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PDF LM4546B Data sheet ( Hoja de datos )
| Número de pieza | LM4546B | |
| Descripción | AC 97 Rev 2 Multi-Channel Audio Codec | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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September 2006
LM4546B
AC ’97 Rev 2 Multi-Channel Audio Codec with Sample
Rate Conversion and National 3D Sound
General Description
The LM4546B is an audio codec for PC systems which is
fully PC99 compliant and performs the analog intensive
functions of the AC ’97 Rev 2.1 architecture. Using 18-bit
Sigma-Delta ADCs and DACs, the LM4546B provides 90 dB
of Dynamic Range.
The LM4546B was designed specifically to provide a high
quality audio path and provide all analog functionality in a PC
audio system. It features full duplex stereo ADCs and DACs
and analog mixers with access to 2 stereo and 2 mono
inputs. Each mixer input has separate gain, attenuation and
mute control and the mixers drive 1 mono and 1 stereo
output, each with attenuation and mute control. The
LM4546B supports National’s 3D Sound stereo enhance-
ment and a comprehensive sample rate conversion capabil-
ity. The sample rate for the ADCs and DACs can be pro-
grammed separately with a resolution of 1 Hz to convert any
rate in the range 4 kHz – 48 kHz. Sample timing from the
ADCs and sample request timing for the DACs are com-
pletely deterministic to ease task scheduling and application
software development. These features together with an ex-
tended temperature range also make the LM4546B suitable
for non-PC codec applications.
The LM4546B features the ability to connect several codecs
together using the Extended AC Link configuration of one
dedicated serial data signal to the Controller per codec.
LM4546B systems support up to 8 simultaneous channels of
streaming data on Input Frames (Codec to Controller) while
Output Frames (Controller to Codec) carry 2 streams to
multiple codecs. The LM4546B may also be used in systems
with the National LM4550 to support up to 6 simultaneous
channels of streaming data on Output Frames.
The AC ’97 architecture separates the analog and digital
functions of the PC audio system allowing both for system
design flexibility and increased performance.
Key Specifications
n Analog Mixer Dynamic Range
n DAC Dynamic Range
n ADC Dynamic Range
97 dB (typ)
89 dB (typ)
90 dB (typ)
Features
n AC ’97 Rev 2.1 compliant
n High quality Sample Rate Conversion from 4 kHz to 48
kHz in 1 Hz increments
n Multiple codec support
n National’s 3D Sound stereo enhancement circuitry
n Advanced power management support
n Digital 3.3V and 5V supply options
n Extended Temperature: −40˚C ≤ TA ≤ 85˚C
Applications
n Desktop PC audio systems on PCI cards, AMR cards, or
with motherboard chips sets featuring AC Link
n Portable PC systems as on MDC cards, or with a
chipset or accelerator featuring AC Link
n General and Multi-channel audio frequency systems
n Automotive telematics
© 2006 National Semiconductor Corporation DS201233
www.DataSheet.in
www.national.com
1 page  
Electrical Characteristics (Notes 1, 5) The following specifications apply for AVDD = 5V, DVDD = 3.3V,
Sampling Frequency (Fs) = 48 kHz, single codec configuration, (primary mode) unless otherwise noted. Limits apply for TA=
25˚C. The reference for 0 dB is 1 Vrms unless otherwise specified. (Continued)
Symbol
Parameter
Conditions
TCO Output Valid Delay
TRISE
Rise Time
TFALL
TRST_LOW
TRST2CLK
TSH
TSYNC2CLK
TS2_PDOWN
Fall Time
RESET# active low pulse width
RESET# inactive to BIT_CLK start
up
SYNC active high pulse width
SYNC inactive to BIT_CLK start up
AC Link Power Down Delay
TSUPPLY2RST Power On Reset
TSU2RST
TRST2HZ
Setup to trailing edge of RESET#
Rising edge of RESET# to Hi-Z
Output Delay of SDATA_IN from rising
edge of BIT_CLK
BIT_CLK, SYNC, SDATA_IN or
SDATA_OUT
BIT_CLK, SYNC, SDATA_IN or
SDATA_OUT
For Cold Reset
For Cold Reset
For Warm Reset
For Warm Reset
Delay from end of Slot 2 to BIT_CLK,
SDATA_IN low
Time from minimum valid supply levels
to end of Reset
For ATE Test Mode
For ATE Test Mode
LM4546B
Typical Limit
(Note 6) (Note 7)
Units
(Limits)
5.2 15 ns (max)
6 ns (max)
6 ns (max)
1.0 µs (min)
271 162.8 ns (min)
1.0
162.8
µs (min)
ns (min)
1 µs (max)
1 µs (min)
15 ns (min)
25 ns (max)
Note 1: Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is
functional, but do not guarantee specific performance limits. Electrical Characteristics state DC and AC electrical specifications under particular test conditions which
guarantee specific performance limits. This assumes that the device is within the Operating Ratings. Specifications are not guaranteed for parameters where no limit
is given, however, the typical value is a good indication of device performance.
Note 2: Human body model, 100 pF discharged through a 1.5 kΩ resistor.
Note 3: Machine Model, 220 pF – 240 pF discharged through all pins.
Note 4: The maximum power dissipation must be derated at elevated temperatures and is dictated by TJMAX, θJA, and the ambient temperature TA. The maximum
allowable power dissipation is PDMAX = (TJMAX– TA)/θJA or the number given in Absolute Maximum Ratings, whichever is lower. For the LM4546B, TJMAX = 150˚C.
The typical junction-to-ambient thermal resistance is 74˚C/W for package number VBH48A.
Note 5: All voltages are measured with respect to the ground pin, unless otherwise specified.
Note 6: Typicals are measured at 25˚C and represent the parametric norm.
Note 7: Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level).
Note 8: Loopthrough mode describes a path from an analog input through the analog mixers to an analog output.
Note 9: These specifications are guaranteed by design and characterization; they are not production tested.
Note 10: Out of band energy is measured from 28.8 kHz to 100 kHz relative to a 1 Vrms DAC output.
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5 Page 
Pin Descriptions (Continued)
ANALOG I/O (Continued)
Name
Pin I / O
Functional Description
Left Stereo Channel Output
LINE_OUT_L
35
This line level output (1 Vrms nominal) is fed from the left channel of the Stereo Mix signal
O
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
LINE_OUT_R
36
This line level output (1 Vrms nominal) is fed from the right channel of the Stereo Mix signal
O
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
MONO_OUT
37
O 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.
Name
Pin
XTL_IN
2
XTL_OUT
3
SDATA_OUT
5
BIT_CLK
6
SDATA_IN
8
I/O
I
O
I
I/O
O
DIGITAL I/O AND CLOCKING
Functional Description
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 (VIH, VIL).
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
LM4546B codec. These frames can contain both control data and DAC PCM audio data. This
input is sampled by the LM4546B 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 LM4546B codec to an AC ’97 Digital
Audio Controller. These frames can contain both codec status data and PCM audio data from
the ADCs. The LM4546B clocks data from this output on the rising edge of BIT_CLK.
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