HIGH PERFORMANCE SIGNAL PROCES-
SOR FOR CAR RADIO SYSTEMS
DEVICE INCLUDES AUDIO PROCESSOR,
STEREO DECODER, NOISEBLANKER AND
MULTIPATH DETECTOR
NO EXTERNAL COMPONENTS REQUIRED
FULLY PROGRAMMABLE VIA I
2
C BUS
LOW DISTORTION
LOW NOISE
DESCRIPTION
The TDA7461N is a high performance signal
processor specifically designed for car radio ap-
plications.
The device includes a complete audioprocessor
and
a
stereo
decoder
with
noiseblanker,
stereoblend and all signal processing functions
necessary for state-of-the-art as well as future car
radio systems.
Switched-capacitors design technique allows to
obtain all these features without external compo-
nents or adjustments. This means that higher
quality and reliability walks alongside an overall
cost saving.
The CSP is fully programmable by I
2
C bus inter-
face allowing to customize key device parameters
and especially filter characteristics.
The BICMOS process combined with the opti-
mized signal processing assure low noise and
low distortion performances.
June 2000
®
SUPPLY
LOUDNESS
DEMODULATOR
+ STEREO ADJUST
+ STEREO BLEND
CREF
MPIN
OUT LR
D97AU646A
DIGITAL CONTROL
PILOT
CANCELLATION
VS
CASS L
INPUT
MULTIPLEXER
+
AUTO ZERO
PH GND
BEEP
MPX
MIXING
STAGE
VOLUME
BASS
TREBLE
OUT LR
OUT LF
OUT RR
OUT RF
OUT LF
OUT RR
OUT RF
SCL
SDA
80KHz
LP
PLL
25KHz
LP
S & H
HIGH
CUT
CONTROL
MULTIPATH-
DETECTOR
PULSE
FORMER
D
MPOUT
LEVEL
CDL
CDG
CDR
AM
CASS R
PHONE
GND
SMUTE
PHONE
SOFT
MUTE
PIL
DET
I
2
C BUS
NOISE
BLANKER
A
MUX R
MUX L
ACOUTL
ACOUTR
ACINL
ACINR
7
6
5
10
3
4
9
8
11
21
20
26
13
14
12
23
25
22
24
18
19
16
15
2
1
27
28
17
BLOCK DIAGRAM
SO28
ORDERING NUMBER: TDA7461ND
TDA7461N
CAR RADIO SIGNAL PROCESSOR
1/31
ABSOLUTE MAXIMUM RATINGS
Symbol
Parameter
Value
Unit
V
S
Operating Supply Voltage
10.5
V
T
amb
Operating Ambient Temperature Range
-40 to 85
°
C
T
stg
Storage Temperature Range
-55 to 150
°
C
SUPPLY
Symbol
Parameter
Test Condition
Min.
Typ.
Max.
Unit
V
S
Supply Voltage
7.5
9
10
V
I
S
Supply Current
V
S
= 9V
25
30
35
mA
SVRR
Ripple Rejection @ 1KHz
Audioprocessor (all filters flat)
60
dB
Stereodecoder + Audioprocessor
45
dB
ESD
All pins are protected against ESD according to the MIL883 standard.
THERMAL DATA
Symbol
Parameter
Value
Unit
R
th-j pins
Thermal Resistance Junction-pins
Max
85
°
C/W
ACINL
ACINR
CASSR
CASSL
CDR
CDL
CDGND
PH GND
PHONE
GND
VS
OUTRR
OUTRF
OUTLR
OUTLF
CREF
ACOUTR
ACOUTL
1
3
2
4
5
6
7
8
9
26
25
24
23
22
20
21
19
27
10
28
AM
SDA
D97AU647
MPX
LEVEL
MPIN
MUXR
SMUTE
SCL
11
12
13
18
16
17
15
14
MPOUT
MUXL
PIN CONNECTION
TDA7461N
2/31
PIN DESCRIPTION
N.
Name
Function
Type
1
ACINL
Speaker Stage Input Left
I
2
ACINR
Speaker Stage Input Right
I
3
CASSR
Cassette Input Right
I
4
CASSL
Cassette Input Left
I
5
CDR
CD Right Channel Input
I
6
CDGND
Ground reference CD
I
7
CDL
CD Left Channel Input
I
8
PHGND
Phone Ground
I
9
PHONE
Phone Input
I
10
AM
AM Input
I
11
MPX
FM Input (MPX)
I
12
LEVEL
Level Input Stereodecoder
I
13
MPIN
Multipath Detector Input
I
14
MPOUT
Multipath Detector Output
O
15
MUXL
Multiplexer Output Left Channel (Stereodecoder Output left selectable
1
)
O
16
MUXR
Multiplexer Output Right Channel (Stereodecoder Output right selectable
1
)
O
17
SMUTE
Soft Mute Drive
I
18
SCL
I
2
C Clock Line
I/O
19
SDA
I
2
C Data Line
I/O
20
GND
Supply Ground
S
21
VS
Supply Voltage
S
22
OUTRR
Right Rear Speaker Output
O
23
OUTLR
Left Rear Speaker Output
O
24
OUTRF
Right Front Spaeaker Output
O
25
OUTLF
Left Front Speaker Output
O
26
CREF
Reference Capacitor Pin
S
27
ACOUTR
Pre-speaker AC Output Right Channel
O
28
ACOUTL
Pre-speaker AC Output Left Channel
O
(1) See databyte specification - speaker attenuators
Pin type legenda:
I = Input
O = Output
I/O = Input/Output
S = Supply
TDA7461N
3/31
AUDIO PROCESSOR PART
Input Multiplexer
Fully differential or quasi-differential CD and
cassette stereo input
AM mono or stereo input
Phone differential or single ended input
Internal beep with 2 frequencies (selectable)
Mixable phone and beep signals
Loudness
Second order frequency response
Programmable center frequency and quality factor
15 x 1dB steps
Selectable flat-mode (constant attenuation)
Volume control
1dB attenuator
Max. gain 20dB
Max. attenuation 79dB
Soft-step gain control
Bass Control
2nd order frequency response
Center frequency programmable in 4(5) steps
DC gain programmable
7 x 2dB steps
Treble Control
2nd order frequency response
Center frequency programmable in 4 steps
7 x 2dB steps
Speaker Control
4 independent speaker controls (1dB steps
control range 50dB)
Mute Functions
Direct mute
Digitally controlled softmute with 4 program-
mable time constants
ELECTRICAL CHARACTERISTICS (V
S
= 9V; T
amb
= 25
°
C; R
L
= 10K
Ω
; all gains = 0dB; f = 1KHz;
unless otherwise specified).
Symbol
Parameter
Test Condition
Min.
Typ.
Max.
Unit
INPUT SELECTOR
R
in
Input Resistance
all inputs except Phone
70
100
130
K
Ω
V
CL
Clipping Level
2.2
2.6
V
RMS
S
IN
Input Separation
80
100
dB
G
IN MIN
Min. Input Gain
-1
0
1
dB
G
IN MAX
Max. Input Gain
13
14
15
dB
G
STEP
Step Resolution
1
2
3
dB
V
DC
DC Steps
Adjacent Gain Step
-5
0
+5
mV
G
MIN
to G
MAX
-5
1
+5
mV
DIFFERENTIAL CD STEREO INPUT
R
in
Input Resistance
Differential
70
100
130
K
Ω
Common Mode
20
30
40
K
Ω
CMRR
Common Mode Rejection Ratio
V
CM
= 1
VRMS
@ 1KHz
45
70
dB
V
CM
= 1
VRMS
@ 10KHz
45
60
dB
e
N
Output Noise @ Speaker
Output
20Hz to 20KHz flat; all stages
0dB
9
15
µ
V
DIFFERENTIAL PHONE INPUT
R
in
Input Resistance
Differential
10
15
20
K
Ω
Common Mode
20
30
40
K
Ω
CMRR
Common Mode Rejection Ratio
V
CM
= 1
VRMS
@ 1KHz
45
70
dB
V
CM
= 1
VRMS
@ 10KHz
45
60
dB
TDA7461N
4/31
ELECTRICAL CHARACTERISTICS (continued)
Symbol
Parameter
Test Condition
Min.
Typ.
Max.
Unit
BEEP CONTROL
V
RMS
Beep Level
250
350
500
mV
f
BMIN
Lower Beep Frequency
570
600
630
Hz
f
BMAX
Higher Beep Frequency
1.15
1.2
1.25
KHz
MIXING CONTROL
M
LEVEL
Mixing Level
Source
-1
0
1
dB
Source
-5
-6
-7
dB
Source
-10
-12
-14
dB
Beep/Phone
-1
0
1
dB
VOLUME CONTROL
G
MAX
Max Gain
19
20
21
dB
A
MAX
Max Attenuation
-83
-79
-75
dB
A
STEP
Step Resolution
0.5
1
1.5
dB
E
A
Attenuation Set Error
G = -20 to 20dB
-1.25
0
1.25
dB
G = -60 to 20dB
-4
0
3
dB
E
T
Tracking Error
2
dB
V
DC
DC Steps
Adjacent Attenuation Steps
-3
0.1
3
mV
From 0dB to G
MIN
-7
0.5
+7
mV
LOUDNESS CONTROL
A
STEP
Step Resolution
0.5
1
1.5
dB
A
MAX
Max. Attenuation
-16
-15
-14
dB
f
CMIN
Lower Center Frequency
180
200
220
Hz
f
CMAX
Higher Center Frequency
360
400
440
Hz
SOFT MUTE
A
MUTE
Mute Attenuation
60
100
dB
T
D
Delay Time
T1
0.48
1
ms
T2
0.96
2
ms
T3
20
40.4
60
ms
T4
200
324
600
ms
V
THlow
Low Threshold for SM Pin
1
1
V
V
THhigh
High Threshold for SM Pin
2.5
V
R
PU
Internal Pull-up Resistor
70
100
130
K
Ω
V
PU
Pull-up Voltage
4.7
V
SOFT STEP
T
SW
Switch Time
5
10
15
ms
1) The SM pin is active low (Mute = 0)
TDA7461N
5/31
ELECTRICAL CHARACTERISTICS (continued)
Symbol
Parameter
Test Condition
Min.
Typ.
Max.
Unit
BASS CONTROL
C
RANGE
Control Range
±
13
±
14
±
15
dB
A
STEP
Step Resolution
1
2
3
dB
f
C
Center Frequency
f
C1
54
60
66
Hz
f
C2
63
70
77
Hz
f
C3
72
80
88
Hz
f
C4
90
100
(2)
110
Hz
Q
BASS
Quality Factor
Q
1
0.9
1
1.1
Q
2
1.1
1.25
1.4
Q
3
1.3
1.5
1.7
Q
4
1.8
2
2.2
DC
GAIN
Bass-Dc-Gain
DC = off
-1
0
+1
dB
DC = on
4
4.4
6
dB
TREBLE CONTROL
C
RANGE
Control Range
±
13
±
14
±
15
dB
A
STEP
Step Resolution
1
2
3
dB
f
C
Center Frequency
f
C1
8
10
12
KHz
f
C2
10
12.5
15
KHz
f
C3
12
15
18
KHz
f
C4
14
17.5
21
KHz
SPEAKER ATTENUATORS
C
RANGE
Control Range
-53
-50
-47
dB
A
STEP
Step Resolution
0.5
1
2
dB
A
MUTE
Output Mute Attenuation
80
90
dB
E
E
Attenuation Set Error
-2
2
dB
V
DC
DC Steps
Adjacent Attenuation Steps
0.1
5
mV
AUDIO OUTPUTS
V
CLIP
Clipping Level
d = 0.3%
2.2
2.6
V
RMS
R
L
Output Load Resistance
2
K
Ω
C
L
Output Load Capacitance
10
nF
R
OUT
Output Impedance
30
100
Ω
V
DC
DC Voltage Level
3.6
3.8
4.0
V
GENERAL
e
NO
Output Noise
BW = 20 Hz to 20 KHz
output muted
3
15
µ
V
BW = 20 Hz to 20 KHz
all gain = 0dB
6.5
15
µ
V
S/N
Signal to Noise Ratio
all gain = 0dB flat; V
O
= 2V
RMS
106
dB
bass treble at 12dB; V
O
=
2.6V
RMS
100
dB
d
Distortion
V
IN
= 1V
RMS
; all stages 0dB
0.002
0.1
%
V
IN
= 1V
RMS
; Bass & Treble = 12dB
0.05
0.1
%
S
C
Channel separation Left/Right
80
100
dB
E
T
Total Tracking Error
A
V
= 0 to -20dB
-1
0
1
dB
A
V
= -20 to -60dB
-2
0
2
dB
2) See description of Audioprocessor Part - Bass & Treble filter characteristics programming
TDA7461N
6/31
DESCRIPTION OF THE AUDIOPROCESSOR
PART
Programmable Input Matrix
The programmable input matrix of the TDA7461N
offers several possibilities to adapt the audioproc-
essor to the desired application. In to the stand-
ard application we have:
CD quasi differential
Cassette stereo
Phone differential
AM mono
Stereodecoder input.
The input matrix can be configured by only 2 bits:
bits 3 and 4 of subaddress 0. Basically the bit of
subaddress 13 is fixed by the application and has
to be programmed only once at the startup of the
IC.
For many configurations the two bits are also
fixed during one application (e.g. the standard ap-
plication) and a change of the input source can
be done by loading the first three bits of subad-
dress 0.
In other configurations for some sources a pro-
gramming of bit 3 and 4 of subaddress 0 is nec-
essary in addition to the three source selection
bits. In every case only the subaddress 0 has to
be changed to switch from one source to another.
The following picture shows the input and source
programming flow:
TDA7461
CD QD
CD FD
APPL. 2
APPL. 1
APPL. 3
APPL. 5
APPL. 4
APPL. 6
CD QD
CASSETTE
FM STD
AM MONO
PHONE (D)
CD QD
CASSETTE
FM STD
AM STEREO
PHONE (SE)
CD QD
CASSETTE
FM STD
AM STD
PHONE (D)
CD FD
CASSETTE
FM STD
AM MONO
PHONE (SE)
CD FD
CASSETTE
FM STD
AM STEREO
CD FD
CASSETTE
FM STD
AM STD
PHONE (SE)
D97AU632B
Figure 1. Input Configuration Tree
Note: in AMSTD configuration the AM mono signal is lead through the FM stereodecoder part to use its additional filters and high-cut function.
TDA7461N
7/31
How to find the right input configuration
The best way to come to the desired configura-
tion may be to go through the application tree
from the top to the bottom while making the spe-
cific decisions.
This way will lead to one of the six possible appli-
cations. Then take the number of the application
and go into the pinning table. Here you will find
the special pinout as well as the special program-
ming codes for selecting sources.
For example in Appl. 6 the TDA7461N has to be
configured
while
startup
with
the databyte
0/xxxx0xxx.
To select the FM, AM or phone source the last
five significant bits of subaddress 0 have to be
changed, for any other source the last three bits
are sufficient (see data byte specification).
Input stages
Most of the input circuits are the same as in pre-
ceeding ST audioprocessors with exception of
the CD inputs (see figure 2).
In the meantime there are some CD players in
the market having a significant high source im-
pedance which affects strongly the common-
mode rejection of the normal differential input
stage. The additional buffer of the CD input
avoids this drawback and offers the full common-
mode rejection even with those CD players.
The TDA7461N can be configured with an addi-
tional input; if the AC coupling before the speaker
stage is not used (bit 7 in subaddress 5 set to ”1”)
ACINL and ACINR pins can be used as an addi-
tional stereo input.
AutoZero
In order to reduce the number of pins there is no
AC coupling between the In-Gain and the follow-
ing stage, so that any offset generated by or be-
fore the In-Gain stage would be transferred or
even amplified to the output.
To avoid that effect a special offset cancellation
stage called AutoZero is implemented.
To avoid audible clicks the audioprocessor is
muted before the loudness stage during this time.
In some cases, for example if the
µ
P is executing
a refresh cycle of the I
2
C bus programming, it is
not useful to start a new AutoZero action because
no new source is selected and an undesired mute
would appear at the outputs. For such applica-
tions the TDA7461N could be switched in the
”Auto Zero Remain” mode (Bit 6 of the subad-
dress byte). If this bit is set to high, the DAT-
ABYTE 0 could be loaded without invoking the
AutoZero and the old adjustment value remains.
PIN NUMBER
Appl. No
6
8
9
10
Programming
1)
1
CD
GND
Phone
GND
Phone
AM
MONO
Startup:
0/xxx11xxx
2
CD
GND
Phone