x71h)
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Description
Description
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