TDA7476 데이터 시트보기 (PDF) - STMicroelectronics
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TDA7476 Datasheet PDF : 19 Pages
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TDA7476
1) The amplifier can drain current in the resistive path of the short circuit, hence this current and consequently
the short circuit resistor cannot be determined with a sufficient level of accuracy.
2) The voltage difference between the car radio ground (reference) and the position of the chassis of the car
where the loudspeaker line is connected (due to an accidental short circuit) can be up to some hundreds of
mV. This does not permit a correct measure of the short circuit resistor.
Turn-on diagnostic - AUX1, AUX2
To detect if there is a short circuit to GND or an open load involving to the AUX output of the car radio, the volt-
age across a sensing resistor Rsens is detected.These output voltages (for example for the active antenna and
for the booster) are usually generated by high side drivers, but also voltage regulators with Vout >5V are admis-
sible. The detection ranges can be set by adjusting the sensing resistors Rsens1 or Rsens2 as following:
S.C. to GND x Normal Operation x
Open Load
I1
I2
I3
I4
D01AU1258
I4
=
A-----O----L---,-m----a---x-
Rsens
I3
=
A-----n---o---p---,-m----i-n--
Rsens
I2
=
A-----n---o---p---,-m----a---x-
Rsens
I1
=
A-----g---n---d---,-m----i-n--
Rsens
Where AOL, Anop, Agnd are as specified in the ELECTRICAL CHARACTERISTICS.
For example, if Rsens = 5 Ohm, the following detection table will be operative :
S.C. to GND x Normal Operation x
Open Load
170mA 100mA
25mA 17mA
D96AU503
Permanent diagnostic - CH1, CH2, CH3, CH4, CH5 - Short to GND and Vs
During the CAR-RADIO normal operation, to detect a short circuit to GND (or to Vs), the output voltages are
sensed. If one or more outputs stay at any voltage below 0.8V or over Vs-0.6V for more than 2 sec. (typ), the
warning pin is pulled down.The µP can address the TDA7476 to know the status.The subsonic current pulse is
activated also in this case. The fault is correctly detected if it remains until the memorization (tm in fig.1).In this
phase, faults regarding shorts across the load and open loads cannot be detected.
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