TDA7476
CAR RADIO DIAGNOSTIC PROCESSOR
s
s
s
s
s
s
s
s
s
s
s
s
s
WIDE OPERATING VOLTAGE RANGE
ST-BY FUNCTION (C-MOS)
LOW QUIESCENT ST-BY CURRENT
CONSUMPTION
I
2
C BUS INTERFACE WITH 2 EXTERNALLY
SELECTABLE ADDRESSES
UP TO 5 BTL EQUIVALENT INPUTS FOR
FAULT DETECTION IN THE AUDIO
CHANNELS
- short to GND
- short to Vs
- short across the load (at turn-on)
- open load (at turn-on)
2 AUX INPUTS FOR FAULT DETECTION IN
THE ANTENNA AND BOOSTERS SUPPLY
LINE- short to GND- open load
WARNING PIN FUNCTION (interrupt facility)
ACTIVATED IN THE FOLLOWING
CONDITION:
- audio channel shorted to V
S
- audio channel shorted to GND
- aux input shorted to GND
NOISE FREE DIAGNOSTICS OPERATION
PROTECTORS
LOAD DUMP VOLTAGE
OPEN GND
REVERSED BATTERY
ESD
MULTIPOWER BCD TECHNOLOGY
SO-24
ORDERING NUMBER: TDA7476
DESCRIPTION
The car radio diagnostic processor is an interface
chip in BCD Technology intended for car radio appli-
cations. It is able to detect potential faults coming
from any misconnection in the car radio or in the har-
ness when installing the set.
The device is able to reveal any fault in the loud-
speaker lines and in the antenna and booster supply
lines, providing a proper output signal (I2C bus com-
patible) in order to disable the ICs under fault and/or
to alert the micro-controller by means of warning
messages.
PIN CONNECTION
(Top view)
GND
SDA
SCL
ADD
W
AUX1 OUT
AUX1 IN
AUX2 IN
AUX2 OUT
5V
ST-BY
V
S
1
2
3
4
5
6
7
8
9
10
11
12
D97AU570A
24
23
22
21
20
19
18
17
16
15
14
13
CH5-
CH5+
CH4+
CH4-
CH3-
CH3+
CH2+
CH2-
CH1-
CH1+
T-CAP
CSR
April 2001
1/19
TDA7476
BLOCK DIAGRAM & APPLICATION CIRCUIT
2
3
4
I C
2
SDA
SCL
ADD
V
S
C3
10µF
R3
10KΩ
W
C2
100nF
24
INTERFACE
23
22
21
20
19
CH3
CH4
CH5
12
5
DELAY
CURRENT
FORCING
&
COMPARATORS
VOLTAGE REGULATOR
&
TEST SIGNAL GENERATOR
18
17
16
15
6
RSENS1
7
CH1
OUT
AUX1
IN
IN
RSENS2
AUX2
OUT
D96AU499A
R4
10KΩ
ST-BY
SW1
5V
REF
C1
10∝F
11
10
14
13
C
T
R
CS
CH2
8
R5 51Ω
DIG-GND
1
9
PIN FUNCTION
N°
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15/16
17/18
19/20
21/22
23/24
Pin
GND
SDA
SCL
ADD
W
AUX1 OUT
AUX1 IN
AUX2 IN
AUX2 OUT
5V
ST-BY
V
S
CSR
T-CAP
CH1+/CH1-
CH2-/CH2+
CH3+/CH3-
CH4-/CH4+
CH5+/CH5-
Ground
Dta line
Clock line
Address select
Warning
AUX1 output
AUX1 input
AUX2 input
AUX2 output
5V-Regulator
Stand-by
Supply Voltage
Current setting resistor
Timing capacitor
Audio output - Channel 1
Audio output - Channel 2
Audio output - Channel 3
Audio output - Channel 4
Audio output - Channel 5
Description
2/19
TDA7476
ABSOLUTE MAXIMUM RATINGS
Symbol
V
op
V
s
V
peak
P
tot
T
stg
; T‘c-
V
SB
V
SDA
V
SCL
V
ADD
V
CH
Operating Supply Voltage
DC Supply Voltage
Peak Supply Voltage t = 50ms
Total Power Dissipation Tcase = 25°C
Storage and Junction Temperature
Stand-by Pin Voltage
SDA Pin Voltage
SCL Pin Voltage
ADD Pin Voltage
CH+ or CH- Pin Voltage
Parameter
Value
18
28
40
1.5
-40 to 150
6
6
6
6
min (*) (V
S
+10, 25)
Unit
V
V
V
W
°C
V
V
V
V
(*) Minimum value between V
S
+10V and 25V.
THERMAL DATA
Symbol
R
Th j-amb
Parameter
Thermal resistance junction to ambient
Max.
Value
85
Unit
°C/W
ELECTRICAL CHARACTERISTICS
(V
s
= 14.4V; T
amb
= 25°, unless otherwise specified.)
Symbol
V
SB
IN
Parameter
Stand-By IN Threshold
3.5
Stand-By Voltage Pin = 1.5V
Total quiescent Current with
TDA7476 not addressed
5
100
Test Condition
Min.
Typ.
Max.
1.5
Unit
V
V
µA
mA
V
SB
OUT Stand-By OUT Threshold
I
SB
I
q
Stand-By Current Consumption
Total Quiescent Current
AUDIO INPUTS CH1, CH2, CH3, CH4, CH5 - TURN ON DIAGNOSTIC
Pgnd
Short to GND det. (below this
limit, the Audio Output is
considerd in Short Circuit to
GND)
Short to Vs det. (above this limit,
the Audio Output is considered in
Short Circuit to Vs)
Normal operation thresholds.
(Within these limits, the Audio
Output is considered without
faults)
Power amplifier in st-by condition
0.8
V
Pvs
Vs-0.6
V
Pnop
1.2
Vs-1.2
V
3/19
TDA7476
ELECTRICAL CHARACTERISTICS
(continued)
(V
s
= 14.4V; T
amb
= 25°, unless otherwise specified.)
Symbol
Lsc
Parameter
Shorted Load det. (voltage across
the Audio Outputs). Below this
limit the load is considered
shorted.
Open Load det. (voltage across
the Audio Outputs). Above this
limit the load is considered open.
Normal load det. (Voltage across
the Audio Output). Within these
limits the load resistance is
considered normal.
Test Condition
Power amplifier in st-by condition
Min.
Typ.
Max.
5
Unit
mV
Lop
550
mV
Lnop
22
220
mV
AUX INPUTS AUX1, AUX2 - TURN ON DIAGNOSTIC
Agnd
Short to GND det. (voltage across
the sensing resistor). Above this
limit the AUX pin is considered in
Short Circuit to GND.
Open load det. (voltage across
the sensing resistor). Below this
limit the Aux pin is considered in
Open Load condition.
Normal Operation det. (Voltage
across the sensing resistor).
Within these limits the load
resistance connected to the Aux
pin is considered correct.
0.125
High side driver ON
0.85
V
Aol
0.085
V
Anop
0.5
V
AUDIO INPUTS - PERMANENT DIAGNOSTIC
Pgnd
Short to GND det. (below this
limit, the Audio Output is
considered in Short Circuit to Vs)
This condition must be true for a
time higher than Tdel
Short to Vs det. (above this limit
the Audio Output is considered in
Short Circuit to Vs) This condition
must be true for a time higher
than Tdel
Normal operation thresholds.
(Within these limits, the Audio
Output is considered without
faults)
Power amplifier ON
0.8
V
Pvs
Vs-0.6
V
Pnop
1.2
Vs-1.2
V
AUX INPUTS - PERMANENT DIAGNOSTIC
Agnd
Short to GND det. (above this
limit, the Audio Output is
considered in Short Circuit to Vs)
This condition must be true for a
time higher than Tdel
High side driver ON
0.85
V
4/19
TDA7476
ELECTRICAL CHARACTERISTICS
(continued)
(V
s
= 14.4V; T
amb
= 25°, unless otherwise specified.)
Symbol
Aol
Parameter
Open load det. (voltage across
the sensing resistor. Below this
limit the Aux pin is considered in
Open Load condition)This
condition must be true for a time
higher than Tdel
Normal Operation det. (Voltage
across the sensing resistor.
Within these limits the load
resistance connected to the Aux
pin is considered correct)
Test Condition
High side driver ON
Min.
Typ.
Max.
0.085
Unit
V
Anop
0.125
0.5
V
PERMANENT DIAGNOSTIC - ACQUISITION TIME DELAY
Tdel
Acquisition time delay - The fault
is considered true if the fault
condition are present for more
than Tdel without interruption
2
s
PERMANENT DIAGNOSTIC - WARNING PIN
V
sat
Saturation voltage on pin 5
Sink Current at Pin 5 = 1mA
1
V
ADDRESS SELECT
V
ADD
Voltage on pin 4
Address 0100010X
Address 0100011X
I
2
C BUS INTERFACE
f
SCL
V
IL
V
IH
V
SAT
Clock Frequency
Input Low Voltage
Input High Voltage
Sat Voltage at pin 2
Sink Current at Pin 2 = 5mA
3
1.5
400
1.5
KHz
V
V
V
3
1.5
5
V
V
WORKING PRINCIPLES
Turn-on diagnostic - CH1, CH2, CH3, CH4, CH5 -
Shorted load/open load detection
s
To detect a short across the load or an open
load, a subsonic current pulse is generated. The
information related to the status of the outputs is
measured and memorized at the top of the
current pulse (tm in fig.1). The current is
sourced by the positive pins (CH1+,...CH5+)
and it is sunk by the corresponding negative
pins (CH1-,...CH5-).
Figure 1.
I(mA)
I
SOURCE
I
SINK
t
m
D97AU571
t
s
t
(ms)
5/19
51单片机
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