E-TDA7476 STMicroelectronics, E-TDA7476 Datasheet - Page 6

• Manufacturer Part Number: E-TDA7476
• Description: IC PROCESSOR RADIO DIAGN 24-SOIC
• Manufacturer: STMicroelectronics
• Type: Audio Processorr

Specifications of E-TDA7476

• Applications: Automotive Audio
• Mounting Type: Surface Mount
• Package / Case: 24-SOIC (7.5mm Width)
• Operating Temperature (min): -40C
• Operating Temperature Classification: Automotive
• Mounting: Surface Mount
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

TDA7476
where L
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:
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:
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:
sc
, L
nop
, L
op
0
0
as specified in the ELCTRICAL CHARACTERISTICS.
0
S.C. across Load
S.C. across Load
S.C. across Load
0.45
0.24
R3
R2
R3
R1
R
1
=
=
=
x
x
=
x
L
---------------------- -
Isink = (3.3/Rcs) · 11
L
--------------------- -
1.1
Isource = 1.5 · Isink
L
------------------- -
L
------------------ -
no p,max
2
no p,min
R
I
Normal Operation
Normal Operation
op ,max
I
s c,max
I
I
sin
sin
sin
2
sin
Normal Load
k
k
k
k
=
=
=
=
L
------------------ - R
L
--------------------- - R
L
---------------------- - R
L
------------------- - R
sc ,max
nop ,min
no p,max
op min
36.3
36.3
36.3
36.3
R
20
11
3
x
x
x
cs
cs
50
27
c s
c s
R
4
Open Load
Open Load
Open Load
D01AU1256
D96AU500A
infinite
infinite
infinite