TDA7476
4/19
Lsc Shorted Load det. (voltage across
the Audio Outputs). Below this
limit the load is considered
shorted.
Power amplifier in st-by condition 5 mV
Lop Open Load det. (voltage across
the Audio Outputs). Above this
limit the load is considered open.
550 mV
Lnop Normal load det. (Voltage across
the Audio Output). Within these
limits the load resistance is
considered normal.
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.
High side driver ON 0.85 V
Aol Open load det. (voltage across
the sensing resistor). Below this
limit the Aux pin is considered in
Open Load condition.
0.085 V
Anop Normal Operation det. (Voltage
across the sensing resistor).
Within these limits the load
resistance connected to the Aux
pin is considered correct.
0.125 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
Power amplifier ON 0.8 V
Pvs 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
Vs-0.6 V
Pnop Normal operation thresholds.
(Within these limits, the Audio
Output is considered without
faults)
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
ELECTRICAL CHARACTERISTICS
(continued)
(V
s
= 14.4V; T
amb
= 25°, unless otherwise specified.)
Symbol Parameter Test Condition Min. Typ. Max. Unit
5/19
TDA7476
Aol 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
High side driver ON 0.085 V
Anop Normal Operation det. (Voltage
across the sensing resistor.
Within these limits the load
resistance connected to the Aux
pin is considered correct)
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
2s
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 1.5 V
Address 0100011X 3 5 V
I
2
C BUS INTERFACE
f
SCL
Clock Frequency 400 KHz
V
IL
Input Low Voltage 1.5 V
V
IH
Input High Voltage 3 V
V
SAT
Sat Voltage at pin 2 Sink Current at Pin 2 = 5mA 1.5 V
ELECTRICAL CHARACTERISTICS
(continued)
(V
s
= 14.4V; T
amb
= 25°, unless otherwise specified.)
Symbol Parameter Test Condition Min. Typ. Max. Unit
WORKING PRINCIPLES
Turn-on diagnostic - CH1, CH2, CH3, CH4, CH5 -
Shorted load/open load detection
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.
t
m
t
s
t
(ms)
I
SOURCE
I
SINK
I(mA)
D97AU571
TDA7476
6/19
Isink and Isource are depending on the external resistor Rcs. The minimum allowed value for Rcs is
1.65KOhm. The relationship among Isink, Isource and Rcs is the following:
Isink = (3.3/Rcs) · 11
Isource = 1.5 · Isink
On bridge (or bridge equivalent) devices if there is no short circuit to GND or to Vs, Isource goes into
saturation mode (for Vout > 3V), and in the load flows Isink. As the turn-on diagnostic thresholds are
fixed, it is possible to calculate the ranges of loudspeaker resistance in which short circuit (S.C.), normal
operation and open load are detected as following:
where L
sc
, L
nop
, L
op
as specified in the ELCTRICAL CHARACTERISTICS.
For example, here below are two cases, with Rcs = 3.3KOhm and Rcs = 1.8KOhm..
The exact values of the above mentioned resistive ranges may vary a little, depending on the power amplifier
used.
Turn-on diagnostic - CH1, CH2, CH3, CH4, CH5 - Short to GND and Vs
.
To detect if there is short circuit to GND or Vs, the subsonic current pulse is exploited. The information related
to the status of the outputs are measured and memorized at the top of the current pulse (tm in fig.1). If no faults
are present, the pins connected to the audio outputs (CH1,..CH5) will reach about 3V.If one or more outputs are
shorted to GND, these voltages become lower than 3V.If one or more outputs are shorted to Vs, the output volt-
age increases over 3V.The fault status can be know by sensing the output voltages. The reason way voltage
threshold has been preferred instead of a current threshold to declare short circuit resistor ranges is two fold:
S.C. across Load x Open Load
0 R
2
R
3
infinite
xNormal Load
R
1
R
4
D01AU1256
R1
L
sc,max
I
ksin
-------------------
L
sc,max
36.3
-------------------
R
cs
==
R2
L
nop,min
I
ksin
----------------------
L
nop,min
36.3
----------------------
R
cs
==
R3
L
nop,max
I
ksin
-----------------------
L
nop,max
36.3
-----------------------
R
cs
==
R3
L
op,max
I
ksin
--------------------
L
op min,
36.3
--------------------
R
cs
==
S.C. across Load x Open Load
0 1.1 11 infinite
xNormal Operation
0.24 27
D96AU500A
S.C. across Load x Open Load
0 2 20 infinite
xNormal Operation
0.45 50

E-TDA7476013TR

Mfr. #:
Manufacturer:
STMicroelectronics
Description:
Audio DSPs CAR RADIO DIAG PROCESSOR
Lifecycle:
New from this manufacturer.
Delivery:
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