LM4540 National Semiconductor, LM4540 Datasheet - Page 8

• Manufacturer Part Number: LM4540
• Description: AC 97 Codec with National 3D Sound
• Manufacturer: National Semiconductor

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Pin Description
Analog I/O
LINE_OUT_R
LINE_OUT_L
MONO_OUT
LINE_IN_R
LINE_IN_L
Name
CD_R
MIC1
MIC2
Pin
(Continued)
20
21
22
23
24
35
36
37
(Continued)
I / O
O
O
O
I
I
I
I
I
Functional Description
This line level input can be routed through the Input Mux and recorded by the right ADC. In
addition, this analog input gets summed into the right output stream. The amount of CD_R
signal mixed in the right output stream can be adjusted from +12dB to −34.5dB in 1.5dB
steps as well as muted via register 12h.
Either MIC1 or MIC2 can be selected via software and routed through the Input Mux for
recording. The 20dB boost circuit is enabled/disabled via register 0Eh. Also, the amount of
mic signal mixed in the output stream can be adjusted from +12dB to −34.5dB in 1.5dB
steps as well as muted via register 0Eh.
Either MIC1 or MIC2 can be selected via software and routed through the Input Mux for
recording. The 20dB boost circuit is enabled/disabled via register 0Eh. Also, the amount of
mic signal mixed in the output stream can be adjusted from +12dB to −34.5dB in 1.5dB
steps as well as muted via register 0Eh.
This line level input can be routed through the Input Mux and recorded by the left ADC. In
addition, this analog input gets summed into the left output stream. The amount of
LINE_IN_L signal mixed in the left output stream can be adjusted from +12dB to −34.5dB in
1.5dB steps as well as muted via register 10h.
This line level input can be routed through the Input Mux and recorded by the right ADC. In
addition, this analog input gets summed into the right output stream. The amount of
LINE_IN_R signal mixed in the right output stream can be adjusted from +12dB to −34.5dB
in 1.5dB steps as well as muted via register 10h.
This is a post-mixed output for the left audio channel. The level of this output can be
adjusted from 0dB to −45dB in 1.5dB steps as well as muted via register 02h.
This is a post-mixed output for the right audio channel. The level of this output can be
adjusted from 0dB to −45dB in 1.5dB steps as well as muted via register 02h.
This line level output can be switched between outputting the post-mixed combined left and
right outputs or the mic signal. The level of this output can be adjusted from 0dB to −45dB in
1.5dB steps as well as muted via register 06h.
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