lm4546a National Semiconductor Corporation, lm4546a Datasheet - Page 11

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lm4546a

Manufacturer Part Number
lm4546a
Description
Ac ?97 Rev 2 Multi-channel Audio Codec With Sample Rate Conversion And National 3d Sound
Manufacturer
National Semiconductor Corporation
Datasheet
SDATA_OUT
LINE_OUT_R
LINE_OUT_L
Pin Descriptions
MONO_OUT
SDATA_IN
XTL_OUT
BIT_CLK
XTL_IN
Name
Name
Pin
2
3
5
6
8
Pin
35
36
37
I / O
I / O
I/O
O
O
I
I
O
O
O
(Continued)
Functional Description
Left Stereo Channel Output
This line level output (1 Vrms nominal) is fed from the left channel of the Stereo Mix signal
from MIX2 via the Master Volume register, 02h. The LINE_OUT_L amplitude can be muted
(along with LINE_OUT_R) or adjusted from 0 dB to -46.5 dB in 1.5 dB steps.
Right Stereo Channel Output
This line level output (1 Vrms nominal) is fed from the right channel of the Stereo Mix signal
from MIX2 via the Master Volume register, 02h. The LINE_OUT_R amplitude can be muted
(along with LINE_OUT_L) or adjusted from 0 dB to -46.5 dB in 1.5 dB steps.
Mono Output
This mono line level output (1 Vrms nominal) is fed from either a microphone input (MIC1 or
MIC2, after boost amplifier) or from the mono sum of the left and right Stereo Mix 3D
channels from MIX1. The optional National 3D Sound enhancement can be disabled (default)
by the 3D bit (bit D13) in the General Purpose register, 20h. Choice of input is by the MIX bit
(D9) in the same register. MIX=0 selects a microphone input. Output level can be muted or
adjusted from 0 dB to -46.5 dB in 1.5 dB steps via the Mono Volume register, 06h.
24.576 MHz crystal or oscillator input
To complete the oscillator circuit use a fundamental mode crystal operating in parallel
resonance and connect a 1MΩ resistor across pins 2 and 3. Choose the load capacitors
(Figure 2, C1, C2) to suit the load capacitance required by the crystal (e.g. C1 = C2 = 33 pF
for a 20 pF crystal Assumes that each ’Input + trace’ capacitance = 7 pF).
This pin may also be used as the input for an external oscillator (24.576 MHz nominal) at
standard logic levels (V
This pin is only used when the codec is in Primary mode. It may be left open (NC) for any
Secondary mode.
24.576 MHz crystal output
Used with XTAL_IN to configure a crystal oscillator.
When the codec is used with an external oscillator this pin should be left open (NC).
When the codec is configured in a Secondary mode this pin is not used and may be left open
(NC).
Input to codec
This is the input for AC Link Output Frames from an AC ’97 Digital Audio Controller to the
LM4546A codec. These frames can contain both control data and DAC PCM audio data. This
input is sampled by the LM4546A on the falling edge of BIT_CLK.
AC Link clock
An OUTPUT when in Primary Codec mode. This pin provides a 12.288 MHz clock for the AC
Link. The clock is derived (internally divided by two) from the 24.576 MHz signal at the crystal
input (XTL_IN).
This pin is an INPUT when the codec is configured in any of the Secondary Codec modes
and would normally use the AC Link clock generated by a Primary Codec.
Output from codec
This is the output for AC Link Input Frames from the LM4546A codec to an AC ’97 Digital
Audio Controller. These frames can contain both codec status data and PCM audio data from
the ADCs. The LM4546A clocks data from this output on the rising edge of BIT_CLK.
DIGITAL I/O AND CLOCKING
ANALOG I/O (Continued)
IH
, V
IL
11
).
Functional Description
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