Diagnostics functional description

TDA7566

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disconnected, because the remaining speaker (woofer) would be out of its operating range

(high impedance). The diagnostic decision is made according to peak output current

thresholds, as follows:

Iout > 500mApk = NORMAL STATUS

Iout < 250mApk = OPEN TWEETER

To correctly implement this feature, it is necessary to briefly provide a signal tone (with the

amplifier in "play") whose frequency and magnitude are such to determine an output current

higher than 500mApk in normal conditions and lower than 250mApk should the parallel

tweeter be missing. The test has to last for a minimum number of 3 sine cycles starting from

(measuring period). To confirm presence of tweeter, it is necessary to find at least 3 current

pulses over 500mA over all the measuring period, else an "open tweeter" message will be

issued.

The frequency / magnitude setting of the test tone depends on the impedance

characteristics of each specific speaker being used, with or without the tweeter connected

(to be calculated case by case). High-frequency tones (> 10 KHz) or even ultrasonic signals

are recommended for their negligible acoustic impact and also to maximize the impedance

module's ratio between with tweeter-on and tweeter-off.

Figure 24 shows the Load Impedance as a function of the peak output voltage and the

relevant diagnostic fields.

This feature is disabled if any overloads leading to activation of the short-circuit protection

occurs in the process.

Figure 24.

Current detection: Load impedance magnitude |Z| Vs. output peak voltage of

the sinus

4.5

Multiple faults

When more misconnections are simultaneously in place at the audio outputs, it is

guaranteed that at least one of them is initially read out. The others are notified after

This is true for both kinds of diagnostic (Turn on and Permanent).

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Vout (Peak)

Load |z| (Ohm)

Iout (peak) <250mA

Iout (peak) >500mA

Low current detection area

(Open load)

D5 = 1 of the DBx byres

High current detection area

(Normal load)

D5 = 0 of the DBx bytes