LM4550
AC '97 Rev 2.1 Multi-Channel Audio Codec with Stereo
Headphone Amplifier, Sample Rate Conversion and
National 3D Sound
General Description
The LM4550 is an audio codec for PC systems which is fully
PC99 compliant and performs the analog intensive functions
of the AC97 Rev2.1 architecture. Using 18-bit Sigma-Delta
A/D's and D/A's, the LM4550 provides 90 dB of Dynamic
Range.
The LM4550 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 A/D's and D/A's
and an analog mixer with 4 stereo and 3 mono inputs, each
of which has separate gain, attenuation and mute control.
The LM4550 provides a stereo headphone amplifier with an
independent gain control and also supports National's 3D
Sound stereo enhancement and variable sample rate con-
version. The sample rate for the A/D and D/A can be pro-
grammed separately with a resolution of 1 Hz to convert any
rate between 4 kHz48 kHz.
The LM4550 features the ability to connect several codecs
together in a system to provide up to six channels for sur-
round sound applications. Multiple codec systems can be
built using the standard AC-Link format of one serial data
stream per codec, or using a unique National Semiconductor
feature for chaining codecs together. This chain feature re-
quires only a single data stream to the controller.
The AC97 architecture separates the analog and digital func-
tions of the PC audio system allowing both for system design
flexibility and increased performance.
Key Specifications
n
Analog Mixer Dynamic Range
97dB (typ)
n
D/A Dynamic Range
89dB (typ)
n
A/D Dynamic Range
90dB (typ)
n
Headphone Amp THD+N at 50 mW
0.02% (typ)
into 32
Features
n
AC'97 Rev 2.1 compliant
n
Several LM4550s can be combined together for up to 6
channel operation
n
Unique National chaining function allows multiple codecs
to be connected serially and use only a single controller
SDATA_IN pin
n
High quality Sample Rate Conversion (SRC) from 4 kHz
to 48 kHz in 1 Hz increments.
n
Stereo headphone amp with separate gain control
n
National's 3D Sound circuitry
n
External Amplifier Power Down (EAPD) control from
codec
n
PC-Beep passthrough to Line Out while reset is held
active low
n
Digital 3.3V and 5V compliant
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
2, 4, or 6 channel systems
December 2002
LM4550
AC
'97
Rev
2.1
Multi-Channel
Audio
Codec
with
Stereo
Headphone
Amplifier
,
Sample
Rate
Conversion
and
National
3D
Sound
2002 National Semiconductor Corporation
DS100972
www.national.com
Block
Diagram
10097201
LM4550
www.national.com
2
Absolute Maximum Ratings
(Note 3)
If Military/Aerospace specified devices are required,
please contact the National Semiconductor Sales Office/
Distributors for availability and specifications.
Supply Voltage
6.0V
Storage Temperature
-65C to +150C
Input Voltage
-0.3V to V
DD
+0.3V
ESD Susceptibility (Note 5)
2000V
pin 3
750V
ESD Susceptibility (Note 6)
200V
pin 3
100V
Junction Temperature
150C
Soldering Information
LQFP Package
Vapor Phase (60 sec.)
215C
Infrared (15 sec.)
220C
See AN-450 "Surface Mounting and their Effects on
Product Reliability" for other methods of
soldering surface mount devices.
JA
(typ) -- VBH48A
74C/W
Operating Ratings
Temperature Range
T
MIN
T
A
T
MAX
-40C
T
A
85C
Analog Supply Range
4.2V
AV
DD
5.5V
Digital Supply Range
3.0V
DV
DD
5.5V
Electrical Characteristics
(Notes 1, 3) The following specifications apply for AV
DD
= 5V, DV
DD
= 5V, Fs =
48kHz, single codec configuration, unless otherwise noted. Limits apply for T
A
= 25C. The reference for 0dB is 1Vrms unless
otherwise specified.
Symbol
Parameter
Conditions
LM4550
Units
(Limits)
Typical
(Note 7)
Limit
(Note 8)
AV
DD
Analog Supply Range
4.2
V (min)
5.5
V (max)
DV
DD
Digital Supply Range
3.0
V (min)
5.5
V (max)
D
IDD
Digital Quiescent Power Supply
Current
D
VDD
= 5V
43
mA
D
VDD
= 3.3V
20
mA
A
IDD
Analog Quiescent Power Supply
Current
53
mA
I
DSD
Digital Shutdown Current
500
A
I
ASD
Analog Shutdown Current
30
A
V
REF
Reference Voltage
2.23
V
PSRR
Power Supply Rejection Ratio
40
dB
Analog Loopthru Mode
Dynamic Range (Note 2)
CD Input to Line Output, -60dB Input
THD+N, A-Weighted
97
90
dB (min)
THD
Total Harmonic Distortion
V
O
= -3dB, f = 1kHz, R
L
= 10k
0.01
0.02
% (max)
Analog Input Section
V
IN
Line Input Voltage
1
Vrms
Mic Input with 20dB Gain
0.1
Vrms
Mic Input with 0dB Gain
1
Vrms
Xtalk
Crosstalk
CD Left to Right
-95
dB
Z
IN
Input Impedance(Note 2)
40
10
k
(min)
C
IN
Input Capacitance
15
pF
Interchannel Gain Mismatch
CD Left to Right
0.01
dB
Record Gain Amplifier - A/D
A
S
Step Size
0dB to 22.5dB
1.5
dB
Mixer Section
A
S
Step Size
+12dB to -34.5dB
1.5
dB
A
M
Mute Attenuation
86
dB
LM4550
www.national.com
3
Electrical Characteristics
(Notes 1, 3) The following specifications apply for AV
DD
= 5V, DV
DD
= 5V, Fs =
48kHz, single codec configuration, unless otherwise noted. Limits apply for T
A
= 25C. The reference for 0dB is 1Vrms unless
otherwise specified. (Continued)
Symbol
Parameter
Conditions
LM4550
Units
(Limits)
Typical
(Note 7)
Limit
(Note 8)
Analog to Digital Converters
Resolution
18
Bits
Dynamic Range (Note 2)
-60dB Input THD+N, A-Weighted
90
86
dB (min)
Frequency Response
-1dB Bandwidth
20
kHz
Digital to Analog Converters
Resolution
18
Bits
Dynamic Range (Note 2)
-60dB Input THD+N, A-Weighted
89
85
dB (min)
THD
Total Harmonic Distortion
V
IN
= -3dB, f=1kHz, R
L
= 10k
0.01
%
Frequency Response
20 - 21k
Hz
Group Delay (Note 2)
2
mS (max)
Out of Band Energy
-40
dB
Stop Band Rejection
70
dB
D
T
Discrete Tones
-96
dB
Output Volume and Amplifier Section
A
S
Step Size
0dB to -46.5dB
1.5
dB
A
M
Mute Attenuation
86
dB
THD+N
Headphone Amplifier Total Harmonic
Distortion plus Noise
Loop thru Mode R
L
=32, F=1KHz,
P
out
=50mW
0.02
%
Digital I/O (Note 2)
V
IL
Low level input voltage
0.30 x
DVDD
V (max)
V
HI
High level input voltage
0.40 x
DVDD
V (min)
V
OH
High level output voltage
0.50 x
DVDD
V (min)
V
OL
Low level output voltage
0.20 x
DVDD
V (max)
I
L
Input Leakage Current
AC Link inputs
10
A
I
L
Tri state Leakage Current
High impedance AC Link outputs
10
A
I
DR
Output drive current
AC Link outputs
5
mA
Digital Timing Specifications (Note 2)
F
BC
BIT_CLK frequency
12.288
MHz
T
BCP
BIT_CLK period
81.4
nS
T
CH
BIT_CLK high
Variation of BIT_CLK period from 50%
duty cycle
20
% (max)
F
SYNC
SYNC frequency
48
kHz
T
SP
SYNC period
20.8
S
T
SH
SYNC high pulse width
1.3
S
T
SL
SYNC low pulse width
19.5
S
T
SETUP
Setup Time
SDATA_IN, SDATA_OUT to falling edge
of BIT_CLK
15
nS (min)
T
HOLD
Hold Time
Hold time of SDATA_IN, SDATA_OUT
from falling edge of BIT_CLK
5
nS (min)
T
RISE
Rise Time
BIT_CLK, SYNC, SDATA_IN or
SDATA_OUT
6
nS (max)
LM4550
www.national.com
4
Electrical Characteristics
(Notes 1, 3) The following specifications apply for AV
DD
= 5V, DV
DD
= 5V, Fs =
48kHz, single codec configuration, unless otherwise noted. Limits apply for T
A
= 25C. The reference for 0dB is 1Vrms unless
otherwise specified. (Continued)
Symbol
Parameter
Conditions
LM4550
Units
(Limits)
Typical
(Note 7)
Limit
(Note 8)
T
FALL
Fall Time
BIT_CLK, SYNC, SDATA_IN or
SDATA_OUT
6
nS (max)
T
RST_LOW
RESET# active low pulse width
For cold reset
1.0
S (min)
T
RST2CLK
RESET# inactive to BIT_CLK start up
For cold reset
162.8
nS (min)
T
SH
SYNC active high pulse width
For warm reset
1.3
S
T
SYNC2CLK
SYNC inactive to BIT_CLK start up
For warm reset
162.8
nS (min)
T
SU2RST
Setup to trailing edge of RESET#
For ATE Test Mode
15
nS (min)
T
RST2HZ
Rising edge of RESET# to Hi-Z
For ATE Test Mode
25
nS (max)
Note 1: All voltages are measured with respect to the ground pin, unless otherwise specified.
Note 2: These specifications are guaranteed by design and characterization; they are not production tested.
Note 3: 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 4: The maximum power dissipation must be derated at elevated temperatures and is dictated by T
JMAX
,
JA
, and the ambient temperature T
A
. The maximum
allowable power dissipation is P
DMAX
= (T
JMAX
T
A
)/
JA
or the number given in Absolute Maximum Ratings, whichever is lower. For the LM4550, T
JMAX
= 150C.
The typical junction-to-ambient thermal resistance is 74C/W for package number VBH48A.
Note 5: Human body model, 100 pF discharged through a 1.5 k
resistor.
Note 6: Machine Model, 220 pF240 pF discharged through all pins.
Note 7: Typicals are measured at 25C and represent the parametric norm.
Note 8: Limits are guaranteed to National's AOQL (Average Outgoing Quality Level).
LM4550
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5
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