TDA7564 Datasheet TDA7564 | P10-P12

Obsolete Product(s) - Obsolete Product(s)

TDA7564

10/20

The information related to the outputs status is read and memorized at the end of the current pulse top. The

acquisition time is 100 ms (typ.). No audible noise is generated in the process. As for SHORT TO GND / Vs the

fault-detection thresholds remain unchanged from 26 dB to 12 dB gain setting. They are as follows:

Concerning SHORT ACROSS THE SPEAKER / OPEN SPEAKER, the threshold varies from 26 dB to 12 dB

gain setting, since different loads are expected (either normal speaker's impedance or high impedance). The

values in case of 26 dB gain are as follows:

If the Line-Driver mode (Gv= 12 dB and Line Driver Mode diagnostic = 1) is selected, the same thresholds will

change as follows:

b) PERMANENT DIAGNOSTICS.

Detectable conventional faults are:

– SHORT TO GND

– SHORT TO Vs

– SHORT ACROSS THE SPEAKER

The following additional features are provided:

– OUTPUT OFFSET DETECTION

The TDA7564 has 2 operating statuses:

1 RESTART mode. The diagnostic is not enabled. Each audio channel operates independently from each

other. If any of the a.m. faults occurs, only the channel(s) interested is shut down. A check of the output

status is made every 1 ms (fig. 19). Restart takes place when the overload is removed.

2 DIAGNOSTIC mode. It is enabled via I

C bus and self activates if an output overload (such to cause

the intervention of the short-circuit protection) occurs to the speakers outputs. Once activated, the di-

agnostics procedure develops as follows (fig. 20):

– To avoid momentary re-circulation spikes from giving erroneous diagnostics, a check of the output sta-

tus is made after 1ms: if normal situation (no overloads) is detected, the diagnostic is not performed and

the channel returns back active.

– Instead, if an overload is detected during the check after 1 ms, then a diagnostic cycle having a duration

of about 100 ms is started.

D01AU1253

S.C. to GND x S.C. to Vs

0V 1.8V V

-1.8V V

xNormal Operation

1.2V V

-1.2V

S.C. across Load x Open Load

0V 1.75Ω 45Ω Infinite

xNormal Operation

0.5Ω

85Ω

D01AU1327

D02AU1340

S.C. across Load x Open Load

0Ω 7Ω 180Ω infinite

xNormal Operation

2Ω 330Ω

Obsolete Product(s) - Obsolete Product(s)

11/20

TDA7564

– After a diagnostic cycle, the audio channel interested by the fault is switched to RESTART mode. The

relevant data are stored inside the device and can be read by the microprocessor. When one cycle has

terminated, the next one is activated by an I

C reading. This is to ensure continuous diagnostics

throughout the car-radio operating time.

– To check the status of the device a sampling system is needed. The timing is chosen at microprocessor

level (over half a second is recommended).

Figure 19. Restart timing without Diagnostic Enable (Permanent) - Each 1mS time, a sampling of

the fault is done

Figure 20. Restart timing with Diagnostic Enable (Permanent)

OUTPUT DC OFFSET DETECTION

Any DC output offset exceeding ±2V are signalled out. This inconvenient might occur as a consequence of ini-

tially defective or aged and worn-out input capacitors feeding a DC component to the inputs, so putting the

speakers at risk of overheating.

This diagnostic has to be performed with low-level output AC signal (or Vin = 0).

The test is run with selectable time duration by microprocessor (from a "start" to a "stop" command):

– START = Last reading operation or setting IB1 - D5 - (OFFSET enable) to 1

– STOP = Actual reading operation

Excess offset is signalled out if persistent throughout the assigned testing time. This feature is disabled if any

overloads leading to activation of the short-circuit protection occurs in the process.

AC DIAGNOSTIC.

It is targeted at detecting accidental disconnection of tweeters in 2-way speaker and, more in general, presence

of capacitively (AC) coupled loads.

This diagnostic is based on the notion that the overall speaker's impedance (woofer + parallel tweeter) will tend

to increase towards high frequencies if the tweeter gets disconnected, because the remaining speaker (woofer)

would be out of its operating range (high impedance). The diagnostic decision is made according to peak output

1-2mS

1mS 1mS 1mS

1mS

Overcurrent and short

circuit protection intervention

(i.e. short circuit to GND)

Short circuit removed

Out

Overcurrent and short

circuit protection intervention

(i.e. short circuit to GND)

Short circuit removed

1-2mS 100/200mS 1mS1mS

Obsolete Product(s) - Obsolete Product(s)

TDA7564

12/20

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 con-

ditions and lower than 250mApk should the parallel tweeter be missing. The test has to last for a minimum num-

ber of 3 sine cycles starting from the activation of the AC diagnostic function IB2<D2>) up to the I2C reading of

the results (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.

Fig. 21 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 21. Current detection: Load impedance magnitude |Z| vs. output peak voltage of the sinus

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 successive cycles of I

C reading and faults removal,

provided that the diagnostic is enabled. This is true for both kinds of diagnostic (Turn on and Permanent).

The table below shows all the couples of double-fault possible. It should be taken into account that a short circuit

with the 4 ohm speaker unconnected is considered as double fault.

Double fault table for Turn On Diagnostic

S. GND (so) S. GND (sk) S. Vs S. Across L. Open L.

S. GND (so) S. GND S. GND S. Vs + S. GND S. GND S. GND

S. GND (sk) / S. GND S. Vs S. GND Open L. (*)

S. Vs / / S. Vs S. Vs S. Vs

S. Across L. / / / S. Across L. N.A.

Open L. / / / / Open L. (*)

12345678

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

Obsolete Product(s) - Obsolete Product(s)

P1-P3 P4-P6 P7-P9 P10-P12 P13-P15 P16-P18 P19-P20

TDA7564

Mfr. #:

Buy TDA7564

Manufacturer:

STMicroelectronics

Description:

Audio Amplifiers Quad Power Amplifier

Lifecycle:

New from this manufacturer.

Delivery:

DHL FedEx Ups TNT EMS

Payment:

T/T Paypal Visa MoneyGram Western Union

Products related to this Datasheet

TDA7564