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LM4550B AC ’97 Rev 2.1 Multi-Channel Audio Codec with Stereo Headphone Amplifier, Sample
Rate Conversion and National 3D Sound
September 2006
LM4550B
AC ’97 Rev 2.1 Multi-Channel Audio Codec with Stereo
Headphone Amplifier, Sample Rate Conversion and
National 3D Sound
General Description
The LM4550B 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 LM4550B provides 90 dB
of Dynamic Range.
The LM4550B 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 4 stereo and 4 mono
inputs. Each mixer input has separate gain, attenuation and
mute control and the mixers drive 1 mono and 2 stereo
outputs, each with attenuation and mute control. The
LM4550B provides a stereo headphone amplifier as one of
its stereo outputs and also supports National’s 3D Sound
stereo enhancement and a comprehensive sample rate con-
version capability. The sample rate for the ADCs and DACs
can be programmed 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
completely deterministic to ease task scheduling and appli-
cation software development. These features together with
an extended temperature range also make the LM4550B
suitable for non-PC codec applications.
The LM4550B features the ability to connect several codecs
together in a system to provide up to 6 simultaneous chan-
nels of streaming data on Output Frames (Controller to
Codec) for surround sound applications. Such systems can
also support up to 8 simultaneous channels of streaming
data on Input Frames (Codec to Controller). Multiple codec
systems can be built either using the standard AC Link
configuration (i.e. of one serial data signal to the Controller
per codec) or using a unique National Semiconductor fea-
ture for chaining codecs together. This chain feature shares
only a single data signal to the controller among multiple
codecs.
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
n
n
n
Analog Mixer Dynamic Range
DAC Dynamic Range
ADC Dynamic Range
Headphone Amp THD+N at 50 mW
into 32Ω
97 dB
89 dB
90 dB
0.02%
(typ)
(typ)
(typ)
(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
Supports up to 6 DAC channel systems with multiple
LM4550Bs or with other National LM45xx codecs
n
Unique National chaining function shares a single
controller SDATA_IN pin among multiple codecs
n
Stereo headphone amp with separate gain control
n
National’s 3D Sound stereo enhancement circuitry
n
Advanced power management support
n
External Amplifier Power Down (EAPD) control
n
PC Beep passthrough to Line Out during Initialization or
Cold Reset
n
Digital 3.3V and 5V supply options
n
Extended Temperature: −40˚C
≤
T
A
≤
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 Audio Frequency Systems requiring 2, 4 or 6
DAC channels and/or up to 8 ADC channels
n
Automotive telematics
© 2006 National Semiconductor Corporation
DS201237
www.national.com
LM4550B
www.national.com
20123701
Block Diagram
2
LM4550B
Absolute Maximum Ratings
(Note 1)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage
Storage Temperature
Input Voltage
ESD Susceptibility (Note 2)
pin 3
ESD Susceptibility (Note 3)
pin 3
Junction Temperature
6.0V
−65˚C to +150˚C
−0.3V to V
DD
+0.3V
2000V
750
200V
100V
150˚C
Soldering Information
LQFP Package
Vapor Phase (60 sec.)
Infrared (15 sec.)
θ
JA
(typ) – VBH48A
215˚C
220˚C
74˚C/W
Operating Ratings
Temperature Range
T
MIN
≤
T
A
≤
T
MAX
(Note 4)
Analog Supply Range
Digital Supply Range
−40˚C
≤
T
A
≤
85˚C
4.2V
≤
AV
DD
≤
5.5V
3.0V
≤
DV
DD
≤
5.5V
(Notes 1, 5) The following specifications apply for AV
DD
= 5V, DV
DD
= 3.3V, Fs =
48 kHz, single codec configuration, (primary mode) unless otherwise noted. Limits apply for T
A
= 25˚C. The reference for 0 dB
is 1 Vrms unless otherwise specified.
LM4550B
Typical
(Note 6)
AV
DD
DV
DD
Analog Supply Range
Digital Supply Range
Digital Quiescent Power Supply
Current
Analog Quiescent Power Supply
Current
Digital Shutdown Current
Analog Shutdown Current
Reference Voltage
Power Supply Rejection Ratio
CD Input to Line Output, -60 dB Input
THD+N
V
O
= -3 dB, f = 1 kHz, R
L
= 10 kΩ
LINE_IN, AUX, CD, VIDEO, PC_BEEP,
PHONE
DV
DD
= 5 V
DV
DD
= 3.3 V
AV
DD
= 5 V
PR6543210 = 1111111
PR6543210 = 1111111
No pullup resistor
34
19
53
19
70
2.16
40
Limit
(Note 7)
4.2
5.5
3.0
5.5
D
IDD
A
IDD
I
DSD
I
ASD
V
REF
PSRR
V (min)
V (max)
V (min)
V (max)
mA
mA
mA
µA
µA
V
dB
Units
(Limits)
Electrical Characteristics
Symbol
Parameter
Conditions
Analog Loopthrough Mode
(Note 8)
Dynamic Range (Note 9)
THD
Total Harmonic Distortion
97
0.013
90
0.02
dB (min)
% (max)
Analog Input Section
V
IN
V
IN
V
IN
Xtalk
Z
IN
C
IN
Line Input Voltage
Mic Input with 20 dB Gain
Mic Input with 0 dB Gain
Crosstalk
Input Impedance (Note 9)
Input Capacitance(Note 9)
Interchannel Gain Mismatch
Record Gain Amplifier - ADC
A
S
A
M
Mixer Section
A
S
A
M
Step Size
Mute Attenuation(Note 9)
+12 dB to -34.5 dB
1.5
86
dB
dB
Step Size
Mute Attenuation (Note 9)
0 dB to 22.5 dB
1.5
86
dB
dB
CD Left to Right
CD Left to Right
All Analog Inputs
1
0.1
1
−95
40
3.7
0.10
10
7
Vrms
Vrms
Vrms
dB
kΩ (min)
pF
dB
3
www.national.com
LM4550B
Electrical Characteristics
(Notes 1, 5) The following specifications apply for AV
DD
= 5V, DV
DD
= 3.3V, Fs =
48 kHz, single codec configuration, (primary mode) unless otherwise noted. Limits apply for T
A
= 25˚C. The reference for 0 dB
is 1 Vrms unless otherwise specified. (Continued)
LM4550B
Typical
(Note 6)
Analog to Digital Converters
Resolution
Dynamic Range (Note 9)
Frequency Response
Digital to Analog Converters
Resolution
Dynamic Range (Note 9)
THD
Total Harmonic Distortion
Frequency Response
Group Delay (Note 9)
Out of Band Energy (Note 10)
Stop Band Rejection
D
T
A
S
A
M
THD+N
Z
OUT
Z
OUT
Discrete Tones
Step Size
Mute Attenuation(Note 9)
Headphone Amplifier Total
Harmonic Distortion plus Noise
Output Impedance (Note 9)
Output Impedance (Note 9)
Loopthrough Mode (Note 8), R
L
= 32
Ω,
f = 1 kHz, P
out
= 50 mW
HP_OUT_L, HP_OUT_R
LINE_OUT_L, LINE_OUT_R,
MONO_OUT
0 dB to -46.5 dB
Analog Output Section
1.5
86
0.02
0.65
220
2.75
500
dB
dB
%
Ω
Ω
Sample Freq. = 48 kHz
-60 dB Input THD+N, A-Weighted
V
IN
= -3 dB, f = 1 kHz, R
L
= 10 kΩ
18
89
0.01
20-21 k
0.36
-40
70
-96
1
82
Bits
dB (min)
%
Hz
ms
(max)
dB
dB
dB
-60 dB Input THD+N, A-Weighted
-1 dB Bandwidth
18
90
20
86
Bits
dB (min)
kHz
Limit
(Note 7)
Units
(Limits)
Symbol
Parameter
Conditions
Digital I/O
(Note 9)
V
IH
V
IL
V
OH
V
OL
I
L
I
L
Cin
I
DR
F
BC
T
BCP
T
CH
F
SYNC
T
SP
T
SH
T
SL
T
DSETUP
High level input voltage
Low level input voltage
High level output voltage
Low level output voltage
Input Leakage Current
Tri state Leakage Current
AC-Link I/O capacitance
Output drive current
BIT_CLK frequency
BIT_CLK period
BIT_CLK high
SYNC frequency
SYNC period
SYNC high pulse width
SYNC low pulse width
Setup Time for codec data input
SDATA_OUT to falling edge of BIT_CLK
Variation of BIT_CLK duty cycle from
50%
48
20.8
1.3
19.5
3.5
10
I
O
= −2.5 mA.
I
O
= 2.5 mA.
AC Link inputs
High impedance AC Link outputs
SDout, BitClk, SDin, Sync, Reset# only
AC Link outputs
4
5
12.288
81.4
0.65 x
DV
DD
0.35 x
DV
DD
0.90 x
DV
DD
0.10 x
DV
DD
V (min)
V (max)
V (min)
V (max)
µA
µA
pF (max)
mA
MHz
ns
±
10
±
10
7.5
Digital Timing Specifications
(Note 9)
±
20
% (max)
kHz
µs
µs
µs
ns (min)
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