TDA7476 Datasheet, PDF (4/15 Pages) STMicroelectronics – CAR RADIO DIAGNOSTIC PROCESSOR

TDA7476
ELECTRICAL CHARACTERISTICS (continued)
Symbol
Parameter
Test Condition
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
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
Anop
Normal Operation det. (Voltage
across the sensing resistor.
Within these limits the load
resistance connected to the Aux
pin is considered correct)
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
PERMANENT DIAGNOSTIC - WARNING PIN
Vsat
Saturation voltage on pin 5
Sink Current at Pin 5 = 1mA
ADDRESS SELECT
VADD
Voltage on pin 4
Address 0100010X
I²C BUS INTERFACE
Address 0100011X
fSCL
Clock Frequency
VIL
Input Low Voltage
VIH
InputHigh Voltage
VSAT
Sat Voltage at pin 2
Sink Current at Pin 2 = 5mA
Min. Typ. Max. Unit
0.75
V
0.085 V
0.125
0.5
V
2
s
1
V
1.5
V
3
5
V
400 KHz
1.5
V
3
V
1.5
V
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 infor-
mation related to the status of the outputs are 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)
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) x 11
Isource = 1.5 x Isink
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